Effect of Inclusions on Fracture Behavior of LZ50 Railway Axle Steel during High-Temperature Tension

The effect of non-metallic inclusions on the fracture behavior of LZ50 railway axle steel at high temperature was studied by combining experiment and finite element method. The evolution process of the micro void initiation, growth and coalescence was observed, and the strain characteristics around the void were analyzed. It is found that the non-metallic inclusions are broken or debonded from the matrix to form micro voids during deformation. The strain around the void is enlarged and concentrated, leading to void growth and coalescence; then, the continuity of the matrix is destroyed to make the fracture occur in advance. The effects of initial void morphology on the matrix fracture behavior were further studied. It is found that the larger the initial void diameter, the closer the axial distance is to the center of the specimen, the easier the matrix is to fracture. However, changing the radial position of the void has little effect on the matrix fracture behavior. When multiple voids exist, void coalescence is likely to occur, which will intensify the discontinuity of the matrix and accelerate the matrix fracture.