Tensile behaviour of aluminium 7017 alloy at various temperatures and strain rates

The objective of the present study is to carry out high strain rate tensile tests on 7017 aluminium alloy under different strain rates ranging from 0.01, 500, 1000 and 1500s(-1) and at temperatures of 25, 100, 200 and 300 degrees C. Quasi-Static tensile stress-strain curves were generated using INSTRON 8500 machine. Johnson-Cook (J-C) constitutive model was developed for 7017 aluminium alloy based on high strain rate tensile data generated from split Hopkinson tension bar (SHTB) at various temperatures. This study evidently showed an improvement in dynamic strength as the strain rate increases. The predictions of J-C model are observed to be in consistence with the experimental data for all strain rates and temperatures. The fracture surfaces of specimens tested were studied under SEM. The change in fracture mode has been observed at different strain rates. The shear mode of fracture is dominant at lower strain rates (0.01 and 500s(-1)); whereas cup- and cone-like surface representing dimple structure is found at the higher strain rates (1000 and 1500s(-1)). The numbers of dimples at high strain rates are more than the quasi-static and intermediate strain rates. It is also observed that the flow stress decreases with increase in temperature. The 7017 aluminium alloy demonstrates thermal softening at higher temperatures. So when the temperature is more than 200 degrees C at these strain rates, thermal softening is predominant mode of deformation mechanism. It is found that when the temperature increases to 200 degrees C, the number of dimples rises and the dimple size of 7017 aluminium alloy is larger than at lower temperatures. (C) 2015 Brazilian Metallurgical, Materials and Mining Association. Published by Elsevier Editora Ltda.