Cu-Zr-Al-(Y, Ag) amorphous alloy ribbons of Cu_(50)Zr_(42)Al_8, Cu_(46)Zr_(47-x)Al_7Y_x(x=2, 5), Cu_(43)Zr_(42)Al_8Ag_7, and Cu_(43)Zr_(42)Al_8Ag_5Y_2 were prepared using the single roller melt-spinning method. The glass forming ability and non-isothermal crystallization behavior of the amorphous alloys were investigated by means of X-ray diffraction(XRD) and differential scanning calorimetry(DSC) in a continuous heating mode. The experimental results show that the glass forming ability and thermal stability of Cu-Zr-Al amorphous alloys are improved by adding minor amounts of Y and Ag, and the effect of Ag on the glass forming ability is more significant than that of Y. Compared to the Cu_(50)Zr_(42)Al_8 alloy, the width of the supercooled liquid region of the Cu_(46)Zr_(47-x)Al_7Y_x(x =2 and 5) alloys increased by 19 K and 30 K, respectively. The reduced glass transition temperature(Trg) and the parameter γ of the two alloys enhanced separately. Compared to the Cu_(50)Zr_(42)Al_8 alloy, the Trg and γ values of both Cu_(43)Zr_(42)Al_8Ag_7 and Cu_(43)Zr_(42)Al_8Ag_5Y_2 alloys enhanced noticeably up to 0.619, 0.417, and 0.609, 0.412, respectively. The crystallization activation energies of the amorphous alloys calculated by the Kissinger and Flynn Wall Ozawa equations increased with the addition of minor Y and Ag into the Cu_(50)Zr_(42)Al_8 alloy. The addition of Y and Ag significantly improved the thermal stability of the Cu_(50)Zr_(42)Al_8 amorphous alloy.
In order to improve the surface hardness and wear resistance of magnesium, Al-13%Si (mass fraction) alloy coating was deposited on pure magnesium by droplet spraying process. The microstructure was studied by electron probe microanalysis and X-ray diffraction. The micro-hardness and wear resistance of coating were investigated in comparison with those of the substrate. It is found that the coating layer is composed of α-Al cellular due to rapid solidification. Formation mechanism of the coating is due to the obstruction of diffusion by in-situ formed Mg 2 Si in interfacial layer. The coating exhibits higher hardness compared to that of the Mg substrate. As result of its high hardness, the wear resistance of the coating layer is about ten times that of the substrate. The droplet spraying process demonstrates that the magnesium surface can be strengthened by using the existing Al-Si alloys.
