Microstructures and mechanical properties of nano-TiC/Ti-refined Al-Mg alloys prepared by wire arc additive manufacturing

In the current study, an Al-Mg alloy refined with a nano-TiC/Ti grain refiner was successfully printed by cold metal transition wire arc additive manufacturing (CMT-WAAM). The effects of the nano-TiC/Ti grain refiner on the microstructure and mechanical properties of the CMT-WAAM-prepared Al-Mg alloy were studied. The results indicated that the nano-TiC/Ti grain refiner has a significant refining effect on Al-Mg alloy and refined the coarse columnar crystals into uniform fine equiaxed crystals. The average grain size of the CMT-WAAM Al-Mg alloy refined with the 0.6 wt% nano-TiC/Ti grain refiner decreased from 53.06 mu m to 25.32 mu m (yz plane), and the average grain size in the xy plane decreased from 52.00 mu m to 25.80 mu m. The excellent grain refinement effect of the nano-TiC/Ti grain refiner was attributed to the presence of TiC particles at the grain, which acted as heterogeneous nucleation sites and improved the nucleation rate. Moreover, TiC particles located at the grain boundary inhibited the growth of the grain boundary. The mechanical properties, i.e., the tensile and yield strength, were improved by 20-25%, and there was an increase in the microhardness (similar to 9.5%) of the CMTWAAM Al-Mg alloy refined with the 0.6 wt% nano-TiC/Ti grain refiner.