冷轧对M50钢马氏体/贝氏体复相组织与力学性能的影响

利用X射线衍射仪(XRD) 、扫描电镜(SEM) 、透射电镜(TEM)、室温拉伸和冲击性能测试研究了冷轧对M50钢马氏体/贝氏体(M/B)复相组织和性能的影响。结果表明:20%冷轧变形量的试样经等温淬火后具有最佳的抗拉强度(2535.7 MPa)和冲击性能(96.93 J),相比变形量为0%的试样,冲击吸收能量提高了约21%,抗拉强度提高了约5%。当变形量小于20%时,随着变形量的增加,M/B复相组织逐渐细化且在20%的冷轧变形量下组织最细;当变形量大于20%时,随着变形量的增加,贝氏体束减少,其对马氏体板条的分割作用减弱,导致组织呈现一定的粗化。

Effect of cold rolling on M/B duplex microstructure and mechanical properties of M50 steel

Effect of cold rolling on the M/B duplex microstructure and mechanical properties of M50 steel was investigated by means of X-ray diffraction, scanning and transmission electron microscopy, uniaxial tensile and Charpy impact tests. The results show that an excellent combination of ultimate tensile strength (2535.7 MPa) and impact property (96.93 J) is achieved by combining 20% cold rolling with austempering, of which the ultimate tensile strength increases by about 5% whereas the impact absorbed energy increases by about 21% compared with the specimen which is not cold rolled. The microstructure observation indicates that with the increase of cold rolling deformation (<20%), the microstructure becomes finer and the specimen with 20% cold rolling deformation shows the finest microstructure. However, when a higher cold rolling deformation (>20%) is applied, the amount of bainite sheaves decreases, which weakens the refinement of martensite and leads to some coarsening of microstructure.