Study of Laser Alloying of Preplacing Al-Y Powder on ZM5 Alloy Substrate
Laser alloying of preplacing Al-Y powder on ZM5 magnesium alloy was carried out with different powder thickness by a CO2 laser in order to improve the corrosion resistance in salt-water(NaCl) solution.The alloying process,the microstructure and the composition were studied.The obtained samples were subjected to immersion tests.The results show that the phases of coating layer consists of Mg17Al12,Al2Y,Al and Mg.The relative proportion of Al2Y increases with the increase of preplaced powder thickness,while the relative proportion of Mg17Al12 decreases.From microscopic point of view,the geometric characteristics are related to the dilution.A good metallurgical bonding interface is obtained.The rapid solidification caused small and white yttrium-containing phases are formed in the alloying layer in different forms.And the microhardness of the alloying zone can be up to 250-325HV,but that of the substrate is only 80-100HV.The corrosion resistance of the alloying samples is enhanced in comparison to the untreated ZM5 substrate.