运用Gleeble-1500D型动态热模拟试验机对Ti-47Al-2Nb-2Cr(摩尔分数,％)合金在温度为950～1150℃、应变速率为0.001～1 s-1进行热模拟压缩试验,通过对变形开裂后试样断口裂纹形貌的分析,阐明TiAl合金高温变形过程的开裂损伤机理.结果表明:在低温(<1000℃)、高应变速率(>0.1 s-1)条件下,TiAl合金高温变形开裂方式为沿45°剪切开裂,随着变形温度的升高和应变速率的降低,材料发生纵向自由表面开裂.采用二分法确定TiAl合金不同温度和应变速率下的临界变形量,引入考虑温度和应变速度参量的Zener-Hollomon因子,构建TiAl合金高温变形过程临界损伤模型.%The hot deformation behaviors of Ti-47Al-2Nb-2Cr (mole fraction, ％) alloys were studied by Gleeble-1500D at the temperature range of 950-1150 ℃ and strain rate of 0.001-1 s-1. By true stress-strain curve analysis, fracture thermomechanical simulator appearance analysis, the results indicate that shear cracking along the direction of 45° with respect to the compression axis occurs at lower temperature (<1000 ℃) and higher strain rate (>0.1 s-1), then it is attributed free surface cracking along longitude with increasing deformation temperature and decreasing strain rate. The critical strain is obtained by bisection method at various temperature and strain rates. The Zener-Hollomon parameter, which considers the effect of temperatures and strain rate, is employed to establish the correlation among critical strain and hot processing parameters in the present investigation. Finally, a fracture criterion of Ti-47Al-2Nb-2Cr alloy during hot deformation is successfully developed and verified by experiment.
展开▼
