Process model for strength of age hardenable aluminium alloy welds

An existing process model for hardness prediction in age hardenable aluminium alloy welds is presented and analysed. One of the key criticisms of this model is that its derivation assumes softening is due to precipitate dissolution alone. The influence of precipitate coarsening has been determined by developing an equivalent model for softening owing to coarsening. It is shown that the experimentally derived master curves that form the basis of the model are capable of representing softening by a mixture of precipitate coarsening and dissolution. Methods to predict post-weld natural aging are discussed, and a new method is presented based on direct prediction of the Guinier-Preston zone fraction. The model has been applied to friction stir welding. Model predictions agree well with measured hardness profiles, and the sensitivity of the predictions to temperature is discussed. © 2006 Institute of Materials, Minerals and Mining.