Effect of Ag addition on the glass-forming ability of Mg-Cu-Y metallic glass alloys

The effect of Ag substitution for Cu on the glass forming ability was studied in Mg₆₅Cu_25-xAg_xY₁₀ (x = 0, 5, 10, 15, 20, 25) alloys by using thermal analysis and X-ray diffractometry (XRD). With increasing x from 0-25, the glass transition temperature, T_g, of melt spun Mg₆₅Cu_25-xAg_xY₁₀ alloys increases slightly from 426 to 436 K, and the crystallization temperature, T_x, decreases from 494 to 459 K, resulting in a decrease in the supercooled liquid region. However, a partial substitution of Cu by Ag in Mg₆₅Cu₂₅Y₁₀ promotes the glass formation. The maximum diameter for amorphous phase formation by injection casting increases from 4 mm in Mg₆₅Cu₂₅Y₁₀ to 6 mm in Mg₆₅Cu₁₅Ag₁₀Y₁₀ alloy. Both amorphous Mg₆₅Cu₁₅Ag₁₀Y₁₀ alloys prepared by melt spinning and injection casting showed similar crystallization process during continuous heating in differential scanning calorimetry (DSC). The relationship between the critical diameter for the formation of an amorphous phase in injection casting and the parameters reflecting glass-forming ability was examined.