ⓒ 2011 Journal of Magnetics Effect of Isothermal Aging on the Magnetic Properties of 1Cr-0.5Mo Steel

Magnetic properties and Rockwell hardness of 1Cr-0.5Mo steel have been investigated as a function of isother-mal aging time. Our results showed that coercivity, hysteresis loss and Rockwell hardness in the aged samples decreased as aging time increased. This phenomenon was analyzed using optical microscopy and scanning elec-tron microscopy. A significant diffusion of Cr and Mo atoms formed M2C and M7C carbides, lowering the matrix strength. M2C and M7C carbides partially segregated inside grains, diffused into grain boundaries, and finally resulted in a soft ferrite matrix and a hard grain boundary. The magnetic and mechanical softening of the matrix is likely to govern the properties of the sample more than the hardening of the grain boundary by carbide precipitations