High-strain-rate solute drag creep in a Cu-22%Sn alloy (Cu17Sn3) with near peritectic composition

Abstract

Hot compressive deformation behavior and processing maps of the cast Cu-22%Sn alloy with near peritectic composition were examined in the temperature range between 843 and 993 K and in the strain rate range between 10−3 and 10 s−1. Solute drag creep associated with a stress exponent of close to 3.5 dominated the plastic flow even at a very high strain rate of 10 s−1, implying that the Cu-22%Sn alloy with a major phase of β (Cu17Sn3, disordered body centered cubic) exhibits high-strain-rate solute drag creep. This is a unique property of the Cu-22%Sn alloy because most of the conventional solid-solution alloys exhibit solute drag creep below 10−3–10−2 s−1. No unstable flow regime appeared in the flow instability maps, and the power dissipation efficiency was high over the entire range of experimental conditions in the power dissipation maps, indicating that the coarse-grained Cu-22%Sn alloy exhibits excellent hot workability at high strain rates. Comparison of the cast Cu-22%Sn alloy with the cast Cu-10%Sn alloy with a single α phase (Cu (α), face centered cubic) indicates that (1) the flow stress of the Cu-22%Sn alloy is considerably lower than that of the Cu-10%Sn alloy (by a factor of 11) and (2) the onset of significant deviation from solute drag creep is estimated to occur at a considerably higher strain rate (by a factor of 105) in the Cu-22%Sn alloy. Possible explanations on these observations were presented.