Influence of microstructure on the subzero temperature tensile properties of heat treated AA7010 plates

摘要

The influence of variation in test temperature i.e. ambient and subzero (-50°C) on the tensile properties of aluminium alloy 7010 plates, heat treated to varying aging conditions (i.e. naturally aged, under aged, peak aged and over aged), have been examined. It is shown that the maximum increase in strength properties (both yield and ultimate tensile strengths) upon changing the test temperature from ambient to subzero is obtained in the case of naturally aged samples. Whilst, there is a minimal increase in the strength properties of the under aged samples when tested at -50°C. These results are discussed in light of changes in the work hardening behaviour of the materials with aging. It is further observed, irrespective of the test temperature, that there is a distinct change in the mode of fracture on tensile loading from a combination of predominantly shear together with partial ductile dimple fracture in the naturally aged samples to predominantly ductile dimple fracture in the over aged samples. This is correlated with the significant increase in the number density of void nucleating precipitates with artificial aging.