| Aluminum-lithium alloys, by virtue of their high strength-to-weight ratio, serve as an attractive alternative to conventional aluminum alloys, despite higher production costs. Some problems, like low fracture toughness and anisotropy are associated with these alloys.; A semi-empirical process model for describing the precipitation hardening behaviour of AA8090 was constructed and validated by comparing with experimental ageing data. Ageing experiments were carried out to generate the experimental ageing curves. The unknown constants were then calibrated using the experimental ageing curves. The next step was the definition of two parameters, the kinetic strength P and the peak precipitation strength, S{dollar}sb0{dollar}, which were useful in the synthesis of all the equations.; The results of this study show that the fit between theory and experiment is quite good. The model satisfactorily describes the ageing behaviour of the 8090 alloy. This modelling technique, however, is for the 8090 system alone although the approach could be used to model other precipitation hardenable systems.; A different and more useful method (the Time-Temperature-Hardness diagram) of presenting ageing data has also been described. A methodology for application of this technique to model reheating behaviour and non-isothermal heat treatment has been outlined. (Abstract shortened by UMI.)... |
