Evaluation of hot and warm forming of age-hardenable aluminium alloys into manufacturing of automotive safety critical parts

Abstract

Lightweight solutions will become increasingly necessary for the next generation of passenger cars. Applications of age-hardenable high strength aluminium material can be superior to traditional low strength alloys, especially if the processing of the parts itself is cost effective. Sheet forming of aluminium at elevated temperatures has been addressed in the current work. Warm forming directly after solution heat treatment can eliminate several process steps and reduce cycle time in the production of light weight load bearing car components. However, this is not straight forward as 6xxx alloys need minimum critical cooling rate to achieve the full potential of precipitation hardening. The technical forming methods must take this into the thermomechanical setup during the process steps of handling, lubrication, deformation, and final ageing. Elevated forming temperatures, more likely warm than hot show high formability of the alloys. Further, a short artificial ageing time demonstrate required strength and fatigue capacity in real components. Reduction of the deformation temperature to below 300°C is still favourable when lubrication for serial production is the issue. The modified thermomechanical method is appropriate for achieving accurate geometrical tolerances, uniform properties, and high productivity for aluminium automotive parts. The paper describes a feasibility study and method development for forming of sheet material of hardenable aluminium alloys at intermediate temperatures.