Deformation behavior and processing map of ATI 425 with initial lamellar microstructure

Abstract

The effect of hot compression temperatures and strain rates on deformation behavior and resultant microstructure of ATI 425 alloy with initial lamellar microstructure was investigated in this study. The temperature and strain rate of the hot compression test were chosen to be in the 700-1100 °C and 0.001-1 s-1 ranges, respectively. The stress-strain curve and microstructure evaluation show that the alloy's flow softening is associated with globularization and dynamic recrystallization mechanisms. The constitutive equation calculates the activation energy for the α/β and β regions to be 348 kJ/mol and 201 kJ/mol, respectively. Dynamic recovery and partial recrystallization are the dominant structure modification mechanisms in the beta single-phase region. Bending and fragmentation of alpha plates is the dominant mechanism of microstructure promotion in the α/β region at low temperatures and low strain rates, less than 0.1s-1. Local shear and alpha plate break-up are the main factors in structural modification at high strain rates, greater than 0.1s-1. The extracted process map at 0.5 strain revealed three zones: instability, safe zone, and peak zone, with power dissipation efficiencies of 0 -0.25%, 30-40%, and above 40%.

Keywords

• ati425 alloy; lamellar microstructure; dynamic recrystallization; bending and fragmentation; processing map.