Al-5.5Mg-1.5Li-0.5Zn-0.07Sc-0.07Zr alloy produced by gravity casting and heat treatment processing

摘要

Al-5.5Mg-1.5Li-0.5Zn-0.07Sc-0.07Zr alloy was produced by gravity casting and heat treatment processing. After gravity casting based on the melting processing scheme designed specifically for the studied alloy, there was no obvious porosity and slag. In as-cast alloy, there were many network-shaped second phase particles enriched along the grain boundaries, most of which integrated into the -Al matrix after solution heat treated at 500 degrees C for 10h. The grain growth was inconspicuous, which means low grain boundary stress concentration resulted by planar slip. To meet the requirement for industrial actuality, avoid the excessively detrimental effect of PFZs and utilize the order hardening effect of (Al3Li) phases sufficiently, 175 degrees C/8h was preferred as the aging regime. Optimal comprehensive mechanical properties were obtained after solid solution heat treated process (500 degrees C/10h) and subsequent aging treatment (175 degrees C/8h) with elongation, yield strength, and ultimate tensile strength reaching 8.7%, 270.5MPa, and 435.5MPa, respectively.