Microstructure and tensile properties of
containerless near-isothermally forged TiAl alloys
containerless near-isothermally forged TiAl alloys
(1. State Key Laboratory for Porous Metals Materials, Northwest Institute for Nonferrous Metal Research,
Xi’an 710016, China;
2. State Key Laboratory of Powder Metallurgy, Central South University, Changsha 410083, China)
Xi’an 710016, China;
2. State Key Laboratory of Powder Metallurgy, Central South University, Changsha 410083, China)
Abstract: Ti−47Al−2Nb−2Cr−0.4(W, Mo) (mole fraction, %) alloy ingot fabricated using vacuum consumable melting was containerless near-isothermally forged, and the high temperature forgeability, microstructure and tensile properties were investigated. The results show that the TiAl ingot exhibits good heat workability during containerless near-isothermally forging process, and there are not evident cracks on the surface of as-forged TiAl pancake with a total deformation degree of 60%. The microstructure of the TiAl ingot appears to be typical nearly-lamellar(NL), comprising a great amount of lamellar colonies (α2+γ) and a few equiaxed γ grains. After near-isothermally forging, the as-forged pancake shows primarily fine equiaxed γ grains with an average grain size of 20 μm and some broken lamellar pieces, and some bent lamellas still exist in the hard-deformation zone. Tensile tests at room temperature show that ultimate tensile strength increases from 433 MPa to 573 MPa after forging due to grain refinement effect.
Key words: TiAl alloy; microstructure; tensile property; containerless near-isothermal forging; grain refinement