Interfacial characteristic and mechanical performance of maraging steel-copper functional bimetal produced by selective laser melting based hybrid manufacture

A combination of selective laser melting (SLM) additive manufacture and subtractive process was explored to produce maraging steel copper bimetal. Relationships among laser parameter, interfacial characteristic and mechanical performance are elucidated. A metallurgical bonded interface with a 30-40 mu m inter-diffusion region is formed. Gradient submicro grains with strong < 111 > orientation exhibit at the interface, which owe to high cooling rate and temperature gradient caused by high thermal conductive copper. A selected region of the interface was extracted by focused ion beam(FIB) for interfacial bonding analysis. The bonding mechanism is revealed and illustrated in detail. Interfacial intense Marangoni flows pull the copper toward the molten pool of maraging steel and the liquid maraging steel penetrates into the melting copper, which contributes to interfacial bonding. The bonding strength of hybrid processed bimetals are evaluated. Fracture in tensile is not present at the interface but on the copper side. The highest flexural strength reaches 557 MPa, which is slightly higher than that of the copper. Effects of parameter on fracture behaviors are also elucidated. This hybrid manufacture increases the productivity and functionality of the direct SLM-produced part, and provides a new approach for producing high-performance functional dissimilar bimetals based on laser additive manufacture. (C) 2018 Elsevier Ltd. All rights reserved.