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.

选区电子束熔化（Selective Electron Beam Melting，SEBM）属于粉床熔融型增材制造（Additive Manufacturing，AM）技术。此前研究已证实，该技术在宽泛的工程材料范围内均可制备无裂纹且显微组织细化的构件，具备优异的工艺鲁棒性。截至目前，几乎所有增材制造制备的材料，其力学性能仅能达到传统制造工艺的同等水平。我们针对典型高碳高合金钢S390钢的SEBM制备工艺开展的研究显示，在热处理后状态下，该工艺制备的S390钢的硬度与抗弯强度较传统工艺制备的同种材料有显著提升。但这种反常的性能提升无法通过现有相变理论得到合理解释。本小角中子散射（Small Angle Neutron Scattering，SANS）实验将结合已获取的实验数据，对纳米团簇析出相进行定量表征，以期阐明SEBM制备S390钢中新的强化机制。