低频交变磁处理降低钢材内应力的微观机理

磁场处理被许多研究者用于提高材料的力学性能并取得了一定效果。作者首次运用磁处理方法进行降低材料内应力的研究。结果表明，不同的处理方法，如高强磁脉冲处理和低频交变磁场处理都能够不同程度地降低材料内部存在的残余应力，而且其降低残余应力的方式与常规的热处理有本质的不同。本文定量研究了低频交变磁处理方法降低残余应力的程度、特点和工艺参数。通过透射电镜分析，着重观察了对30CrMnSiA进行磁处理时处理前后材料内部的位错运动规律。在经过磁处理后的试样中，其明显的胞壁结构消失，位错分布均匀化；整体位错密度与处理前相比变化不大。根据上述观察和宏观试验结果，对磁处理降低残余应力的特点和微观结构进行了分析了讨论，认为磁场作用下的位错均匀化是磁处理降低残余应力的主要原因。

Micro Mechanism of Reducing Residual Stress by Low Frequency Alternating Magnetic Treatment

Low frequency alternating magnetic field is initiatively used by the authors to process the welded samples with internal residual stress.Experiments show that both strong pulsed magnetic treatment and low frequency alternating magnetic treatment can reduce the residual stress in materials to some extent.The way that the magnetic treatment reduces the residual stress is different essentially from that by thermal methods.Magnetic treating parameters and magnitude of stress relaxation are investigated quantitatively in this article.The microstructure change of a commercial steel during magnetic treatment is observed by transmission electron microscope and discussed from the point of view of the dislocation behavior in the processed material.The cell wall structure of dislocation in a tensively pre stressed specimen of a commercial steel 30CrMnSiA disappears and the dislocation distribution is harmonized although the dislocation density keeps almost unchanged.This harmonization of dislocation distribution is considered to be one of the main factors which lead to the residual stress reduction.