Effect of predeformation on microstructure and tensile properties of Al-Mg-Si alloys with high silicon content

The effect of predeformation on the microstructure and tensile properties of two Al-Mg-Si alloys with high excess Si has been studied by tensile testing and TEM analysis. The results show that the strength of Al-Mg-Si alloys in the underaged condition is greatly increased by prestretching immediately after water quenching. Both the deformation strengthening and the extra precipitation strengthening play important roles in providing the increase in strength. Precipitates of beta" are observed to form directly on dislocations with a larger size than those that form in dislocation free areas When the prestretching is less than 5%, the increase in predeformation results in an increase in beta" precipitate density, whereas prestretching by 10% leads to larger size but lower density of beta" precipitates.