Unraveling the dual cracking mechanism of 316L/CuSn10 heterostructures fabricated by laser powder bed fusion

A comprehensive understanding of cracking mechanisms and the prevention of interfacial microcrack formation are imperative for additive manufacturing of high-performance multi-material heterostructures. This study systematically investigated 316L/CuSn10 heterostructures and identified solidification cracking and solid-state cracking as the predominant mechanisms. Solidification cracking is closely linked to the copper content within the mixing zone, particularly evident at 10% copper content, which heightens sensitivity to solidification cracking due to the widening of intergranular spacing and the elongation of the liquid film channel. Solid-state cracks tend to initiate from pre-existing solidification cracks, propagate along high-angle grain boundaries (HAGBs), particularly within a specific misorientation angle range of 20°-50°, terminating eventually at low-angle grain boundaries (LAGBs). This is mainly controlled by the distribution of dislocations at crack tips, which are dispersed within the grains at LAGBs, and the resulting back stress contributes to crack termination. These findings contribute valuable insights into the cracking mechanisms in heterostructures and offer guidance for the fabrication of crack-free steel-copper components.