High temperature processing of brass: Constitutive analysis of hot working of Cu-Zn alloys

The hot workability of CW602N brass, containing 36.5% Zn and 2% Pb, was investigated in the present study by hot torsion tests carried out between 550 and 700 °C. A detailed analysis of the literature data was preliminarily aimed at developing a constitutive model able to describe the hot deformation of single-phase α-brasses. The model, based on the Garofalo sinh equation, gave excellent descriptions of the mechanical response of copper alloys containing Zn amounts ranging from 0% to 30%, but overestimated the strength of the CW602N at the highest temperature. The model was then combined with the law of mixtures, to take into account the presence of the soft β-phase, that appears when the Zn content increases above 35%, as was indeed observed in the CW602N. Both the flow curves and the peak flow stress dependence on strain rate were successfully modeled by assuming that the microstructure was composed of hard α-grains and soft β-grains, containing Zn amounts close to 36-37% and 42-44% respectively.