Quantitative characterization of β-solidifying γ-TiAl alloy with duplex structure  

双态组织β凝固型γ-TiAl合金的定量表征

作　　者：Run-run XU Miao-quan LI 胥润润;李淼泉(西北工业大学材料学院,西安710072)

机构地区：[1]School of Materials Science and Engineering,Northwestern Polytechnical University,Xi’an 710072,China

出　　处：《Transactions of Nonferrous Metals Society of China》2021年第7期1993-2004,共12页中国有色金属学报（英文版）

基　　金：the financial supports from the National Natural Science Foundation of China(No.51975478);the Fundamental Research Funds for the Central Universities,China(No.3102019MS0403).

摘　　要：For precise plastic deformation,microstructure control is essential especially for β-solidifying γ-TiAl alloy with duplex structure.Based on stereology,the microstructure of isothermally compressed γ-TiAl alloy was divided into β_(0) grains,remnant α_(2)/γ lamellar colonies,α_(2) and γ grains.The results show that the volume fraction of β_(0) grains slightly increases in the isothermally compressed γ-TiAl alloy with the increase of height reduction.Meanwhile,the volume fractions of remnant α_(2)/γ lamellar colonies and α_(2) grains decrease.However,the volume fraction of γ grains increases from 64.39% to 78.47%.According to the quantitative results,the α→γ phase transformation was investigated in-depth,and it is found that isothermal compression accelerates the α→γ phase transformation.The first α→γ phase transformation is similar to ledge-controlled transformation,through which remnant α_(2)/γ lamellar colonies finally convert intoγgrains in isothermal compression.The second is achieved by α/γ phase interface immigration.显微组织调控对于金属材料的精确塑性成形极为必要,尤其是双态组织γ-TiAl合金。基于体视学原理,双态组织γ-TiAl合金高温塑性变形后的显微组织分为β_(0)晶粒、残余α_(2)/γ片层团、α_(2)晶粒和γ晶粒4类结构单元。结果表明:随着变形程度的增大,γ-TiAl合金高温塑性变形后β_(0)晶粒的体积分数略微增大,残余α_(2)/γ片层团和α_(2)晶粒的体积分数逐渐减小,而γ晶粒的体积分数逐渐从64.39%增大至78.47%。基于定量结果,深入研究α→γ相变,证实高温塑性变形促进α→γ相变。第一种α→γ相变类似于台阶控制生长机制,残余α_(2)/γ片层团通过该种机制逐渐转变为γ晶粒;第二种α→γ相变为α/γ相界面迁移机制。

关 键 词：TiAl alloy STEREOLOGY digital image analysis MICROSTRUCTURE phase transformation 

分 类 号：TG146.23[一般工业技术—材料科学与工程]