Effect of volume ratio of liquid to solid on the interfacial microstructure and mechanical properties of high chromium cast iron and medium carbon steel bimetal

The high chromium cast iron and medium carbon steel bimetal was fabricated by liquid–solid casting technology. The effect of volume ratios of liquid to solid (6:1, 10:1 and 12:1) on the interfacial microstructure and mechanical properties of bimetal was investigated. The interfacial microstructure was analyzed using scanning electron microscope (SEM) and transmission electron microscope (TEM). The shear strength and microhardness in as-cast condition were studied at room temperature. The results show that the volume ratios of liquid to solid affect significantly the interfacial microstructure. When liquid–solid volume ratio was 6:1, the unbonded region was detected in interface region because the imported heat energy cannot support effectively the diffusion of element, whereas, when liquid–solid volume ratios reach 10:1 and 12:1, a sound interfacial microstructure was achieved by the diffusion of C, Cr, Mo, Cu and Mn, and metallurgical bonding without unbonded region, void and hole, etc. was detected. With the increase of liquid–solid volume ratio, the elemental diffusion activity improves, resulting in the increase of width of interface transition region. At the same distance from interface, with the increase of liquid–solid volume ratio, the microhardness is degraded in HCCI, but increased in MCS. The shear strength is also improved with the increase of liquid–solid volume ratio.

► Volume ratio of liquid to solid affects significantly the interfacial microstructure.
► Elemental diffusion activity is increased by increasing volume ratio.
► Mechanical property is improved by increasing volume ratio.