Selective laser melting additive manufacturing of in situ Al 2 Si 4 O 10 /Al composites: Microstructural characteristics and mechanical properties

Abstract

The advanced selective laser melting technology was employed to prepare in situ Al based composites. Relationship among selective laser melting processing parameters, microstructures and resultant mechanical properties had been established. It turned out that in situ Al₂Si₄O₁₀/Al composites were successfully fabricated by selective laser melting of Al₂O₃/AlSi10Mg composite powders. Due to the overlap between neighboring tracks and the remelting of previously solidified layers, two distinguished zones consisting of track core and track overlap were produced in laser induced melt pool. The two zones, respectively experienced different thermal histories, thus leading to the variation of cooling rate, which had a significant influence on the microstructural development and resultant mechanical performances. The track core mainly consisted of remarkably refined cellular dendritic Al matrix decorated with uniformly distributed ring-structured Al₂Si₄O₁₀ reinforcements, while the track overlap was characterized with comparatively coarse columnar dendritic Al matrix as well as the coarse Al₂Si₄O₁₀ reinforcements. At the optimal v of 500 mm/s, the obtained dynamic nanohardness (H _d ) of track core (H _d  = 3.79 GPa) and track overlap (H _d  = 3.52 GPa) for selective laser melting processed composites part both showed tremendous enhancement upon that of unreinforced Al part (H _d  = 0.58 GPa). The dry sliding wear tests indicated that the optimally prepared Al₂Si₄O₁₀/Al composites part exhibited excellent wear performance with a considerably low coefficient of friction of 0.32 and a significantly reduced wear rate of 4.52 × 10⁻⁵ mm³ N⁻¹ m⁻¹. The formed consecutive protective adherent tribolayer on the worn surface and the significantly enhanced hardness of the composites well accounted for the superior wear performance.