Advances on the optimization of the thermal treatment and modelization on the multi-stage wire drawing process with ZnAl15% alloy wires

Abstract

This study establishes a thermo-mechanical processing framework for design and optimization of the ZnAl15% multi-stage wire drawing by controlled heat treatment, constitutive behaviour modelling and analytical/finite element modelling (FEM). The work prioritizes (i) tuning pre-drawing microstructure for optimal ductilitystrength balance, (ii) formulating a strain-rate dependent flow model incorporating DRV induced by partial recrystallization (DRX), and (iii) quantification of drawing load, friction, and temperature evolution to ensure process stability and dimensional integrity. Best alloy condition was achieved by heat treating at 233 ◦C (1 h ramp + 2 h hold + 24 h slow cooling), improving tensile strength and elongation capacity while maintaining ductility. The alloy exhibited mild strain-rate sensitivity (m = 0.0225, K = 246.99 MPa). During six drawing passes, DRV affected the mechanical response leading to elongation of the primary grains and an approximately 16% reduction in microhardness (from 62 to 52.2 HV0.3). The yield strength and ultimate tensile strength decreased by about 18–20%, while the elongation at break was reduced by roughly 30–60%. These results indicate that the alloy undergoes work softening induced by the sequential forming process. The die/wire friction coefficient was established between µ = 0.18÷0.29 in the wire-die interface. Modelled drawing stresses agreed well with experiments showing < 6% deviation with respect validation experiment. Measured exit temperatures (26–36 ◦C) and predicted equilibrium values (45–61 ◦C at 1.27 mm from the die cone) confirmed consistent thermal behavior, while FEM revealed localized deformation-zone temperatures > 100 ◦C, sufficient to trigger DRV. ZnAl15% wire drawing can be robustly modelled integrating strain hardening and DRV effect due to worksoftening (WS). The integrated methodology constitutes a reliable framework for industrial process design and optimization.