A Superplastic Al-Li-Cu-Mg-Zr Powder Alloy with High Hardness and Modulus

Structure/property studies were made on an experimental Al-3.18% Li-4.29% Cu-1.17% Mg-0.18% Zr powder alloy, which is of the low density/high modulus type. Alloy powder was made by the P&W/GPD rapid solidification rate (RSR) process, canned, and extruded to bar. The density was 2.458 × 106 g/m3. The material was solution-treated, and aged at 149°C (300°F), 171°C (340°F), and 193°C (380°F), using hardness tests to determine the aging curves. Testpieces solution-treated at 516°C (961°F) showed an average yield strength (0.2% offset) of 43.3 ksi (299 MPa) and ultimate tensile strength of 50.0 ksi (345 MPa), with 1% elongation, which increased to 73.0 ksi (503 MPa) and 73.1 ksi (504 MPa), respectively, with only 0.2% elongation, on peak aging at 193°C (380°F), with a modulus of elasticity of 11.4 × 106 psi (78.3 GPa). Hardness values reached 90–92 RB on aging at 149–193°C (300–380°F). The as-extruded alloy showed superplastic behavior at 400–500°C (752–932°F) with elongations of 80–185% on 25.6 mm, peaking at 450°C (842°F). An RSR Al-2.53% Li-2.82% Mn-0.02% Zr extruded alloy showed only 18–23% elongation at 400–500°C (752–932°F).