Refined microstructure and enhanced mechanical performance of hybrid additive manufacturing Al-Cu-Mg alloys by multi-cycle friction stirring processing

A hybrid additive manufacturing (HAM) technology combined by friction stirring processing (FSP) and laser deposition melting (LMD) has been investigated. It can provide an attractive and cost-effective approach for aluminum engineering components. However, the mechanisms of the effects of different stirring strategies on microstructure and mechanical properties are still unclear. The effect of multiple repetitions in the process of FSP on the microstructure and mechanical properties of Al-Cu-Mg alloys prepared by LMD has been studied, and the unavoidable defects, such as pores and cracks are eliminated by repetitive FSPs, so as to refined microstructure as well as enhance the properties. Especially after 2 cycles of overlap-track full area lap friction stir processing (2C-FSP), the grain refinement reaches its optimal state, with a grain size of 2.57 μm and the average microhardness also reaches its optimal level (153.3 HV). At the same time, the ultimate tensile strength (UTS) was improved by 49.3 %, yield strength (YS) by 44.8 %, and elongation (EL) by 8.39 % compared with the deposition layer. Simultaneously, the dominant mechanisms of microstructural evolution and tensile property enhancement generated by hybrid additive manufacturing are revealed.