Enhanced strength and ductility of high chromium cast iron/low carbon steel bimetal by heterostructure design

Abstract

In this study, the heterostructured high chromium cast iron (HCCI)/low carbon steel (LCS) bimetal was designed by optimized heat treatment process. The microstructure, mechanical properties and deformation behavior of bimetal were studied. The bonding zone of HCCI/LCS bimetal is comprised of ferrite and pearlite, while the diffusion zone of HCCI mainly consists of M23C6 and ferrite due to the diffusion of C atoms from the HCCI to the LCS. The shear strength value of the bimetal is 395.2 MPa and no microcracks were observed at the interface. The tensile strength and total elongation of the bimetal are 452.1 MPa and 26.2 %, respectively. The analysis of the deformation behavior shows that the back stresses originate from the cooperative effect between the hard and soft zones, which improves the overall strength and ductility of the bimetal. In the deformed samples, large plastic deformations and stress concentrations were observed in the soft zones due to the dislocation were blocked in the hard zones, which confirmed the typical hetero-deformation induced (HDI) strengthening. The present work sheds light on heterostructure of HCCI/LCS bimetal that can be feasibly employed, and it could guide the optimization of mechanical performance of a wide range of fragile alloys for toughness engineering.