Two Ni(Co)CrAlY coatings were deposited by EB-PVD method on a DS superalloy of Ni-Al-Cr-Co-W-Mo-Ta-Hf system. SEM, XEDS and XRD were used to study the oxidation behavior of the coatings. The two coatings show a good protection for the DS superalloy. The results of the isothermal oxidation test at 1 150 ℃ for 100 h show that the oxidation tendency obeys the parabolic law, and the oxidation rate constant K_p of the coated specimens decreases to about 1/3 of that for the bare superalloy. After oxidation, a continuous alumina-based scale is formed at the surfaces of the coated samples. Y₂O₃, NiO and SiO₂ are also detectable in the oxide scale. A large number of Al in the coating is consumed due to high-temperature diffusion and oxidation reactions, and the NiAl phases in the coating are almost completely transformed to Ni₃Al phases. For the Hf-bearing coating, some HfO₂ particles exist at the interface between the coating and the substrate. Although internal oxidation occurs, the coating still shows a good adhesion with the superalloy substrate even after oxidation for 100 h. For the bare DS superalloy, after 100 h oxidation at 1 150 ℃, only discontinuous alumina-based oxide particles exist on the surface. Oxide spallation occurs for the bare alloy.

Graphite and Al₂O₃ short fibers reinforced Mg-Al-Zn alloy hybrid composites were fabricated by perform squeeze-infiltration route. The effects of the volume of graphite particles on the microstructure, mechanical properties and tribological behavior were investigated under the conditions of constant size of graphite particle and volume of Al₂O₃ short fiber. The results reveal that the uniform distribution of the reinforced graphite particles and Al₂O₃ short fiber can be obtained by this technique, and they have strong bonding with the metal matrix. Increasing graphite volume results in decrease in hardness, the ultimate tensile strength whereas the Al₂O₃ short fiber makes contribution to the increase in hardness of the composite. The composite exhibits good wear resistance, small wear mass loss and low coefficient of friction as compared with the metal matrix. The wear mechanisms transit from oxidation wear, abrasion wear into delamination wear as the applied load is increased, and a film of lubricant covering almost entire surface of specimen, is found to be formed, which separates the wear surfaces from metal to metal contact and thus improves the tribological properties.

If the reverse transformation of a shape memory alloy is arrested, a kinetic stop will appear in the next complete transformation. The kinetic stop temperature has a close relation with the previous arrest temperature. This kinetic stop can be regarded as a ‘‘memory’’ of the previous arrest temperature. This phenomenon is named temperature memory effect(TME). The TME induced by incomplete cycling in Ti-Ni-Nb and Ti-Ni-Cu alloys was systematically investigated by performing either a single incomplete cycle, or a sequence of incomplete cycles with different arrested temperatures. The results indicate that TME only exists in the heating process, and TME can occur both in B19′→B2 and B19→B2 reverse transformation during heating process. But, there is no evidence of TME during cooling in the Ti-Ni-X ternary alloys. And the reverse transformation temperature interval (A_f-A_s) of the Ti₄₄-Ni₄₇-Nb₉ alloy induced by TME can be significantly enlarged compared with that of the Ti-Ni-Cu alloy by performing multi-times incomplete transformation cycling with a decreasing order arrested temperature.

Two-layer structure thermal barrier coatings (TBCs) (NiCoCrAlY (bond coat)+(6%？8%, mass fraction) Y₂O₃-stabilized ZrO₂(YSZ top coat)) were deposited by electron beam physical vapor deposition (EB-PVD) on tube superalloy substrates. The samples were investigated by isothermal oxidation and thermal shock tests. It is found that the mass gains of the substrate with and without TBCs are 0.165 and 7.34 mg/cm², respectively. So the TBCs system is a suitable protection for the substrate. In thermal shock tests the vertical cracks initiate at the top coat and grow into the bond coat, causing the oxidation of the bond coat along the cracks. Failure of the TBCs system occurs by the spallation of the YSZ from the bond coat, and some micro-cracks are found at the location where the fragment of the YSZ top coat spalled from.

Al-Pb alloy was modified by high current pulsed electron beam and the microstructure, hardness and tribological characteristics were characterized by scanning electron microscopy, electronic microanalysis probe microanalysis, Knoop hardness indentation and pin-on-disc type wear testing machine. The results show that the microstructure and hardness can be greatly improved, and the modification layer consists of a molten zone, an overlapped zone of heat-affected and quasistatic thermal stress-affected zone and a transition zone followed by the substrate. The tribological properties of high current pulsed electron beam irradiated Al-Pb alloy are correspondingly improved largely. Optical observation and scanning electron microscopy analysis reveal that the low wear rate and lowest level in coefficient of friction at high load level for irradiated Al-Pb alloy are due to the formation of a lubricious tribolayer covering the worn surface, which is a mixture of Al₂O₃, Pb₃O₄ and silicate. The wear mode varies from oxidative wear at low load to film spalling at high load and, finally, adhesive wear.

The isothermal oxidation behaviors of the as-deposited NiAl coating on the nickel-based superalloy by electron beam physical vapour deposition(EB-PVD) and the NiAl coating after surface modifications of grinding and polishing were investigated. The as-deposited coating shows the least mass gain, the initially formed θ-Al₂O₃ scale spalls after only 1 h, and the succeeding scale formed is coarse and discontinuous and thus can not be used as protective coatings. Among the two surface-modified coatings, the ground coating results in the highest oxide growth rate, which is consistent with the SEM results where the scale spalls heavily and many voids appear between the scale and the NiAl coating. The scale spallation and void formation mechanisms during isothermal oxidation test of EB-PVD NiAl coating were also discussed.

The magnetization, magnetostriction and compressive strengths of arc-cast polycrystalline and directionally solidified Tb_0.36Dy_0.64(Fe_1？xMn_x)_1.9 (x=0, 0.05, 0.10, 0.15, 0.20) rods were investigated by VSM, standard strain gauge method and compressive tests, respectively. The results show that the magnetostriction λ_s, saturation magnetization M_s and magnetocrystalline anisotropy constant K₁ decrease with increasing the Mn concentration. The optical micrographs and XRD patterns show that the Tb_0.36Dy_0.64(Fe_1？xMn_x)_1.9 alloys are composed of MgCu₂-type Laves phase as matrix and a small amount of rare-earth rich phase. It is found that the distribution of the rare-earth rich phase has an important effect on mechanical property of Tb_0.36Dy_0.64(Fe_1-xMn_x)_1.9 samples. For the arc-cast samples, smaller equal-axial grains are arranged irregularly, which results in higher compressive strengths. However, the rare-earth rich phase is arranged as parallel arrays in the directionally solidified samples, which leads to smaller compressive strengths.

The oxidation behavior of NiTi and NiTiNb alloys containing different amounts of Nb (7%, 9%, mole fraction) were studied at 800 ℃ in air. It is found that the oxidation resistance of NiTi alloy can be effectively increased by the Nb addition. Under the same oxidation condition, the mass gain of NiTi is about 7 mg/cm², while the mass gains are only 3 mg/cm² for Ni₄₇Ti₄₄Nb₉ alloy and 2.4 mg/cm² for Ni₅₂Ti₄₁Nb₇. Moreover the oxidation resistance of single phase NiTiNb alloy is better than that of the dual-phase alloy with large amount of Nb precipitates. On the basis of thermodynamics and kinetics of oxidation, the effect of Nb alloying element on the oxidation behavior of NiTi-based alloys was discussed.

A high-current pulsed electron beam(HCPEB) generated on the system of Nadezhda-2 was applied to improve the microstructure and performance of 0.20% C low carbon steel. Surface layers of the samples bombarded by explosive electron beam at different pulses was observed by using electron microscopy. The physical model of the thermal-stress process and related modification mechanism as a result of HCPEB irradiation was also investigated. After HCPEB post treatments, obvious changes in microstructure and significant hardening occur in the depth of 200-250 μm from the surface after HCPEB irradiation. Rapid heating and subsequent rapid solidification induce heavy plastic deformation, which results in that the laminated structure of pearlite is substituted by dispersive rounded-like cementites in the near-surface. The effect of HCPEB treatment can reach more than 500 m depth from the surface. The original crystalline structure is changed to a different degree that grows with the numbers of bombardment, and in the surface layer amorphous states and nanocrystaline structures consisting of grains of γ-phase and cementite are found. The violent stress induced by HCPEB irradiation is the origin of the nanostructured and amorphous structure formation.

Aluminium nitride-silicon nitride-silicon carbide (AlN-Si₃N₄-SiC) composite ceramics were prepared to increase the bending strength and improve the phase structure of Si₃N₄-based ceramics. The ceramics were made by reactive sintering in N₂ atmosphere at 1 360 ℃, using Al as sintering additive. The phase composing of ceramics was identified with an X-ray diffractometer and the microstructure of the materials was studied by scanning electron microscopy. The results indicate that the phase structure is affected remarkably and the interface modality is changed. The interface between Si₃N₄ and SiC becomes blurry and that between SiC and AlN matches more better at the same time. But the liquid-phase appears during the reactive sintering along with the addition of Al by which the melting point of Si is decreased. The appearance of liquid Si decreases the bending strength of the ceramics. Lower temperature nitrification technic was introduced to avoid the appearance of liquid-phase Si. The optimum addition of Al was investigated by XRD and SEM analysis in order to obtain the maximal bending strength of materials.

Employing isothermal and isochronal differential scanning calorimetry, an analytical phase transformation model was used to study the kinetics of crystallization of amorphous Mg_82.3Cu_17.7 and Pd₄₀Cu₃₀P₂₀Ni₁₀ alloys. The analytical model comprised different combinations of various nucleation and growth mechanisms for a single transformation. Applying different combinations of nucleation and growth mechanisms, the nucleation and growth modes and the corresponding kinetic and thermodynamic parameters, have been determined. The influence of isothermal pre-annealing on subsequent isochronal crystallization kinetics with the increase of pre-annealing can be analyzed. The results show that the changes of the growth exponent, n, and the effective overall activation energy Q, occurring as function of the degree of transformation, do not necessarily imply a change of nucleation and growth mechanisms, i.e. such changes can occur while the transformation is isokinetic.

A boundary layer model was used to investigate the convection effects on phase and microstructure selection in directionally solidified peritectic alloy. Due to the convection effects, the steady-state compositions of one phase at interface corresponding to an initial composition reduce, which causes its steady-state point moves upward along its solidus line and the compositional range is not consistent with the band cycle in banding. A criterion of critical interface temperature was put forward to determine whether a phase entered steady-state growth or not. Furtherly by equivalent transformation, the equivalent solidus lines and subsequent equivalent phase diagram were derived for peritectic solidification with convection. Using this equivalent phase diagram, a phase and microstructure selection map is built for a peritectic alloy with convection effect, which shows that the compositional range for banding reduces, and moves to the hyperperitectic region, and also the coupled growth region of both solids comparing with purely-diffusive limit. The predicted map for directionally solidified Pb-Bi alloy agrees well with its experimental observations.

The structural, morphological, mechanical and tribological characterization of nanoscaled multilayer TiN/TaN coatings deposited by magnetron sputtering technology were investigated by low angle X-ray diffractometry, high angle X-ray diffractometry, atomic force microscopy, microhardness, pin-on-disc testing and 3-D surface profiler. The results show that the TiN/TaN coatings exhibit good modulation period and sharp interface between TiN and TaN layers. In mutilayered TiN/TaN coatings, TiN layers have cubic structure, but hexagonal structure emerged among TaN layers besides cubic structure as modulation period is beyond 8.5 nm. The microhardness is affected by modulation period and the maximum hardness value of 31.5 GPa appears at a modulation period of 8.5 nm. The coefficient of friction is high and the wear resistance is improved for TiN/TaN coatings compared with those of TiN coating; the wear mechanism exhibits predominantly ploughing, material transfer and localized spallation.

A surface treatment method was described, which can form a uniform and dense phosphate conversion coating on the die -casting magnesium alloy AZ91D in a non-chromate and non-nitrite bath. The coating consists of Zn₃(PO₄)₂？4H₂O, Zn, AlPO₄ and MgZn₂(PO₄)₂ analyzed by XRD. The SEM results show that the microstructure of the zinc phosphate coating transfers from flower-like to slab-like crystals with the increase of immersion time of magnesium alloy samples in the phosphating bath. The zinc phosphate coating formed in the bath with immersion time of 1 min is denser because metallic Zn and insoluble phosphate crystals co-deposit on the magnesium alloy surface and the growth of the crystals are restricted by each others. The zinc phosphate coating on the magnesium alloy is used as the base layer for further cataphoric and powder paintings. The cataphoric painting on AZ91D alloy based on phosphate coating has similar adhesion and corrosion-resistance to that based on the chromate conversion coating. But for powder painting, the former exhibits better adhesion property than the latter, due to the uneven microstructure and the enough thickness of the phosphate coating.

A bright electroless Ni-P deposition on AM50 magnesium alloy in a sulfate plating bath was proposed by using direct plating process with non-chromate pretreatment. The electroless Ni-P plating on AM50 magnesium alloy has an admirable appearance and good adhesion. The results indicate that the electroless Ni-P deposition with non-chromate pretreatment has better adhesion than that of zinc immersion coating. Anodic polarization curves indicate that the electroless Ni-P deposition obtained from the sulfate bath has similar corrosion-resistance to that obtained from basic nickel carbonate bath. The deposition process generates less pollutant by a non-chromate plating bath and is suitable for the magnesium alloys manufacture because of its low cost. The hardness of the electroless Ni-P plated AM50 is about HV 720.6 and HV 969.7 after heat treatments at 180 ℃ for 2 h. The wear resistance of Ni-P plated magnesium alloy specimens is about 5 to 9 times as high as that of bare magnesium alloys.

Composite metastable TiN and Ti_1？xAl_xN coatings with different Al content were deposited on 1Cr11Ni2W2MoV stainless steel for aero-engine compressor blades by arc ion plating. The results show that all coatings have a B1NaCl structure and the preferred orientation changes from (111) to (220) with increasing Al content; the lattice parameter of Ti_1？xAl_xN decreases with the increase of Al content. The oxidation-resistance of (Ti,Al)N coatings is significantly improved owing to the formation of Al-riched oxide on the surface of the coatings. The nitride coatings can significantly improve the corrosion-resistance of 1Cr11Ni2W2MoV stainless steel under the synergistic of water vapor and NaCl, and the corrosion-resistance becomes better when the Al content increases, because not only the quick formation of thin alumina layer prevents the further corrosion but also the formation of alumina seals the pinholes or defects in the coatings, which prevents the occurrence of localized nodules-like corrosion.

The chemical vapor(CVD) deposition-diffusion method was applied to prepare FeSi alloys with high silicon content up to 6.5%. In spite of various deposition and post-annealing, the sample remains α-Fe bcc structure. The cross section of the composition was analyzed to evaluate the Si content and distribution before and after annealing. The results show that the soft magnetic properties are improved by increasing the silicon content. For the samples containing about 6.5% Si, the coercivity decreases to 60 from 237.3 A/m of the original. It is also obtained that, in addition to the Si content, Si distribution has a large influence on the core loss due to the effect of resistivity. The micro-hardnesses were also evaluated along the cross-section after various annealings.

Hafnium carbide (HfC) was applied in space and aerospace due to its ultra high melting temperature, high specific strength and moderate oxidation resistance. A novel synthesizing method was used to produce low density and high strength HfC structural foams through the thermolysis and pyrolysis of Hf containing polymer precursors (mixing of hafnium trifluoroacetylacetonate and epoxy) under vacuum atmosphere. The X-ray diffraction analysis shows that the produced foam is primarily composed of HfC containing 9%？10% HfO₂. Several polymer powder compaction methods were used to improve the mechanical properties of HfC foam. Compression strengths of 200 MPa are achieved for HfC foams with density of 1.9 g/cm³ (total porosity about 85%). The proposed methodology of synthesizing HfC foam has the advantages of simple, inexpensive and less production time than alternate methods.

Niobium-silicide alloys have great potential for high temperature turbine applications. The two-phase Nb/Nb₅Si₃ in situ composites exhibit a good balance in mechanical properties. Using the 52 m drop tube, the effect of undercooling and rapid solidification on the solidification process and micro-structural characterization of Nb-Si eutectic alloy was studied. The microstructures of the Nb-Si composites were investigated by optics microscope (OM), X-ray diffraction (XRD) and scanning electron microscope (SEM) equipped with X-ray energy dispersive spectrometry (EDS). Up to 480 K, deep undercooling of the Nb-Si eutectic samples was successfully obtained, which corresponds to 25% of the liquidus temperature. Contrasting to the conventional microstructure usually found in the Nb-Si eutectic alloy, the microstructure of the undercooled sample is divided into the fine and coarse regions. The most commonly observed microstructure is Nb+Nb₅Si₃, and the Nb₃Si phase is not be found. The change of coarseness of microstructure is due to different cooling rates during and after recalescence. The large undercooling is sufficient to completely bypass the high temperature phase field.

The bonded NdFeB permanent magnet was painted by cathode electrophoretic technology. The effect of technological parameters on the thickness of the layer was researched. The optimum voltage, time, electrophoresis temperature, area-ratio and spacing between cathode and anode are 220-250 V, 2-3 min, 25-32 ℃, 7-10 cm and (2-4)∶1, respectively. After treated under optimum conditions, the excellent corrosion resistance of the bonded magnet is achieved, with temperature and humidity resistant time of 468 h, brine-fast resistant time of 48 h. The cathode electrophoretic technology and treating process were successfully applied to produce bonded magnets with mass capacity of tens of million pieces per year.

The preparation technology and magnetic properties of Nd_9.5Fe₇₇B₆Co₅Zr_2.5 nanocomposite magnets were investigated by melt spinning and crystallization process. The nonuniform composition and grain size can be induced by nanocomposite magnet prepared by arc-melt-spinning process, which will decrease the magnetic properties. These can be avoided by modification of preparing process. Induction-melt-spinning furnace was designed successfully and applied to prepare nanocomposite magnets. The bonded magnet with B_r=0.736, H_cb=418 kA/m, H_cj=630 kA/m, M_r/M_s=0.7 and (BH)_max=82.4 kJ/m³ was prepared by this technology.

A little amount of aluminum substituting for Ni was added to Ti₅₀Ni₄₈Fe₂ and Ti₅₀Ni_47.5Fe_2.5 alloys to improve the mechanical properties, especially the yield stress of the TiNiFe alloys. The martensitic transformation temperature and mechanical properties of Ti₅₀Ni_48-xFe₂Al_x and Ti₅₀Ni_47.5-xFe_2.5Al_x (x=0, 0.5, 1) alloys were examined, and it was revealed that 0.5% and 1%(mole fraction) aluminum addition lead to about 10℃ and 60？80 ℃ martensitic transformation temperature (M_S) decrease, respectively. 1%(mole fraction) aluminum addition enhances remarkably the yield stresses of Ti₅₀Ni₄₇Fe₂Al₁ and Ti₅₀Ni_46.5Fe_2.5Al₁ to 560 and 580 MPa, respectively. The systemic microstructure analysis indicates that the second phase Ti₂Ni at the grain boundaries plays an important role in improving the mechanical properties of TiNiFe shape memory alloys.

A 3-D simulation of grain growth was conducted by utilizing cellular automata (CA) and Monte Carlo (MC) algorithm. In the simulating procedure, the three-dimensional space is divided into a large number of 2-D isometric planes. Then, each of the planes is divided into identical square cells. Finally, the cellular automata and Monte Carlo algorithm are combined together to simulate the grain growth. Through an evolutionary simulation, the recrystallized microstructure, the grain growth rate and the grain size distribution are acceptably predicted. The simulation routine can be used to simulate the real physical-metallurgy processes and to predict quantitative dynamic information of the evolution of microstructure. Further more, the method is also useful for optimization of materials properties by controlling the microstructure evolution.

The powder mixture of Cu and graphite was mechanically alloyed (MA) in an oscillating type ball mill. The milling time was varied in order to investigate its influence on the microstructural evolution of mechanically alloyed powders. The phase constituent, alloying characteristics, grain size and lattice distortion of these powders were determined by X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy and transmission electron microscopy. The results show that the C is confirmed to dissolve in the Cu lattice, forming solid solution of carbon in copper the lattice parameter of copper increases with carbon concentration increasing, up to a saturation value of about 4%C(mass fraction). Higher ball-mill energy is beneficial for twins and nanograin formation.

Three kinds of Ni and Al powder mixtures with nominal composition Ni75Al25 were employed to prepare Ni₃Al alloys by spark plasma sintering(SPS) process. The raw powders include fine powder, coarse powder and mechanically-alloyed fine powder. The effects of powder characteristics and mechanical alloying on structure and properties of sintered body were investigated by scanning electron microscopy(SEM), X-ray diffraction(XRD), bending test and Vickers hardness measurements. For all mixture powders near fully dense Ni₃Al alloys (relative density＞99.5%) are obtained after sintering at 1 150 ℃ for 5 min under 40 MPa. However a small fraction of Ni can be reserved for alloy from coarse powders. The results reveal that grain size is correlated with particle character of raw powder. Ni₃Al alloy made from mechanically-alloyed fine powder has finer and more homogenous microstructure. The hardness of all alloys is similar varying from HV470 to 490. Ni₃Al alloy made from mechanically-alloyed fine powder exhibites higher bending strength (1 070 MPa) than others.

Mold filling in lately-developed Thixomolding^？ process is a complex process, of which numerical simulation is necessary for development. Governing equations and numerical models are first given, and then the experiment and its filling simulation are carried out. The results demonstrate that the modeling temperature changes from 864 to 873 K when the barrel temperature is 873 K. The difference is primarily in the runner system, but nearly invariable in the part. Consequently, the slurry fills the cavity smoothly with low solid fraction, and the filling process finishes in 5 ms, the filling process completes successfully before solidification of the slurry, which has good agreement with the experiment. Through a snapshot of the filling process and defects tracking, drawbacks are displayed and confirmed in the experiment.

The creep behavior of directionally solidified (DS) superalloy IC10 was investigated under 192 MPa and 218 MPa at 980 ℃. Under the testing conditions, the marked creep characteristic of the superalloy is that the creep curve has a short primary and secondary stage and a long tertiary stage. Another creep characteristic is that the superalloy has excellent plasticity at high temperature. To study the creep behavior, the microstructure was observed by SEM and TEM. Different from other microstructure of Ni-base superalloys, superalloy IC10 forms incompletely rafted γ' phase during the creep processes. To understand the creep deformation mechanism of superalloy IC10, the movement of dislocations was analyzed. The results show that the dislocations moving in the γ matrix and climbing over the γ' precipitates is the main deformation mechanism under the experimental conditions.

The electrical properties of La_0.6Sr_0.4Co_1-yFe_yO₃ (LSCF, y=0？1.0) cathode materials were measured by DC four probes, X-ray photo-electron spectrum (XPS) was also introduced to determine the chemical state of Co, Fe ions in LSCF. It is found that the electrical conductivity of each sample has a maximum value with increasing temperature. XPS analysis shows that Co ion has three different chemical states, corresponding to two with Fe ion. The analyses indicates that the small-polaron hopping mechanism dominates the electron conduction at low temperature, while at high temperature, the three factors such as the thermally activated disproportionation of Co³⁺ ions into Co²⁺ and Co⁴⁺ pairs, the ionic compensation of oxygen vacancies formed at high temperatures, and Fe⁴⁺ ions charge compensation preferential to Co⁴⁺, all contribute to electrical conduction.

The effect of Nb in (La_0.5Ce_0.5)_64？xAl₁₆Ni₅Cu₁₅Nb_x (x=0-5, mole fraction) bulk metallic glasses was investigated by X-ray diffractometry, differential scanning calorimetry, and scanning electron microscopy. Fully amorphous rods up to 5 mm in diameter were obtained using copper mold. Their lower glass transition temperatures are of about 401？407 K and wide supercooled liquid regions are up to 75 K. The oxidation resistance of the LaCe-based glassy alloys can be largely enhanced by adding tiny Nb, which makes the developed LaCe-based bulk metallic glasses more attractive for potential industrial applications.

The microstructures of mechanical alloyed(MA) Ti-12%Mg alloy powders were examined using a high resolution TEM (HRTEM). The effect of MA atmospheres such as argon gas and liquid isopropyl alcohol on the resultant microstructure was investigated. Both the MA powders form a homogeneous Ti-Mg solid solution, but the oxidation behavior is distinguished. The phase change was studied as a function of milling conditions and annealing temperatures.

Based on the heat transfer theory and liquid solidification theory, the heat transfer during the rapid solidification process of amorphous ribbons prepared by melt spinning was approximately modeled by one-dimensional heat conduction equation. Besides, integration with the temperature gradient, the relationship between the ribbon thickness and solidification time was derived according to the boundary conditions of ribbon-copper wheel. A simply theoretical model was obtained to calculate the cooling rates of aluminum amorphous ribbons. According to the above theoretical model, the critical cooling rate of aluminum amorphous ribbons by melt spinning is above 10⁶ K/s, which proves that the aluminum based alloys belong to the marginal glass forming ability of alloys. The calculated results are in good agreement with other estimated values reported previously.

The effect of coupling with calculation of phase diagrams on microsegregation forming simulation was investigated. The traditional simplified phase diagram and calculated phase diagram were introduced into the numerical models respectively and simulation on microsegregation forming of the Al-4.5%Cu alloy ingot was also presented. The simulation results were both compared with the experiment results. The results show that the calculated sencondary arm spacing with these two kinds of phase diagram are almost the same because relationship between the coarsening model and the information of phase diagram is not close. The calculated eutectic phase volume fractions of different locations in the ingot coupled with different phase diagrams are discrepant. The calculated volume fractions are consistent with the experiment results when calculated phase diagram couples, but are far from the experiment results and obviously inacceptable when traditional simplified phase diagram couples. So, coupling with accurate calculated phase diagrams is very significant for microsegregation forming simulation since much information of the phase diagram is used in the models and it can improve the precision of simulation results.

The experiments of continuous and directional solidification of titanium alloys with cold crucible were carried out in a multifunctional electromagnetic cold crucible apparatus. Parameters and factors influencing the surface crack and macrostructure of titanium alloy ingots were studied. The mechanism of the parameters and factors influencing the surface crack and macrostructure of the ingots were interpreted. The results show that the surface cracks of the prepared ingots decrease with the increase of the input power from 50 to 60 kW or with the increase of the coil turns from 3 to 5 circles. The surface cracks increase with the increase of withdrawal velocity from 3 to 5 mm/min or the height of the primer from 2 to 3 cm, then decrease with the increase of withdrawal velocity from 5 to 8.7 mm/min or the height of the primer from 3 to 4 cm. Coil turns is the most important one in all parameters effect on the surface crack, the input power is more important, then the withdrawal velocity is important and the height of the primer is the least important. Withdrawal velocity is the most important factor affecting the macrostructure, and effects of other factors on macrostructure is slight. With the decrease of velocity from 8.7 to 0.5 mm/min, the quantity of grains reduces, the grain orientation degree becomes small, and the solidification fronts change from concave to plane to convex. The ingot can be directional solidified at velocity of 1 mm/min. The ingot with free surface crack and directional macrostructure is prepared under definite conditions.

Pure copper (99.95%) square bars (32 mm×32 mm) were subjected to equal channel angular pressings (ECAP) for 4 passes at room temperature, using 90？ die by route C. Optical microscopy (OM) was used to examine microstructure evolution. Small tensile specimens were sectioned by wire cutting and the mechanical properties were tested at room temperature and under the as-processed condition. The results show that significant inhomogeneity and anisotropy of microstructure and mechanical properties exist in the ECAPed material. The nearer the sample to the surface, the more inhomogeneous the microstructure is. In mechanical properties, inhomogeneity and anisotropy are ECAP pass dependent. With the higher accumulated strain resulted from high ECAP passes, the inhomogeneity and anisotropy decrease. The inhomogeneity and anisotropy can be considered to be resulted from the distributions of the strain inhomogeneity.

A new kind of amorphous active brazing alloy foil with the composition of Ti40Zr25Ni15Cu20 was successfully synthesized using melt spinning in roll forging machine in argon atmosphere. The amorphous structure and composition were examined by X-ray diffraction, differential thermal analysis and energy dispersive X-ray detector. The results show that the Ti40Zr25Ni15Cu20 amorphous alloy foil has excellent wettability on Si₃N₄ ceramic and demonstrate a strong glass forming ability. The reduced glass transition temperature (T_rg) and the temperature interval of supercooled liquid region before crystallization are 0.76 and 78 K, respectively.

The thermal stability of Al₃(Sc,Zr) precipitates in the cold worked Al-Mg-Sc-Zr alloy after elevated temperature exposure was investigated. The evaluation was conducted using room temperature tensile, Vicker’s hardness, optical metallography and scanning electron microscope (SEM) with the backscatter. The results show that the Al₃(Sc,Zr) precipitates and mechanical properties have no obvious change, and the grains keep elongated along the working direction as that in cold worked sample after exposure at 300 ℃ for 1 000 h. The coarsening of Al₃(Sc,Zr) precipitates occurs and is no longer effective on the recrystallization resistance, and partial recrystallization is observed after 400 ℃ exposure. In particular, after 500 ℃ exposure, the hardness decreases drastically and the alloy has fully recrystallized due to the obvious coarsening of Al₃(Sc,Zr) precipitates.

A modified cellular automaton (MCA) model has been extended to the ternary alloy system by coupling thermodynamic and phase equilibrium calculation engine PanEngine. In the present model the dendrite growth is driven by the difference between the local equilibrium liquidus temperature and local actual temperature, incorporating the effect of curvature. The local equilibrium liquidus temperature is calculated with PanEngine according to the local liquid concentrations of two solutes, which are determined by numerically solving the species transport equation in the domain. Model validation was carried out through the comparison of the simulated values to the prediction of the Scheil model for solute profiles in the primary dendrites. The simulated data with zero solid diffusivity and limited liquid diffusivity were increasingly close to the Scheil profiles as the solidification rate decreased. The simulated microstructure and microsegregation in an Al-Cu-Mg ternary alloy were compared with those obtained experimentally.

In order to examine the dependences of tensile properties of a forged Mg-13Li-X alloy on hot-rolling deformation and the underlying mechanisms tensile tests, residual stress measurements and texture analyses were conducted in the present study. It is found that after a hot-rolling deformation of 50% at 200 ℃, no much changes in tensile properties, nature and magnitude of residual stresses, and texture type and intensity can be identified for the alloy investigated. The insensitivity of tensile properties of the Mg-Li-X alloy to hot-rolling deformation is attributed at least partially to the insensitivity of residual stress and texture to hot-rolling.

The effects of different processing techniques on the microstructure and compressive properties of NiAl–28Cr-5.5Mo-0.5Hf alloys were evaluated. These processing routes can all improve the compressive properties of NiAl–28Cr-5.5Mo-0.5Hf alloys. The microstructural refinement and the stronger precipitation strengthening mechanisms are responsible to the improvement of the compressive properties under the condition of higher undercooling degree. In addition, high magnetic field treatment and trace rare earth elements addition can significantly optimize the mechanical properties of NiAl-28Cr-5.5Mo-0.5Hf alloy. The improvement of NiAl-28Cr-5.5Mo-0.5Hf alloy seems to be realized by a complicated combination of different processing route. A directional solidification at a high drawing rate under high magnetic field for NiAl-28Cr-5.5Mo-0.5Hf alloy containing minor rare earth element is a desirable route to the high performance NiAl-28Cr-5.5Mo-0.5Hf alloy.

The microstructures of the AZ91D die-cast magnesium alloy were investigated by scanning electron microscopy (SEM), X-ray diffractometry (XRD) and energy dispersion spectroscopy (EDS). Moreover, the microstructure change of AZ91D samples was observed during the process of heat treatment at 300 ℃ for different time. And the tensile testing was carried out for these samples and the fracture morphology of the tensile test samples was also examined. The results show that the microstructures of AZ91D magnesium alloy are mainly composed of α-Mg phase and β-Mg₁₇Al₁₂ phase. The morphology of the β phase alters from continuous distribution to discontinuous distribution during the process of heat-treatment. Meanwhile, the ductility of the materials reduces from 1.71% to 1.08% after a long time heat-treated at 300 ℃. Moreover, the quasi-cleavage fractures characters are also found in the fracture morphology. The granulation and discontinuous distribution of β-Mg₁₇Al₁₂ results in the deterioration of the ductility of AZ91D die cast magnesium alloy.