Mechanical Property and Precipitation Behavior in Al-Mg-Si-Cr-Be-(Mn) Alloys for Auto Body Materials

摘要

Al-Mg-Si base alloys have a good strength,formability, corrosion resistance and bake hardenability. Butthe bake hardenability of Al-Mg-Si-Cr-Be alloy is better thanthat of Al-Mg-Si alloy. Mn is added to improve the toughnessin Al-Mg-Si alloys. But the precipitation behavior of Al-Mg-Sibased alloys with large amount of Mn addition(>0.5 wt percent)has not been reported yet. Therefore, the mechanical propertyand precipitation behavior of the Al-Mg-Si-Cr-Be alloy with0.5-l.5 percent Mn was observed using the hardness and tensiletests, differential scanning calorimetry (DSC) and transmissionelectron microscope(TEM). The tensile strength of Al-Mg-Si-Cr-Be alloy increased with the increase of Mn content withoutdecrease of elongation due to the increase of Mn dispersoid.Therefore, the combination of properties such as strength andductility in the Al-Mg-Si-Cr-Be-Mn alloy was better than thatin the Al-Mg-Si-Cr-Be alloy. The formation energy of #beta#"phase of Al-Mg-Si-Cr-Be alloy is decreased by the addition ofMn. But The precipitation of #beta#' phase of Al-Mg-Si-Cr-Bealloy is little affected by the addition of Mn.