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利用Gleeble-3500热模拟试验机进行双道次压缩试验,研究了Ti对700 MPa级高强度汽车大梁钢静态软化行为的影响。通过测量不同温度和不同道次间隔时间的“应力-应变”曲线,计算出了相同条件下无Ti钢和含Ti钢的再结晶体积分数。结果表明,Ti的添加不仅可以在高温下阻碍等轴晶粒的长大,而且能够抑制形变奥氏体的静态再结晶行为,降低静态软化率。添加0.04%Ti后,静态再结晶激活能由260 kJ·mol~(-1)提高至321 kJ·mol~(-1)。静态再结晶激活能的提高归因于含Ti钢中形成的(Ti,Nb)(C,N)等析出相在高温度下对晶界迁移的阻碍。
The double-pass compression test was carried out on a Gleeble-3500 thermal simulator to study the effect of Ti on the static softening behavior of 700 MPa high-strength automotive steel. The recrystallization volume fraction of Ti-free steel and Ti-containing steel under the same conditions was calculated by measuring the “stress-strain” curve for different temperatures and intervals between passes. The results show that the addition of Ti can not only block the growth of equiaxed grains at high temperature, but also restrain the static recrystallization of deformed austenite and decrease the static softening rate. After addition of 0.04% Ti, the static recrystallization activation energy increased from 260 kJ · mol -1 to 321 kJ · mol -1. The increase of static recrystallization activation energy is attributed to the obstruction to the grain boundary migration of precipitates (Ti, Nb) (C, N) formed in Ti-containing steels at high temperature.