Enhancing the Homogenized Diffusion of Chromium in Alloy Steel Ingot by Forging

The effects of forging on the diffusion of chromium (Cr) in alloy steel ingot are studied by diffusion model with finite element method (FEM) and verified by the experimental observations. Calculated results show that forging can enhance the diffusion of Cr in alloy steel ingot during the homogenization treatment, which is attributed to the geometry change and the increased diffusion coefficient caused by recrystallization. The geometry change caused by the forging is a factor to increase the diffusivity (from the high concentration region to the low one) of Cr. But, the diffusion coefficient of Cr in the deformed sample is obviously enhanced, the diffusivity is two orders of magnitude higher than that caused by geometry change. The enlarged diffusion coefficient is originated from the recrystallization, which plays a major role in enhancing the diffusion during the homogenization treatment. The experimental results are confirmed with the calculated predicts, the calculated deviation is less than 7%. It is shown that the effect of recrystallization is a new mechanism of enhancing the diffusion by forging .The theoretical explanations of the diffusion mechanism enhanced by forging are also proposed.