形变热处理对中碳Cr-Ni-W-Mo钢组织及力学性能的影响

为进一步提高中碳Cr-Ni-W-Mo钢的强塑性，采用Gleeble 3500热模拟试验机在700 ℃温度下进行变形量为20%~50%的形变热处理（TMT）。利用扫描电镜、透射电镜、电子背散射衍射对试验钢组织进行表征，利用拉伸试验机对拉伸性能进行测试，研究TMT工艺对其组织演变和力学性能的影响。结果表明：试验钢在TMT后的组织是包含回火马氏体、下贝氏体、残余奥氏体的复相组织，随着形变量增加，下贝氏体组织及残余奥氏体含量、位错密度相应增加，板条宽度减小；在相变强化、细晶强化及位错强化共同作用下，随着形变量增加，试验钢的强度增加，塑性升高；当形变量为50%时屈服强度达到1 733 MPa，抗拉强度达到2 243 MPa，伸长率为12.66％，与传统热处理相比，分别提高28.18%、12.88%和50.35%，获得了良好的强塑性匹配。

Effect of Thermo-mechanical Treatment on the Microstructure and Mechanical Properties of a Medium Carbon Cr-Ni-W-Mo Steel

In order to further improve the strength and ductility of the medium carbon Cr-Ni-W-Mo steel， the effect of thermo-mechanical treatment (TMT)，which was conducted at 700 ℃ with deformation from 20% to 50%，on the microstructure evolution and mechanical properties of medium carbon Cr-Ni-W-Mo steel was analyzed by scanning electron microscopy (SEM)，transmission electron microscopy(TEM)，electron backscattered diffraction (EBSD) and tensile test. The results show that the microstructures of steel after TMT processing contain the complex phases with tempered martensite，lower bainite and retained austenite.The fractions of lower bainite and retained austenite，and the dislocation density increase together with the refinement of martensite lath with the deformation increasing from 20% to 50%. Due to the coupling effects of phase transformation strengthening，fine grain strengthening and dislocation strengthening，the strength and ductility of steel are improved simultaneously with the increase in deformation. The steel processed by TMT with deformation of 50% has high strength and good ductility，and its yield strength，ultimate strength and elongation are 1 733 MPa， 2 243 MPa and 12.66%，respectively， which are improved by 28.18%，12.88% and 50.35% than those of the steel processed by conventional heat treatment，respectively.