Abstract: The surface properties of ZM5 Mg-base alloy were modified by laser cladding with Al+Y powder. Laser cladding was carried out with a 5kW continuous wave CO₂ laser by melting the preplaced powder mixture of Al and Y. Following laser cladding, the cladding zone was characterized by a detailed microstructural observation and phase analysis. Moreover, the microhardness and element distribution were evaluated in detail. The surface modified layer consists of Mg₁₇Al₁₂  and Al₄MgY phases, while α-Mg and Mg₁₇Al₁₂ in the substrate. The microhardness of the cladding zone was significantly enhanced as high as HV122-180 as compared to HV60-80 of the substrate region. The maximal hardness about HV224 is in the interface due to the formation of intermetallic Mg₁₇Al₁₂ phase. The microstructure is refined and Mg diffuses into the cladding material which leads to the formation of Mg₁₇Al₁₂.

Key words:  laser cladding; ZM5 Mg base alloy; rare earth; Al+Y powder;  microstructure