Effects of Large Deformation Near-isothermal Forging on Microstructures and Properties of TiAl Alloy
SI Jia-yong1, LI Sheng2, ZHANG Ji2
1. College of Mechanical & Electrical Engineering,Central South University of Forestry & Technology,Changsha 410004,China;
2. High Temperature Material Research Institute,Central Iron & Steel Research Institute,Beijing 100081,China
Abstract：The effects of increasing deformation strain on the microstructure uniformity and mechanical property stability of Ti-46.5Al-2.5V-1.0Cr-0.3Ni alloy were quantitative studied by single near-isothermal forging. The observed microstructure and measured hardness and strength can revealing the basic relationship among deformation strain, macrostructure and microstructure. The results show that distribution of flow lines is more uniform and the area of uniform zone is enlarged with the engineering strain raised from 65%, 70%, 75%, 80% to 85%. In the forged pancake, the proportion of uniform zone expand to 68.0％ when the strain is 85%. And the deformation microstructure is composed by equiaxed γ,α2 and a few remnant laminas. The grain dimension is obviously refined and the vast majority is equiaxial microstructure. The hardness testing shows that hardness of uniform zone is tending to be uniformity and the average hardness is continuous to increase. The room temperature compression samples were machined from stagnant zone and uniform zone with heat treatment at 1250℃/15h/AC. The dispersity of room temperature compression results is reduced and it means that property stability is improved with the increased engineering strain.
司家勇, 李胜, 张继. 大变形量近等温锻造开坯对TiAl合金组织与性能的影响[J]. 材料工程, 2013, 0(6): 40-44.
SI Jia-yong, LI Sheng, ZHANG Ji. Effects of Large Deformation Near-isothermal Forging on Microstructures and Properties of TiAl Alloy. Journal of Materials Engineering, 2013, 0(6): 40-44.
 SEMIATIN S L. Wrought processing of ingot-metallurgy gamma titanium aluminide alloys. Gamma Titanium Aluminides. Warrendale: TMS, 1995. 509-524. YAMAGUCHI M, INUI H, ITO K. High-temperature structural intermetallics[J].Acta Metall Mater,2000,48(1):307-322. SEMIATIN S L, SEETHARAMAN V, JAIN V K. Microstructure development during conventional and isothermal hot forging of a near-gamma titanium aluminide[J]. Metall & Mater Trans A,1994, 25A(12): 2753-2768. FUJIWARA T, NAKAMURA A, HOSOMI M, et al. Deformation of polysynthetically twinned crystals of TiAl with a nearly-stoichiometric composition[J]. Philosophical Magazine A, 1990, 61(4): 591-606. 张永刚,韩雅芳,陈国良,等. 金属间化合物结构材料[M]. 北京:国防工业出版社,2003. SI Jia-yong, HAN Peng-biao, ZHANG Ji. The design for the isothermal forging of Ti-46.5Al-2.5V-1.0Cr-0.3Ni alloy[J]. Journal of Iron and Steel Research International, 2010, 17(8): 67-73. SEMIATIN S L, CHESNUTT J C, AUSTIN C, et al. Processing of intermetallic alloys. Structural Intermetallics. Warrendale: TMS, 1997. 263-276. SEETHARAMAN V, SEMIATIN S L. Plastic-flow and microstructure evolution during hot deformation of a gamma titanium aluminide alloy[J]. Metall & Mater Trans A, 1997, 28A (11): 2309-2321. 司家勇,高帆,张继. 变形方向对TiAl合金二次热变形行为的影响[J]. 材料工程, 2010,(12): 51-54.SI Jia-yong,GAO Fan,ZHANG Ji.Effect of direction on flow behavior of TiAl alloy in secondary hot deformation[J].Journal of Materials Engineering,2010,(12):51-54. 汪大年. 金属塑形成形原理[M]. 北京:机械工业出版社,1982. KIM Y W. Strength and ductility in TiAl alloys [J]. Intermetallics,1998, 6(7): 623-628. SEMIATIN S L, SEETHARAMAN V, WEISS I. Hot working of titanium alloys-an overview. WEISS I E, SRINIVASAN R,BANIA P J,et al.Advances in the Science and Technology of Titanium Alloy Processing.Warrendale:TMS,1997.3-73.