Influence of PVD Target Power on the Age Hardening Behaviour of Al-4Zr Micro Sheets

Abstract

High strength aluminium alloys with improved stability at elevated temperatures for micro components, which are needed e.g. in the automotive or the micro electronics industry, require new alloys and advanced production processes regarding primary shaping, heat treatment and cold forming. Their development is part of the Collaborative Research Centre 747 Micro Cold Forming of the German Research Foundation. Especially heat treatment is a necessary step in the manufacturing process chain to adjust the mechanical properties of semi-finished micro components to cold forming and finally the usage properties of aluminium micro components by precipitation hardening to increase the strength above the strain hardened level. Conventional casting techniques limit the dissolvable zirconium content in alloys to 0.28 mass-% due to Al3Zr precipitation of higher contents during slow cooling. With physical vapour deposition (PVD) by magnetron sputtering at temperatures below 50 °C it is possible to achieve alloys with a highly oversaturated solid solution and up to 3.6 mass-% of zirconium. The target power of the plasma during the magnetron sputtering process has considerable impact on the mechanical properties of the deposited Al-Zr alloys. Therefore the age hardening response of different micro sheets is evaluated by ultra micro hardness measurements (UMH), transmission electron microscopy (TEM) and differential power scanning calorimetry (DPSC).