Unraveling the effect of trace sulfur content on hot working behavior of Cu-DHP alloy: A study using processing maps

Abstract

Hot compression testing was used to study how the sulfur content affects the hot deformation behavior and processing map of the deoxidized high-phosphorus copper (Cu-DHP) alloy. The results demonstrated that increasing sulfur content from 4 to 356 ppm significantly raises the flow stress. Processing maps indicated that the low-sulfur alloy exhibits a wider domain for dynamic recrystallization (DRX) with high power dissipation index values. However, the domain at low temperature range of 500–650 °C was absent for the high-sulfur alloy, and the flow instability domain at low temperatures and high strain rates became much wider. These observations were supported by the microstructural analysis and it was concluded that sulfur impurity has a serious adverse effect on the hot workability of pure copper. Nevertheless, the high-sulfur alloy showed a finer DRX grain size (D) at the same Zener-Hollomon parameter (Z) due to the retardation effect of sulfur. The simple formulae of D = 2738/Z^0.1136 and D = 11453/Z^0.1980 were proposed for the low-sulfur and high-sulfur alloys, respectively. The hardness (H) values for both alloys were consistent with the single Hall-Petch line of H = 43.38 + 175.47/√D, formulating the effect of grain refinement on the mechanical properties. Finally, the development of the superimposed processing map and grain size map for these alloys was another major contribution of this work.