Microstructure and Properties of Al-Ti-TiB₂ Laser-Cladding Layer on Surface of AZ31 Magnesium Alloy

Mixed powders of aluminum, titanium, TiB₂ with mass ratio of 1.0:3.0:0.5 were cladded on surface of AZ31 magnesium alloy by using a high energy laser with different powers (2.5, 3.0 kW). The microstructure, phase composition, hardness and corrosion resistance of the cladding layer were studied. The results show that during the laser cladding, the aluminum reacted with the titanium to form Al₃Ti phase. Meanwhile, the aluminum reacted with the magnesium to form Al_0.56Mg_0.44 phase and Al₁₂Mg₁₇ phase at the laser powers of 2.5 kW and 3.0 kW, respectively. The TiB₂ retained the original crystal structure. The cladding layer had a finer Al₃Ti phase at the laser power of 3.0 kW than at the laser power of 2.5 kW, and showed a better metallurgical bonding by the formation of a eutectic structure layer between the cladding layer and the magnesium alloy substrate. The laser power had little influence on the hardness of the cladding layer; the hardness increased and then decreased with the distance to the surface increasing. The laser cladding can effectively improve the corrosion resistance of AZ31 magnesium alloy. The corrosion resistance of the cladding layer at the laser power of 3.0 kW was better than that at the laser power of 2.5 kW.