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Mintz于1997年报道了一个有趣的试验现象:随着拉伸应变速率的增加,奥氏体钢韧性降低,铁素体钢韧性反而提高。其机制未得到解释。通过计算试验钢中P原子的非平衡晶界偏聚临界时间,结果发现奥氏体钢拉伸前热过程的等效时间短于其临界时间,而铁素体钢的等效时间长于其临界时间。由于奥氏体钢和铁素体钢分别在850和800℃等效时间最接近临界时间,韧性最低,即试验钢的热塑性降低都是由于非平衡晶界偏聚的临界时间造成的。应变速率降低,弹性应力作用时间增加。晶界偏聚量改变,热塑性降低的程度也随之改变。即热塑性降低的程度随应变速率的改变是由应力引起的非平衡晶界偏聚决定。
An interesting experiment was reported by Mintz in 1997: As the tensile strain rate increases, the ductility of austenitic steels decreases and the toughness of ferritic steels instead increases. The mechanism is not explained. By calculating the critical time of non-equilibrium segregation of P atoms in test steel, the equivalent time of austenitic steel before hot-stretching is found to be shorter than the critical time, while the equivalent time of ferritic steel is longer than its critical time. Since the equivalent time of austenitic steel and ferritic steel at 850 and 800 ℃ respectively is the closest to the critical time, the lowest toughness is the thermoplastic decrease of the test steel due to the critical time of non-equilibrium grain boundary segregation. Strain rate decreases, the elastic stress action time increases. Grain boundary segregation changes, the degree of thermoplastic reduction also will change. That is, the degree of thermoplastic decrease with strain rate is determined by stress-induced non-equilibrium grain boundary segregation.