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Selective laser melting (SLM) was successfully applied to fabricate strong and ductile reduced activation ferritic/martensitic (RAFM) steel by introducing heterogeneous multi-/bimodal microstructure. The SLM-built RAFM steel exhibited an excellent combination of strength and ductility (i.e. yield strength of 1053 ± 4.7 MPa and elongation of 16.9 ± 0.4%), well surpassing the previously reported counterparts. The superior strength was expected from the refined grains and lath martensites, and the high ductility was associated with the improved dislocation-controlled strain hardening capability. This work provides a basis for developing high-performance RAFM steel by microstructural design via SLM.

Selective laser melting (SLM) was successfully applied to fabricate strong and ductile reduced activation ferritic/martensitic (RAFM) steel by introducing heterogeneous multi-/bimodal microstructure. The SLM-built RAFM steel exhibited an excellent combination of strength and ductility (i.e. yield strength of 1053 ± 4.7 MPa and elongation of 16.9 ± 0.4%), well surpassing the previously reported counterparts. The superior strength was expected from the refined grains and lath martensites, and the high ductility was associated with the improved dislocation-controlled strain hardening capability. This work provides a basis for developing high-performance RAFM steel by microstructural design via SLM. A new strategy, refers to heterogeneous multi-/bimodal microstructure, is proposed to develop strong and ductile RAFM steel via SLM and the achieved superior mechanical properties overcome the classic strength-ductility trade-off. [ABSTRACT FROM AUTHOR]

Selective laser melting (SLM) was applied to fabricate high-strength and ductile reduced activation ferritic/martensitic (RAFM) steel via modification of heterogeneous microstructure that consists of domains of fine and coarse grains as well as lath martensites, but with different grain morphology in respond to the variation in the scanning strategy and resultant thermal history. The SLM-built RAFM steel exhibited an enhanced strength-ductility synergy with high yield strength of 967 MPa and high elongation of 15.1% under a meander scanning strategy, surpassing the previously reported counterparts, which was ascribed to the refined microstructure and improved strain hardening. In contrast, an island scanning strategy deteriorated the ductility down to 3.8% arising from the oriented alignment of columnar coarse grains around island, which initiated micro-voids and cracks during deformation and finally gave rise to a premature failure. This work proposed the microstructural design principles for additively manufacturing high-performance RAFM steels and is expected to facilitate their application in the fusion reactor. [ABSTRACT FROM AUTHOR]