Formation, Thermal Stability and Mechanical Properties of Cu-Zr-Al Bulk Glassy Alloys

抄録

New Cu-based bulk glassy alloys with large supercooled liquid region and high mechanical strength were found to be formed in Cu–Zr–Al ternary system. The large supercooled liquid region exceeding 70 K was obtained in the composition range of 40 at%Zr at 2.5 at%Al, 37.5%Zr to 47.5%Zr at 5%Al and 42.5%Zr at 7.5%Al. The largest ΔT_x was 74 K for Cu₅₅Zr₄₀Al₅ and Cu₅₀Zr_42.5Al_7.5 alloys and the highest T_g⁄T_l was 0.62 for the former alloy. The alloys with large ΔT_x values above 70 K were formed into a bulk glassy rod form with diameters up to 3 mm by copper mold casting and the glassy alloy rods exhibit high compressive strength of 1885 to 2210 MPa and Young’s modulus of 102 to 115 GPa combined with elastic elongation of 1.60 to 1.95% and plastic elongation of 0 to 0.4%. The addition of 2.5 to 7.5%Al to Cu–Zr alloys was very effective for the increase in glass-forming ability as well as the stabilization of supercooled liquid. The effectiveness can be interpreted on the basis of the concept of the formation of the unique glassy structure in special multi-component alloys with the three empirical component rules.