SUPERPLASTIC FLOW AND FAILURE AT 773 K IN THE ALUMINIUM - CALCIUM EUTECTIC
The superplastic behaviour of the hot rolled Al - Ca eutectic alloy (7.6wt % Ca) was investigated at a temperature, T=773K, with strain rates varying from 2 x 10**-5 to 4 x 10**-1 sec**-1 and for a grain size of the order of 3 mum. The results showed that the stress strain rate behaviour could be divided into two distinct portions: (a) region II at intermediate and low strain rates the strain rate sensitivity index, m, was >=0.30 (superplastic regime); (b) region III at higher strain rates (DOT OVER epsilon > 4 x 10**-2 sec**-1) where m was < 0.30 (conventional deformation regime). Elongations at fracture of greater than 300 % were achieved on the region II of superplasticity (maximum value about 570 %). There was experimental evidence in superplastic flow conditions of a grain boundary sliding process and dislocation activity within the aluminium matrix grains. The fracture depended on a void linkage mechanism which included on a microscopic scale the internal necking of the tiny ligaments already formed between the cavities.
Bibliographic Reference: JOURNAL OF MATERIALS SCIENCE, VOL. 18 (1983), PP. 2471-2483
Record Number: 1989122060400 / Last updated on: 1987-01-01
Available languages: en