Effect of uniaxial load on microstructure and mechanical properties of Thixo-joint AISI D2 tool steel

Abstract

Tool steels are commonly used to cut metal materials due to their distinctive hardness, resistance to abrasion and deformation. However, tool steels are difficult to be joined using conventional fusion welding process. In this study, a thixotropic property of metal was utilised to butt-join an AISI D2 tool steel by using uncommon direct partial re-melting (DPRM) method. A high frequency of induction heating is used to apply the DPRM method. From the recent study, there are many methods in achieving the globular microstructure with the success of semi-solid joining process. Though, very less information on the microstructural effect of semi-solid joining on the mechanical properties was reported. This study aims to analyse the effect of uniaxial force on the microstructural evolution and mechanical properties of the thixo-joint of D2 tool steel. The microstructural analysis showed the diffusion occurred between the grains of the thixo-joint sample with 2.5 N uniaxial force. The maximum strength of the thixo-joint sample with force was 652 MPa. This was slightly higher than the as-received sample and the thixo-joint sample without force. The average hardness value of the thixo-joint sample was 400 HV due to the transformation of ferrite to the metastable austenite.