Structural design, interfacial behavior and mechanical properties of bimetallic nacre-like structures by laser powder-bed fusion

Abstract

The nacre-like (NL) structure exhibits unique performance in preventing the catastrophic crack growth and improving the strengthening/toughening of the overall structure. In this study, the In718/316LSS bimetallic NL structures were first fabricated by a powder laying-absorption multiple-material additive manufacturing technology based on laser powder-bed fusion, and the stress release mechanism was revealed. The NL structures with optimal geometric parameters was obtained by calculation and simulation: the hard-phase inclination angle of 15 °, the hard-phase volume fraction of 70%, and the lamellar length-width ratio of 2. Due to the remelting effect, the same-layer bimetallic interfaces in NL structures showed strong metallurgical bonding with significantly grain refinement. The interlocking NL structure exhibited superior mechanical properties of 751.82 MPa in tensile strength and 25.14% in elongation, compared with the base alloys and the non-interlocking NL structure. Moreover, abnormal variation of work hardening rate in NL structures attributed to the stress concentration and release behavior, caused by the multi-cracks initiation and cracks deflection during deformation of the interlocking structure. By the stress concentration-release effect, the NL structure not only achieved the strengthening and toughening, but also improved the crack tolerance to avoid the sudden fracture failure.