TC6钛合金高温准静态与室温动态变形条件下微结构演化对比

Comparative Studies on Microstructure Evolution of TC6 Titanium Alloy Deformed under the Condition of High Temperature Quasistatic State and High Strain-Rate

摘要:

采用gleeble-1500热模拟试验机及分离式霍普金森压杆技术，对TC6钛合金试样进行高温准静态(0.01 s-1)压缩试验及室温高应变率(103 s-1)剪切试验，通过光学显微镜及透射电镜对比研究2种变形条件下材料微结构演化特点。结果表明：在2种变形条件下材料微结构演化显著不同。在高温准静态条件下变形时，TC6钛合金微结构演化经历了4个阶段：等轴状α相变形为板条状→板条状α相断裂，同时出现动态再结晶晶粒→动态再结晶晶粒长大→发生α/β相变；在高应变率加载条件下变形时，TC6钛合金微结构演化经历了3个阶段：等轴状α相变形为板条状→位错的快速运动，板条状α相变形为更为细长狭窄的长条状→长条状α相断裂，同时出现少量动态再结晶晶粒；在2种变形条件下，TC6钛合金均发生了动态再结晶，但高温准静态下，动态再结晶晶粒较多且发生长大，尺寸为3~5 μm，而高应变率加载条件下形成的动态再结晶晶粒较少且没有长大，尺寸为0.1~0.2 μm

Abstract:

An high temperature quasistatic compression test (0.01 s-1) and a dynamic shearing experiment (103 s-1) on TC6 titanium alloy were performed by the gleeble-1500-type thermal simulation testing machine and a split Hopkinson bar process, respectively. Microstructure evolution of TC6 titanium alloy deformed under the condition of high temperature and high strain rate were contrastively investigated by means of optical microscope and transmission electron microscopy. Results show that the microstructure evolution of TC6 titanium alloy deformed at high temperatures is observably different from that at high strain-rate. The former includes four stages, i.e. deforming of equiaxed-type α phase to lath-shape α phase, breakdown of lath-shape α phase and simultaneous appearing and growth of dynamically recrystallized grains and phase transformation of α/β. The later goes through three stages, i.e. deforming of equiaxed-type α phase to lath-shape α phase, and then to lathy α phase due to rapid movement of dislocation, breakdown of lathy α phase and appearing of a few dynamically recrystallized grains. Under the two conditions of deforming, there is dynamically recrystallized grains occurring without exception, but there is a greater amount of dynamically recrystallized grains under the condition of high temperature and the dynamically recrystallized grains have grown up with sizes of 3-5 μm approximately. Whenas there are a few dynamically recrystallized grains that never grow up at high strain-rate with sizes of 0.1-0.2 μm approximately