预应变对高强度低合金钢性能和组织的影响

Influence of pre-strain on properties and microstructure for high strength low alloy steel

以高强度低合金钢HC340LA为研究对象,对其微观组织及力学性能进行了分析;对3个方向的单向拉伸试样分别施加0%、5%、10%、15%的预应变,卸载后进行二次拉伸至试样断裂,获取应力-应变曲线,并提取力学性能、加工硬化等关键参数,获取预应变的影响规律;对均匀变形区域的微观组织进行观察,获取预应变对组织的影响。结果表明:材料存在屈服平台和明显的吕德斯带;强度随着预应变的增加而增大;断后伸长率在5%预应变时有所下降,但随着预应变的继续增加则开始增大;瞬时加工硬化值随着预应变量的增大迅速降低,并且存在明显的变化差异;铁素体晶粒随预应变量的增加发生尺寸变化,而珠光体的尺寸并未发生明显变化,但随着铁素体的变形,其排布方向出现了变化。

For HC340LA high strength low alloy steel,its microstructure and mechanical properties were analyzed,and 0%,5%,10%and 15%pre-strains were applied to the uniaxial tensile samples in three directions,respectively.Then,after unloading,the samples were subjected to secondary stretching until the fracture of samples,and the stress-strain curves were obtained.Furthermore,the key parameters such as mechanical properties and work hardening were extracted to obtain the influence laws of pre-strain,and the microstructure of uniform deformation zone was observed to obtain the influence of pre-strain on the microstructure.The results show that there is a yield platform and obvious Lüders band.The strength of material increases with the increasing of pre-strain.The elongation after fracture decreases at the prestrain of 5%,but it increases with the continued in creasing of pre-strain.The instantaneous work hardening value rapidly decreases with the increasing of pre-strain,and there is a significant difference in variation amount.The size of ferrite grains changes with the increasing of prestrain amount.The size of pearlite does not show significant changes,but its arrangement direction changes with the deformation of ferrite.