电流脉冲对45碳钢试样位错密度和残余应力的影响

Effects of electric current pulse on dislocation density and residual stresses of 45 carbon steel workpieces

研究了电流脉冲对淬火45碳钢试样位错密度和表面残余应力的影响。根据XRD图谱,采用Modified Williamson-Hall(MWH)方法计算位错密度,进一步结合微观组织结构,分析了位错密度和残余应力的关系。结果表明,电流脉冲处理前后,位错密度由1.21×1015m-2变为0.80×1015m-2,表面残余应力σx由-250 MPa降低到-142 MPa,σy由-363 MPa降低到-172 MPa。与热处理相比,电流脉冲处理的试样位错密度和残余应力的降低率都比较大,表明电流脉冲除了产生热作用外,还产生了非热作用。位错密度和残余应力存在一定关系,符合Kocks-Mecking模型。电流脉冲处理过程中,位错激活运动,导致位错湮灭,位错密度降低,是残余应力降低的主要因素。

The effects of electric current pulse( ECP) on dislocation density and residual stresses of quenched 45 carbon steel were studied. The dislocation density was evaluated by the Modified Williamson-Hall( MWH) method based on XRD pattern. The relationship between dislocation density and residual stresses was analyzed according to the microstructure. The results show that the dislocation density decreases from 1. 21 × 1015m- 2to 0. 80 × 1015m- 2caused by ECP treatment,and the residual stress σxis changed from- 250 MPa to-142 MPa,and σyis changed from- 363 MPa to- 172 MPa. The reduction rates of dislocation density and residual stresses of the steel treated by ECP are larger than those of the steel after thermal treatment,which shows that other effects exist except thermal effect.Furthermore,the relationship between dislocation density and residual stresses conforms to Kocks-Mecking model. The dynamic behavior of dislocations is promoted by ECP leading to annihilation of dislocations. Hence,the dislocation density decreases,which is the main reason of the decrease of residual stresses.