42CrMo高温塑性损伤机理及损伤模型

Damage mechanism and fracture prediction model of 42CrMo steel at high temperature

以42CrMo钢为研究对象,在Gleeble-1500D热模拟试验机上进行高温拉伸实验,研究了变形温度为900℃、950℃、1 000℃、1050℃、1100℃、1150℃,应变速率为0.01s-1、0.1s-1、1s-1、10s-1条件下的高温变形行为,采用Gleeble Fracture Limit(GFL)方法得到相应的应力、应变参数,基于Normalized Cockcroft&Lathamm损伤模型,计算得到不同变形温度和不同应变速率时的临界损伤值,考虑变形温度和变形速率对临界损伤值的影响引入了Zener-Hollomon参数,得到临界损伤值与lnZ值之间的高温损伤模型。采用扫描电镜对拉伸断口进行断口形貌观察,发现大量韧窝及夹杂物的存在,分析得到该断裂机制为韧性断裂。

The hot deformation behaviors of 42 CrMo steel were studied through tensile experiments on Gleeble-1500 Dthermal simulation machine with the temperature from 900℃to 1150℃ and the strain rate from 0.01s-1 to 10s-1.The stress and strain data can be calculated by the method of Gleeble Fracture Limit（GFL）,and the critical damage values corresponding with temperatures and strain rates were calculated by using Normalized Cockcroft ＆ Lathamm ductile fracture criterion and the experimental parameters.The Zener-Hollomon parameter was introduced to study the effect of temperature and strain rate on the critical damage values,and the relationship of the critical damage values and the value of lnZ is obtained.In order to further study the mechanism for damage,the tensile fracture morphology of tensile fracture was observed using SEM,and it is found that a large number of dimples and inclusions exist,which indicates the ductile fracture mechanism.