Hot working analysis of a CuZn40Pb2 brass on the monophasic (β) and intercritical (α+β) regions

Abstract

The high temperature deformation behavior of a Cu40Zn2Pb brass was studied by means of compression and tensile tests in the β monophasic and α/β biphasic regions. The ductility evaluated in terms of elongation and area reduction allowed to distinguish three regions: one β monophasic region (above 720°C), and two α/β biphasic regions, between 720°C and 600°C, and below 600°C. The fracture appearance was evolving from a ductile type, with dimple formation, to a more brittle one with grain decohesion as the deformation temperature was decreased or the amount of β phase reduced.The “apparent” creep exponent values for the peak and steady stresses were close to 4 and 3, respectively, indicating that the glide and climb of dislocations and grain boundary sliding were the main controlling deformation mechanism, respectively. On the other hand the “apparent” activation energy values for the peak and steady stresses were 268.83±11.64 and 254.9±20.62kJ/mol, respectively, being all well above the self-diffusion activation energy values of either Cu (197kJ/mol) or Zn (91.7kJ/mol).The modeling of the flow curves was carried out by physically-based constitutive equations considering the coexistence of recovery, work hardening and recrystallization on a two-phase material. The β phase, rich in Zn, enhanced the dynamic recovery and retarded the recrystallization kinetics, while the opposite was determined for the α phase, rich in Cu.