Selective laser melting (SLM), due to its unique additive manufacturing processing philosophy, demonstrates a high potential in producing bulk-form nanocomposites with novel nanostructures and enhanced properties. In this study, the nanoscale TiC particle reinforced AlSi10Mg nanocomposite parts were produced by SLM process. The influence of “laser energy per unit length” (LEPUL) on densification behavior, microstructural evolution, and wear property of SLM-processed nanocomposites was studied. It showed that using an insufficient LEPUL of 250 J/m lowered the SLM densification due to the balling effect and the formation of residual pores. The highest densification level (>98% theoretical density) was achieved for SLM-processed parts processed at the LEPUL of 700 J/m. The TiC reinforcement in SLM-processed parts experienced a structural change from the standard nanoscale particle morphology (the average size 75–92 nm) to the relatively coarsened submicron structure (the mean particle size 161 nm) as the applied LEPUL increased. The nanostructured TiC reinforcement was generally maintained within a wide range of LEPUL from 250 to 700 J/m and the dispersion state of nanoscale TiC reinforcement was homogenized with increasing LEPUL. The sufficiently high densification rate combined with the uniform distribution of nanoscale TiC reinforcement throughout the matrix led to the considerably low coefficient of friction of 0.38 and wear rate of 2.76 × 10−5 mm3 N−1 m−1 for SLM-processed nanocomposites at 700 J/m. Both the insufficient SLM densification response at a relatively low LEPUL of 250 J/m and the disappearance of nanoscale reinforcement at a high LEPUL of 1000 J/m lowered the wear performance of SLM-processed nanocomposite parts.
The selective laser melting (SIM), due to its unique additive manufacturing (AM) proc essing manner and laser-induced nonequilibrium rapid melting!solidification mechanism, has a promising potential in developing new metallic materials with tailored perform ance. In this work, SLM of the SiCIAlSilOMg composites was performed to prepare the Al-based composites with the multiple reinforcing phases. The influence of the SLM processing parameters on the constitutional phases, microstructural features, and mechanical peiformance (e.g., densification, microhardness, and wear property) of the SLM-processed Al-based composites was studied. The reinforcing phases in the SLMprocessed Al-based composites included the unmelted micron-sized SiC particles, the in situ formed micron-sized AUSiC4 strips, and the in situ produced submicron AfSiC4 particles. As the input laser energy density increased, the extent of the in situ reaction between the SiC particles and the Al matrix increased, resulting in the larger degree of the formation of Al4 SiC4 reinforcement. The densification rate of the SLM-processed Al-based composite parts increased as the applied laser energy density increased. The sufficiently high density (~96% theoretical density (TD)) was achieved for the laser linear energy density larger than 1000 Jim. Due to the generation of the multiple rein forcing phases, the ele vated mechanical properties were obtained for the SLM-processed Al-based composites, showing a high microhardness of 214 HVg j, a considerably low coefficient of friction (COF) of 0.39. and a reduced wear rate of 1.56 x 10 5 mm3 N 1 m~. At an excessive laser energy input, the grain size of the in situ formed AfSiC4 rein forcing phase, both the strip-and particle-structured AI4SiC4, increased markedly. The significant grain coarsening and the formation of the inteifacial microscopic shrinkage porosity lowered the mechanical properties of the SLM-processed Al-based composites. These findings in the present work are applicable and/or transferrable to other laserbased powder processing processes, e.g., laser cladding, laser metal deposition, or laser engineered net shaping.
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