Correlation between liquid structure and
γ2-phase precipitation
of Cu-Al-Ni shape memory alloys
γ2-phase precipitation
of Cu-Al-Ni shape memory alloys
(Key Laboratory of Liquid Structure and Heredity of Materials,
Ministry of Education,Shandong University, Ji′nan 250061, China)
Ministry of Education,Shandong University, Ji′nan 250061, China)
Abstract: Cu71Al25Ni4 (mole fraction,%) shape memory alloy ribbons exhibit a good shape memory effect, which were prepared by melt-spinning technique. The microstructure of the as-spun ribbons was identified by D/Max-rA X-ray diffractometer. The order degree of martensite increases with decreasing liquid quenching temperature at the same quenching rate. The liquid structure of Cu75Al25 and Cu71Al25Ni4 was investigated using X-ray diffraction method. The distinct pre-peaks have been found in front of main peaks of the structure factors. The pre-peak increases intensity with decreasing temperature or adding Ni. Gaussian peaks decomposing radial distribution function (RDF) indicated that Cu-Al distance is anomalously short. These results suggest that a strong interaction between Cu and Al is favorable to form β-phase-like clusters, which leads to chemical medium-range ordering in melt. This promotes formation of order martensite and suppresses γ2-phase precipitation.
Key words: CuAlNi alloy; liquid structure; shape memory alloy; X-ray diffraction