Deformation Behaviour of Al-5%Si Alloy at High Temperatures and Different Strain Rates

The constitutive behaviour of Al-5% Si alloy has been studied in the temperature range 500–800 K and in the strain rate range 0.02–200 s⁻¹ in view of obtaining flow stress data and evaluating the mechanism of hot deformation. For this purpose, hot compression tests have been conducted on cylindrical specimens of the alloy. From the transient measurements of force, ram travel and temperature changes during deformation, the values of flow stress, true strain and strain rate have been calculated. The kinetics of deformation has been described using standard kinetic rate equations. An apparent activation energy of 130 kJ/mol and an apparent activation volume in the range 10–200 b³ have been evaluated from the temperature and strain rate dependences of flow stress. It is suggested that at high temperatures and strain rates, the deformation takes place by cross-slip of screw dislocations.