Abstract
By means of Vickers-hardness and electrical conductivity measurements, DSC tests and TEM analyses, the effect of different pre-aging treatments on precipitation characteristic of the Al-1.29Mg-1.22Si-0.68Cu-0.69Mn-0.3Fe-0.2Fe-0.1Ti (mass fraction, %) alloy during subsequent artificial aging was investigated. The results indicate that with increasing pre-aging time from 2.5 min to 10 min at 170 °C, the number of formed β” nuclei increases, resulting in promoting artificial aging kinetics and enhancing peak hardness. The hardness of pre-aged alloy reduces within lower temperature range of non-isothermal aging and increases in early stage of isothermal aging at 170 °C. The size and density of clusters in pre-aged samples determine the hardenability in early stage of artificial aging. Pre-aging has dual mechanisms: namely, clusters (β” nuclei) formed by pre-aging can inhibit the precipitation of GP zones during natural aging, and can quicken the precipitation of β” phase in the early stage of subsequent artificial aging.
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