Room-temperature mechanical behavior of cryomilled al alloys

摘要

Room-temperature mechanical properties of cryomilled Al-7.5 pct Mg and Al 5083 alloys are discussed in the context of a duplex microstructure, which arises during processing. After consolidation via hot isostatic pressing (“hipping”), coarse-grained regions are formed in former interparticle void volumes, and these regions become elongated during extrusion. Comparison of tensile and compression testing results on both “as-hipped” and extruded materials shows that tension-compression asymmetry is the result of these coarse-grained regions and not necessarily a fundamental property of ultrafine grained Al. The strength of the extruded materials is consistent with the Hall-Petch model of strengthening by grain size refinement, but the hipped material deviates from this trend, with a lower strength despite finer average grain size. This can also be attributed to the presence of coarse-grained regions, which substract from the strength in a predictable manner and also enhance the ability of the cryomilled material to work harden.