Enhancement of strength mechanical and corrosion resistance of 7055 alloy with minor Sc and Y addition

Abstract

A new type of 7055-Y-Sc alloy with high strength and corrosion resistance was prepared. Eutectic Al _3 Y particles with sizes in the range of 500–600 nm were found in the as-cast structure of the 7055-Y-Sc alloys. The addition of Y significantly accelerated the precipitation of Al _3 Zr with L1 _2 structure in Al–Zr–Y alloy, and the number density of Al _3 (Zr, Y) precipitates was almost a grade higher than that of Al _3 Zr. In the process of aging at 120 ℃/12 h, the nano scale L1 _2 -type Al _3 (Sc _x Y _y ) phase nucleated uniformly within the Al matrix and nonuniformly on the dislocation. The grain size decreased from 100–200 um in 7055-Y-0Sc to 40–50 um in 7055-Y-0.25Sc, the percentage of Sc continued to increase, and the grain size remained unchanged or even increased, thereby decreasing the Vickers hardness of 7055-Y-Sc alloys from 196.4 HV to 187.9 HV. After aging, the hardness and tensile properties of 7055-Y-Sc alloy showed good performance. The effective Sc proportion of the 7055-Y-Sc alloy was 0.25%. Its tensile strength was 398.6 MPa. Its conductivity was 33.8% IACS. The current corrosion density was 6.7 × 10 ^−8 A cm ^−2 , its good strength, corrosion resistance and conductivity make the studied alloy to be a promising material.

Keywords

• 7055 alloy
• scandium
• yttrium
• Al3Y
• Al3 (Scx Yy)
• tensile properties