Product microstructures and properties induced by hot working a Pb-1.85 Pct Sb alloy
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INTRODUCTION
LEAD-antimony alloys are suitable for many engineering applications such as radiation protectors, noise barriers, and, most importantly, for the manufacture of grids of leadacid batteries. High antimony contents of about l 1 pct (the eutectic composition) give the alloy sufficient strength and good castability, but also lead to corrosion problems, particularly in battery applications. Solubility at the eutectic temperature of 252 ~ is 3.45 pct Sb.~ Decreasing the antimony content to below 3 pct reduces corrosion but introduces some other problems, including hot tearing during casting, an increased tendency toward microporosity, and low strength. These problems can be reduced by hot working the as-cast alloy. The combined deformation and thermal processing of the wrought alloy can be expected to improve greatly the integrity of the structure and to enhance the mechanical properties of the product. There are few published studies of the effects of hot working on Pb-Sb alloys. Tilman et al.2'3 subjected lead alloys containing up to 5 wt pct Sb to a multipass rolling schedule at 125 ~ and 175 ~ with reheating between passes for 15 minutes. Both creep resistance and tensile strength improved in comparison to conventionally cold rolled alloys. Optical micrographs of the hot-worked alloys revealed the existence of a dislocation substructure. Borchers and Reuleaux 4 applied a treatment comprising solution annealing for 24 hours at 240 ~ quenching in ice water, reheating to 240 ~ and deforming by single-stage upsetting to 50 pct (e = 0.7) at a rate of 0.5 mm per second (k ~ 3 x 10-3 s-!). Holding at the deformation temperature for 30 minutes induced recrystallization; the samples were then quenched again in ice water. This study showed that deformation at solid-solution temperatures yields finer-grained structures than solution treatment of an undeformed material. However, keeping the material at deformation temperature for 30 minutes eliminated any substructure that may have formed during deformation. A. SHERIF EL-GIZAWY is Assistant Professor, Department of Manufacturing, Bradley University, Peoria, IL 61625. JOHN A. SCHEY is Professor, Department of Mechanical Engineering, University of Waterloo, Waterloo, ON N2L 3G1, Canada. Manuscript submitted April 16, 1984.
METALLURGICAL TRANSACTIONS A
It is evident from past research that thermomechanical working can be used to change the structure and properties of low-antimony lead alloys. However, no data were available on the effects of hot working parameters such as temperature and rate of deformation, and the present work addressed this question with special emphasis on the influence of deformation on precipitation behavior. In this respect, two cases need to be considered: first, deforming the alloy while it is in the solid-solution regime and, second, deforming while the solute elements are in the form of second-phase dispersed particles. It is generally known that lattice defects introduced either prior or during aging can greatly affect both the kineti
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