TA15钛合金β热变形行为及显微组织

Hot Deformation Behavior and Microstructure of TA15 Titanium Alloy inβ Field

基于二元相图计算法和差示扫描量热法(DSC)精确测定了TA15钛合金的相变点。采用热模拟压缩实验、光学显微镜(OM)及电子背散射衍射技术(EBSD)和定量分析法研究了TA15钛合金的β热变形行为,分析了变形温度、应变速率和变形量对其流变应力和显微组织的影响规律。结果表明:TA15钛合金在β热变形时,流变应力曲线呈现两种软化态势:高应变速率条件下,流变应力曲线呈现动态再结晶型,而低应变速率条件下流变应力曲线呈现动态回复型;低应变速率下获得极细的片状马氏体微结构,而高应变速率下为粗大的板状马氏体微结构,且大角度晶界比例较低;应变速率对显微组织特征参数(β晶粒大小及不均匀性、β转变组织片层厚度以及长宽比)的影响较为显著。研究结果可为优化TA15钛合金β热变形工艺参数,获得良好的组织形态提供理论依据。

The phase transition point of TA15 titanium alloy was detected accurately by differential scanning calorimetry （DSC） method and calculation method based on the binary phase diagram. Hot deformation behavior in β field of TA15 titanium alloy was studied by thermal simulation compression experiment, optical microscope （OM） , electron backseattered diffraction （EBSD） technolo- gy and quantitative analysis. Then the effects of deformation temperature, strain rate and deformation degree on flow stress and micro- structure were analyzed. The results showed that the flow stress curves of TA15 titanium alloy through β filed hot deformation showed two kinds of softening style. The flow stress curves under high strain rate were dynamic recrystallization style, while those under low strain rate showed dynamic recovery curve style. Thin plate martensite microstrueture was obtained through β thermal deformation at low strain rate and thick lath martensite microstructure with low proportion of large-angle grain boundaries was gained under high strain rate conditions. The influences of strain rate on microstructure characteristic parameters （ β grain size and heterogeneity, average thickness and aspect ratio of β transformed lamellar microstructure） were significant. The results provided a theoretical basis for the optimization of β hot deformation process of TA15 titanium alloy to get fine microstructure.