Evaluation of Microstructure and Mechanical Properties of 5182 Aluminum Alloy Ingots with Large-Sections

The microstructure and mechanical properties of continuously-cast 5182 aluminum alloy ingots with large-sections are not uniform，which depends on the diameter of ingots and the position where the sample locates. For the Φ160 ingot, the outer layer and middle layer have fine and uniform α-Al grains, while the centre appears the coarse α-Al dendrite. In contrary, the middle and centre layers appear the coarse α-Al dendrite, only the outer layer has the fine α-Al grains for the Φ380 ingot. The (FeMn)Al6 and Mg2Si phases coexist in the primary α-Al grain boundaries and the Mg2Al3 phases precipitate in the α-Al grains. By homogenously annealing, the Mg2Si and (FeMn)Al6 phases are broken-up into dispersive islands and particles and the Mg2Al3 phases precipitate more sufficiently in the forms of fine particles and short flakes. The elongation is largely enhanced; while the yield strength, tensile strength and hardness receive much less influence by the heat treatment. However, the homogenous annealing at 495 oC for 24 h is not enough for adjusting the microstructure of the Φ380 ingot.