Influence of Heat Exposure Post-Laser Surface Melting on the Microstructure, Tribological, and Mechanical Behavior of New Modified AlSiMg Powder Alloy
摘要
This research investigates the microstructure, microhardness, and tribological behavior of a gas-atomized Al-13Si-0.9 Mg alloy modified with transition metals (TM) (2.8% Cu, 1.5% Fe, 1.8% Ni, 1.2% Mn) following laser surface melting (LSM). Altering Al-Si alloys with TM produces many intermetallic phases, enabling these materials to be viable for heat-resistant applications. The procedure was conducted utilizing a Nd:YAG pulsed laser. After the LSM, the samples were exposed to heating at 200, 300, and 400 °C and for holding time of 1, 2, 4, 8, 16 h. Microstructural investigation of the laser-treated alloy disclosed fine equiaxed α-Al grains beside primary Si crystals and eutectic Al-Si, and compacted intermetallic phases, such as α-Al(Mn,Fe)Si and Al3(Ni,Cu) in the overlapped zones, with minimal changes in phase composition during heat exposure. Microhardness tests indicated that the as-LSMed sample demonstrated a high microhardness of 177 HV0.05, which diminished to 117 HV0.05 following a 16-h exposure to 400 °C, attributed to stress relaxation and coarsening of the Si phase. In contrast, heating at 200 °C elevated microhardness to 205 HV0.05, due to artificial aging. Tribological testing revealed improved wear resistance and a stable coefficient of friction at 200 °C, with a decrease in wear rate from 6.1 × 10−3 to 2.1 × 10−3 mm3/N m. However, excessive softening at 400 °C led to poor tribological performance.