Research on the microphysical mechanism of metal magnetic memory testing through 45 # steel under compressive stress

To explore the microphysical mechanism of metal magnetic memory testing (MMMT) technique, the effect of compressive stress on the domain structure in 45# steel specimen and the pinning effect of stress-induced defects on domain walls (DWs) were investigated by in-situ Lorentz Transmission Electron Microscopy (LTEM). The changes in domain structure and defects are observed simultaneously. And the deformation and magnetic moment distribution of the specimen under compressive stress were measured and analyzed. The results show that, the rotation of magnetic moment corresponding to the deformation of the specimen can greatly reduce the magnetoelastic energy according to the calculation of magnetoelastic energy. When stress is removed, the domain structures do not restore, and DWs' pinning effect of defects could be clearly observed. The results provide a vigorous support for the memory effect of ferromagnetic material on historical stress.