利用Gleeble-3500型热模拟试验机,对铝质量分数分别为8%,10%,12%的三种铁-锰-铝-碳系低密度钢进行了不同变形温度(950~1150℃)及应变速率(0.01~1.0 s-1)下的压缩试验,研究了该低密度钢在高温下的塑性变形行为并观察了压缩变形前后的显微组织.结果表明:在950~1150℃,应变速率0.01~1.0 s-1下变形时,三种试验钢的流变应力对温度和应变速率均较敏感,流变应力随着应变速率的增加及变形温度的降低而提高;变形后,铝质量分数为12%的试验钢组织中铁素体呈带状,不连续地分布于奥氏体基体中;在相同应变速率下,其奥氏体与铁素体晶粒随着变形温度的升高逐渐长大,相同温度较高应变速率下的奥氏体与铁素体晶粒较细小;铝质量分数为12%试验钢的动态再结晶热变形激活能为592.437 kJ·mol-1,其Zener-Hollomon参数方程为Z=ε·exp(592.437/RT).
The compression experiments of three Fe-Mn-Al-C low density steels with aluminum content of 8wt%,10wt% and 12wt% were conducted by Gleeble-3500 hot simulator at different deformation temperatures from 950 ℃ to 1150 ℃ and different strain rates from 0.01 s-1 to 1.0 s-1 .The hot deformation behaviors of this low density steels were studied at high temperatures and the microstructures before and after compression were observed.The results show that during deformation at the temperatures from 950 ℃ to 1150 ℃ and strain rates from 0.01 s-1 to 1.0 s-1 ,the flow stresses of three tested steels were all sensitive to the temperatures and strain rates and increased with the increase of strain rate and with the decrease of the deformation temperature.After deformation,the ferrite in the microstructure of the tested steel with 12wt% aluminum was belt-like and distributed discontinuously in austenite matrix.The grains of ferrite and austenite grown larger and larger with the temperature rising at the same strain rate and were relatively fine at a relative high strain rate at the same temperature.The apparent activation energy of the tested steel with 12wt% aluminum was 592.437 kJ·mol-1 and the Zener-Hollomon parameter equation was listed as Z =ε·exp(592.437/RT).
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