Al₂O₃ nanoparticle-reinforced Al-12Si matrix composites were successfully fabricated by hot pressing and subsequent hot extrusion. The influence of weight fraction of Al₂O₃ particles on the microstructure, mechanical properties, and the corresponding strengthening mechanisms were investigated in detail. The Al₂O₃ particles are uniformly distributed in the matrix, when 2 and 5 wt. % of Al₂O₃ particles were added to the Al-12Si matrix. Significant agglomeration can be found in composites with 10 wt. % addition of Al₂O₃ nanoparticles. The maximum hardness, the yield strength, and tensile strength were obtained for the composite with 5 wt. % Al₂O₃ addition, which showed an increase of about ~11%, 23%, and 26%, respectively, compared with the Al-12Si matrix. Meanwhile, the elongation increased to about ~30%. The contribution of different mechanisms including Orowan strengthening, thermal mismatch strengthening, and load transfer strengthening were analyzed. It was shown that the thermal mismatch strengthening has a more significant contribution to strengthening these composites than the Orowan and load transfer strengthening mechanisms.

In order to better understand how a high energy input and a fast cooling rate affect the geometric morphology and microstructure of laser cladding aluminum composite coatings, a three-dimensional (3D) transient finite element model (FEM) has been established to study the temperature field evolution during laser cladding of AlSiTiNi coatings on a 304 stainless steel substrate. In this model, a planar Gauss heat source and a temperature selection judgment mechanism are used to simulate the melting and solidification process as well as the geometric morphology of the laser cladding coatings. The differences in physical characteristics of the cladding materials before and after melting are considered. The results of thermal simulations, including temperature history, temperature gradient, and solidification rate, of the laser cladding coatings are investigated. Corresponding experiments, conducted using an IPG-YLS-5000 fiber laser, are used to verify the simulation results. The experimental observations agree well with the theoretical predictions, which indicates that the established model is valid.