High-precision dilatometry as novel tool for in-situ real-time monitoring of aging processes in Al alloysTuesday (27.09.2016) 11:00 - 11:15 Part of:
A detailed understanding of the atomistic processes governing the age hardening response of aluminum alloys is of vital importance for optimization of their properties. Many industrial alloys exhibit a highly complicated precipitation sequence which often is not understood in all its details. While a static characterization of metastable precipitates is possible by advanced microscopic techniques, e.g., TEM analysis, the kinetic aspects of phase formation are much more difficult to assess. Since in general a phase formation or dissolution process is accompanied by a volume change, dilatometry would in principle be the method of choice for the characterization of such phenomena. However, the resolution limit of most commercially available devices especially in isothermal measurements is limited to the (Delta L)/L = 10^(-4) regime, which can be insufficient to resolve the details of a phase formation sequence. In this work we present isothermal high-precision length-change measurements during artificial aging of a commercial AW6060 alloy sample at different temperatures. The measurements were performed in a laser dilatometer with major parts being self-desigend, which allows for high-stability investigations on time scales of up to 10^6 s with a resolution limit better than (Delta L)/L = 1×10^(-5). The results support the proposed precipitation sequence for Al-Mg-Si alloys and clearly show the transitions between the different steps towards the stable Mg2Si phase.