Abstract
Copper/steel is a typical bimetal functional material,combining the excellent electrical and thermal con-ductivity of copper alloy and the high strength and hardness of stainless steel.There has been recent interest in manufacturing copper/steel bimetal by directed energy deposition (DED) due to its layer-by-layer method.However,cracks tend to form on the copper/steel interface because of the great difference in thermal expansion coefficient and crystal structure between copper and steel.In this work,interfa-cial characteristics and mechanical properties of the copper/steel bimetal were studied from one layer to multilayers.The laser power has a great influence on the Cu element distribution of the molten pool,affecting the crack formation dramatically on the solidification stage.Cracks tend to form along colum-nar grain boundaries because of the Cu-rich liquid films and spherical particles in the cracks.Crack-free and good metallurgical bonding copper/steel interface is formed at a scanning velocity of 800 mm/min and the laser power of 3000 W.The ultimate tensile strength (UTS) and the break elongation (EL) of the vertically combined crack-free copper/steel bimetal are 238.2 ± 4.4 MPa and 20.6 ± 0.7％,respec-tively.The fracture occurs on the copper side instead of the copper/steel interface,indicating that the bonding strength is higher than that of the Cu-Cr alloy.The UTS of the horizontally combined crack-free copper/steel bimetal is 746.7 ± 22.6 MPa,which is 200％ higher than that of the Cu-Cr alloy substrate.The microhardness is 398.6 ± 5.4 HV at the steel side and is 235.3 ± 64.1 HV at the interface,which is 400％ higher than that of the Cu-Cr alloy substrate.This paper advances the understanding of the inter-facial characteristics of heterogeneous materials and provides guidance and reference for the fabrication of multi-material components by DED.
基金项目
Human Spaceflight Program of China(D050302)
Military Industry Stability Support project(2019KGW.YY4007Tm)
Analytical and Testing Center of HUST for the EPMA analysis()
NETL
NSTL
维普
万方数据