Interrogating a New Strengthening Mechanism in an Additively Manufactured Steel

Selective electron beam melting (SEBM) is a powder-bed-fusion additive manufacturing (AM). Previous work has proven its robustness in obtaining the crack-free and refined microstructure over a wide spectrum of engineering materials. To date, almost all AM materials can only exhibit the mechanical property which is as good as the conventional means. Our study on SEBM S390 steel, a typical high-carbon and highly alloyed steel, has demonstrated a considerably increased hardness and bending strength when compared to those for conventional means in post-heat treated condition. But the unexpected property improvement cannot be understood based on our existing phase transformation theory. This SANS experiment aims to make quantitative statements about nano-cluster precipitates, combined with our already obtained data, to elucidate the new strengthening mechanism in SEBM S390 steel.