Investigation Of Mg-Zn Based Amorphous Alloys And Their Composites

Mg based amorphous alloys are regarded as a new family of the promising structural materials for their high strength and low density.Generally,multi-component system shows good glass forming ability(GFA) which has the characters of large atomic size mismatch and negative mixing heat amongst the constituent elements.At present, increasing attention is paid to the amorphous phase reinforced matrix composites materials due to their combined mechanical properties of both amorphous alloy and crystal alloy.In this paper,Mg-Zn based amorphous alloys and their comosites were prepared by copper mould casting.The microstructures and phase constituent were analyzed by scanning electron microscopy(SEM) and X-ray diffraction(XRD).The mechanical of bhe bulk metallic glass composites were tested by universal electronic material testing machine. The microstructure,mechanical property,glass forming ability and phase constituent how to effect the mechanical property were investigated by means of the measurement of the strain-stress curves,phase ascertain and microstructure observation.Mg_72-xZn₂₈Ca_x(x=1～6) alloys were fabricated.The results show that the GFA is improved with the increasing of Ca content.The GFA of Mg₆₈Zn₂₈Ca₄ alloy is the best among the alloys,which has the plasticity of 6.2%.Mg₈₀Zn_16-xCa₄Y_x(x=2,4 and 6) alloys were prepared.The results show that these alloys are amorphous matrix composites.The relatively better composition is expressed as Mg₈₀Zn₁₂Ca4Y₄ which exhibits the largest strain up to 11.5%and stress of 680MPa respectively.Mg₈₀Zn_16-xCa₄Al_x(x=2,4 and 6) alloys,Mg₈₀Zn_16-xCa₄Ni_x(X=2,4 and 6) alloys and Mg₈₀Zn_16-xCa₄Cu_x(x=2,4,6) alloys were prepared.The reason why those alloys reached so high compressive strenth is because of the dispersed precipitates in the matrix.Mg₅₇Cu_33-xNd₁₀Ag_x(x=0,2.5,5 and 7.5) were fabricated and the result shows that the Ag can improve the GFA of the alloys,which has the best content of 2.5 at.%.