微细晶γ-TiAl合金的显微组织分析

Analysis on microstructure of γ-TiAl alloy with ultra-fine grain

采用粉末高能球磨及放电等离子烧结方法获得TiH2-47Al-0.2Si-5Nb和TiH2-47Al-0.2Si-7Nb两种微细晶合金。借助X射线衍射仪、扫描电子显微镜及透射电子显微镜对两种合金的球磨粉末颗粒及烧结组织形貌、晶粒大小、微观应力等进行分析。结果表明,经24 h高能球磨的两种粉末颗粒均达到纳米尺度,晶粒微变应变值分别为1.296%和1.536%。球磨粉末经1000℃放电等离子烧结后的显微组织由等轴状的TiAl相及弥散分布的颗粒状Ti3Al相组成,晶粒尺寸大部分低于500 nm,在晶界及晶内分布着大量的位错线及位错网。

Two alloys of TiH2-47Al-0.2Si-5Nb and TiH2-47Al-0.2Si-7Nb with ultra-fine grain were obtained by high energy ball milling and spark plasma sintering .The morphology , grain size and micro-strain of milled powder and its sintered microstructure were investigated by XRD, SEM, and TEM.The results show that after high energy ball milling for 24 h, two kinds of milled powder are reduced to nanoscale and microeconomics strain are increased to 1.296% and 1.536%, respectively.The microstructure is composed of equal axial TiAl and disperse granular Ti 3 Al, and most of the grains size are less than 500 nm after spark plasma sintering at 1000 ℃.A large number of dislocation lines and networks are distributed in the grain boundary and inner crystal .