| Popis: |
The production of high performance forging parts can be achieved by the use of agehardening aluminium alloys in combination with deformation, temperature and heat treatment. Forging or impact extrusion can be carried out at elevated temperatures to improve formability and to reduce the need of forming pressure. There is a good indication that forming in warm condition in as-quenched temper (W) followed by artificial ageing gives improved product properties, lower tooling pressure and a possibility for cost effective processing. The deformation hardening mechanism in combination with precipitation mechanism is not well understood, and these effects are not necessarily additive with respect to strength. The interaction between dislocations, vacancies and formation or the stability of GP-zones is a key mechanism in the age hardening alloys deformed in temper W, ref. Howard [7] and Latkowski [8]. The deformation in the warm temperature region, moderately hot, gives interesting possibilities to reduce forging pressure and still has the ability to age harden the alloy. The present investigation is based on two standard alloys AlMgSi and AlZnMg, both from serial production. The not recrystallized microstructure obtained by the combined deformation-precipitation process reveals the improved fatigue strength that is promising in comparison with the traditional separate deformation heat-treatment processing, with references to Pedersen [1] and [2]. |
