Characterization of Hot Deformation of CW602N Brass

Abstract

Alpha brasses (in principle single-phase solid solution alloys containing less than 35% Zn) are usually processed by extrusion, forging or rolling. Although these materials are of widespread use, few detailed studies of the ow behavior of brass at high temperature are available. The hot workability of a CW602N brass (Cu36.5%Zn2%Pb) was thus investigated by torsion testing in the temperature range between 550 and 800• C, under equivalent strain rates ranging from 0.01 to 10 s −1 . The peak ow stress dependence on temperature and strain rate was described by the well-known Garofalo equation, with a stress exponent close to 4 and Q =220 kJ mol −1 . A considerably larger scatter of the experimental data was observed in the high temperature range. The detailed microstructural analysis of the deformed samples by scanning electron microscopy revealed substantial dierences among the samples deformed in the low temperature regime and those torsioned at 750 and 800• C. These dierences were analyzed and discussed to rationalize the dierent mechanical responses observed in the two hot-deformation regimes.

The Search for Reliable Inputs in Modelling Hot Working Operations: A Model Describing the Flow Behavior of Metals at High Temperature Applied to CW602N Brass

“…Figure 4 shows that for 0 < ε < 2, Q HW decreases from 242 to 225 kJ/mol, in good agreement with the average value of 220 kJ/mol obtained by calculating the strain rate dependence of peak ow stress [12]. On the other hand, the microstructural analysis of the deformed Fig.…”

“…Variation of QHW and A3, from equation (10), as a function of strain. Comparison between experimental and calculated values of the peak ow stress; the latter were obtained by identifying the maximum in the model curves given by Equation (3), with the parameters reported in the Table. samples (illustrated in [12]) clearly indicated that the microstructure of this material is predominantly composed by the α solid solution of Zn in Cu, with minor but not negligible (510% in volume) presence of β bcc-phase. Since the β-volume fraction increases with temperature, the calculation of Q HW is signicantly aected by the progressive precipitation of this softer phase.…”

A Comprehensive CFD Model for Dual-Phase Brass Indirect Extrusion Based on Constitutive Laws: Assessment of Hot-Zone Formation and Failure Prognosis

“…ε is the equivalent strain rate, Q (J/mol) is the activation energy, R (J/(molK)) is the universal gas constant and T (K) is the absolute temperature. The parameters of Equations (18) and (19) are usually derived from hot torsion experiments with variable temperature and torsion speed [18][19][20][21][22]. By substituting (19) in (18) and solving for σ p , we acquire the plastic stress that is used in (3):…”

“…We use Equation (21) in the simulations, with σ p,α and σ p,β that correspond to the plastic stresses of α-brass CuZn36 and β-brass CuZn44, respectively. Each individual plastic stress is computed by (20) using the parameters in Table 1 (reported in [19]). The use of a mixing law is essential, because at the process temperature (715 • C) and according to (21), the α-phase is three to four times harder (depending to the strain rate) than the β-phase.…”

“…The presence of critical production defects, associated with extrusion abnormalities, could affect acutely the life expectancy of critical parts and compromise the reliability and safety of installations and machine operation during their service time. The brass extrusion process, using material constitutive models, has been already studied [18][19][20]. However, the comprehensive investigation of the indirect extrusion process of dual-phase brass alloys, combining the utilization of a CFD numerical model and constitutive equations (Zener-Hollomon type), in the frame of featuring and predicting potential defects or failures during production, through visualization of flow pattern and temperature distribution is a novel and original approach which has not been published elsewhere according to the best of our knowledge.…”