Precipitate coarsening and mechanical properties in 6082 aluminium alloy during long-term thermal exposure

Abstract

Long-term thermal stability is essential for the use of 6082 aluminium alloy in battery packaging. Precipitate coarsening and property changes in the alloy during 1000 h of thermal exposure at 100, 125, 150, and 175 °C were studied experimentally and theoretically. Variations of tensile properties were exhibited. The microstructural and nanoscale precipitates were characterized by microscopy (OM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Alloys exposed at 100 °C and 125 °C were thermally stable, retaining the strength above 340 MPa after a thermal exposure of 1000 h. Alloys exposed at 150 and 175 °C lost 25% and 48% of their respective strengths after 1000 h of exposure, reaching 253 and 178 MPa. Precipitates gradually increase in size with increasing thermal exposure time or temperature, while their number density decreases. After thermal exposure at 175 °C for 1000 h, the length of precipitates increased from 31 nm to 328 nm, and the coarsening rate of precipitates was 2.22 × 10−30 m3s−1. Comparing the experimental and theoretical coarsening rates showed that the Kuehmann–Voorhees (KV) model is suitable for calculating the precipitate coarsening rate of 6082 aluminium alloy. This study proposes a new method to predict the strength of aluminium alloy after thermal exposure; the effect of precipitate coarsening on alloy properties is also discussed quantitatively.