温度对γ-TiAl合金棒材拉伸性能与断裂机制的影响

Effect of Temperature on Tensile Properties and Fracture Mechanism ofγ-TiAl Alloy Bars

本工作采用包套热挤压工艺制备了Ti-44Al-3Ta-0.3(Cr,W)(at%)棒材,测试了室温~800℃的拉伸性能,通过SEM、XRD、TEM等实验方法研究了棒材挤压态和热处理组织的断裂行为。结果表明,合金的2种组织的屈服强度都随拉伸温度的提高而降低,400~600℃的峰值应力值则随着温度的升高而提高,挤压组织的极限应变值整体略高于热处理的极限应变值。合金的脆性-韧性转变(BDT)温度在800℃附近。挤压态组织的断裂主要由穿层和沿层的混合断裂模式控制,断口表面还存在二次裂纹。拉伸温度对2种组织内的晶团尺寸、片层厚度、孪晶以及相变均有影响。

Ti-44Al-3Ta-0.3(Cr,W)(at%)bars were prepared by the hot canned extrusion.The as-extruded(AE)and heat-treated(HT)microstructures,the tensile properties and fracture morphologies of the bars were investigated by SEM,XRD,TEM.The results show that the yield strength of the two kinds of microstructures decreases with the increase of the tensile temperature,and the peak stress value increases with the increase of the temperature from 400℃to 600℃.The ultimate strain value of the as-extruded microstructure is slightly higher than that of the heat treated microstructure.The brittle-toughness transition(BDT)temperature of the alloy is around 800℃.The room temperature fracture of the extruded microstructure is mainly controlled by the mixed fracture modes of inter-lamellar and trans-lamellar fracture,and there are secondary cracks on the fracture surface.The tensile temperature has affected the size,the lamellar thickness,the twins and phase transformation in the two kinds of the microstructures.