高应变速率条件下1200MPa级冷轧双相钢塑性变形微观机理的研究

通过在CMT4105试验机上进行准静态拉伸试验,在Hopkinson拉杆试验机上进行动态拉伸试验。在常温下,对DP1200冷轧双相钢进行应变速率为1×10~(-4) s~(-1)、1×10~(-3) s~(-1)、1×10~(-2) s~(-1)的准静态拉伸试验,以及应变速率为500 s-1、1 000 s-1、2 250 s-1的动态拉伸试验,并对拉伸断口进行形貌分析。结果表明:DP1200冷轧双相钢在准静态和动态变形条件下,随应变速率的增大,屈服强度s0.2从723 MPa增加到998 MPa,抗拉强度sb从1 205 MPa增加到1 515 MPa,断后伸长率从9.0%下降到7.7%,屈强比从0.60上升到0.66。准静态和动态拉伸的韧断口都呈现窝状,为韧性断口。应变速率为1×10~(-4) s~(-1)、1×10~(-3) s~(-1)、1×10~(-2)s~(-1)、500 s~(-1)、1 000 s~(-1)、2 250 s~(-1)断口韧窝平均尺寸分别为7.5μm、7.2μm、6.9μm、4.3μm、3.5μm和2.6μm,准静态拉伸不同应变速率下韧窝形貌变化不大,动态拉伸条件下随应变速率的增加断口韧窝变深。

Plastic Deformation Microscopic Mechanism of Cold Rolled Dual Phase Steel DP1200 under High Strain Rate Deformation

Quasi static tensile experiments are done by CMT4105, and dynamic tensile experiments are done by Hopkinson tester. At room temperature, strain rate of the quasi static tensile experiments of DP1200 cold rolled steel are 1×10?4 s?1, 1×10?3 s?1, 1×10?2 s?1;strain rate of dynamic tensile experiments are 500 s?1, 1 000 s?1, 2 250 s?1. And fracture morphology analysis is done. The results reveals that with the increase of the strain rate on the conditions of quasi static tensile experiments and dynamic tensile experiments of the DP1200 cold rolled steel, the tensile strength increases from 1 205 MPa to 1 515 MPa, the yield strength increases from 723 MPa to 998 MPa and the yield strength ratio increases from 6.0 to 6.6, while the elongation decreases from 9.0%to 7.7%. Fracture morphology is toughening nest under quasi static tensile and dynamic tensile conditions. When the strain rates are 1×10?4 s?1,1×10?3 s?1,1×10?2 s?1,500 s?1,1 000 s?1,2 250 s?1,the average sizes of fracture toughness are 7.5μm, 7.2μm, 6.9μm, 4.3μm, 3.5μm and 2.6 μm. Fracture morphology changes little with the different strain rates under quasi static tensile condition, while the increasing strain rates make the toughening nest deeper under dynamic tensile conditions.