Microstructure and mechanical behavior of the laser synthesized composites modified by micro/nano scale rare earth oxides

Abstract Micro- and nano-scale rare earth oxides (REOs) modified composites were fabricated by laser scanning the preplaced materials, similar to the process in selective laser melting (SLM). To conduct the comparative study on the effect of different REOs, single-layer composites were prepared on Ti-6Al-4V alloy with Ni60A+10 wt.% B4C mixture as the basic material and different REOs as the additives. Experiments with micro- and nano-scale REOs (Nd2O3, La2O3) demonstrated benefits in refining the microstructure, improving both the micro-hardness and wear property of the composites, amongst which the nano-scale REOs show better performance. Compared with the composite without REOs addition, the composite modified with 1 wt. % nano-La2O3 exhibited the finest microstructure. The mean micro-hardness increased by ~36.0% from 1058 HV0.2 to 1439 HV0.2, and the wear resistance was improved by 38.5% based on the wear volume loss. The better refining effect of the nano-scale REO was mainly attributed to the small particle size, which was more dispersive in the preplaced materials for increased nucleation. This study is not only useful for surface strengthening of titanium alloys, but also provides inspiration for fabricating bulk composite materials with suitable REO additives.