Study of the Hot Workability of Al-8.5 Wt Pct Mg Alloys for Armor Plate Applications

摘要

Hot-torsion tests were conducted to examine the hot workability of standard and enhanced purity A1-8.5 wt% Mg ingots in both the as-cast and homogenized conditions. The enhanced purity variant showed substantially higher hot ductilities at all homogenization and deformation temperatures investigated with no change in equivalent tensile flow stress. The optimum homogenization practice consists of two stages, namely stage-1 for >5 h at 427 C (800 F) plus >6 h at 482 C (900 F) which provides an equivalent tensile strain-to-failure of approximately 3 as opposed to 1 in the as-cast condition at a strain rate of 0.1 s-1. The optimal strain rate for hot working this A1-8.5 wt% Mg alloy is considerably lower than the nominal 1.2 s-1 typically used in commercial practice for many other Al-Mg alloys. In particular, a strain rate between approximately 0.1 and 0.01 s-1 gives the highest measured strain-to-failure for the alloys containing 0 and 2 ppm sodium. High strain rates and/or higher deformation temperatures promote a brittle quasi-cleavage fracture morphology that reflects the alloy's low ductility under these normal commercial hot-working conditions. A rolling trial using laboratory-scale ingots was successfully conducted with minimal edge cracking using the parameters determined from the hot-torsion tests. Keywords: Rolling metallurgy; Aluminum; Magnesium; Armor plate; Aluminum alloys. (kt)