Superplastic behaviour of a rapidly solidified 7475 aluminium alloy

To investigate possible superplastic behaviour, tensile tests were performed on conventionally cast and extruded aluminium alloy AA 7475, rapidly solidified and extruded AA 7475, and rapidly solidified and extruded AA 7475, which contained 0.45 wt%. Zr. The rapid solidification process used was melt spinning. The extruded materials were not subjected to thermomechanical processing, but the effects of various simple heat treatments were investigated. The rapidly solidified Zr-containing alloy had the smallest grain size (1 μm), the highest elongation, and the lowest flow stress. Heating at 300 °C for 4 h improved the elongation and lowered the flow stress for this alloy. After this treatment, an elongation of 390% was observed at 450 °C and a strain rate of 8 × 10−2 s−1. The strain rate sensitivity exponent was 0.58. It was concluded that the rapidly solidified Zr-containing alloy was superplastic and that a full thermomechanical treatment after rapid solidification is not needed to achieve such an effect.