Tensile Behavior and Superplastic Deformation of Sn–Bi–Cu Alloy

Abstract

The purpose of this study is to clarify the tensile behavior and deformation mechanism of the Sn40Bi0.1Cu alloy (mass%). Tensile tests of Sn40Bi0.1Cu were performed at temperatures of 298, 333, and 353 K and strain rates from 5.25 © 10 ¹5 to 5.25 © 10 ¹2 s ¹1 . The tensile strength decreased and the elongation increased with increasing temperature and decreasing strain rate. Sn40Bi0.1Cu shows superplastic behavior at temperatures of >333 K and low strain rates of <5.25 © 10 ¹4 s ¹1 . Microstructural observation after superplastic deformation of Sn40Bi0.1Cu showed that the primary crystal Sn grains could not deform along the axial direction of applied tension in the superplastic regime. The eutectic phase contributed to superplastic deformation. The strain rate sensitivity m for Sn40Bi0.1Cu was <0.3.

Effect of Sb and Zn Addition on the Microstructures and Tensile Properties of Sn–Bi-Based Alloys

“…The m value calculated from the slopes of the lines shown in Figure 13 is lower than the critical value of 0.3, indicating that the alloys are characterized by fine-grained superplasticity. This result is similar to previous findings reported for Sn-40Bi-0.1Cu and Sn-40Bi-0.01Ni [24,25]. Because the microstructures and average grain sizes of the Sn-40Bi-Sb alloys are similar to those of Sn-40Bi-0.1Cu, the m value of the Sn-40Bi-Sb alloys also increases with the increasing Sb concentration.…”

“…In general, the stress-strain curves of the Sn-40Bi-Sb alloys are similar to those of Sn-40Bi-0.1Cu and Sn-40Bi-0.01Ni [24,25]. Figure 7 shows the stress-strain curves of the Sn-40Bi-Sb alloys at 353 K under a strain rate of 5.25 × 10 −4 s −1 .…”

“…Thus, the reduction in the area and elongation of the Sn-40Bi-Sb alloys increases with an increasing concentration of Sb. In general, the stress-strain curves of the Sn-40Bi-Sb alloys are similar to those of Sn-40Bi-0.1Cu and Sn-40Bi-0.01Ni [24,25]. Figure 7 shows the stress-strain curves of the Sn-40Bi-Sb alloys at 353 K under a strain rate of 5.25 × 10 −4 s −1 .…”

“…Whether th correlation between the needle-like Zn particles and the number of voids is unknow the tendency of the elongation to decrease with the increasing Zn concentration is c ered to be related to the number of voids in the specimens. At high temperatures a strain rates, which are conducive to superplastic behavior, specimens do not sh markable elongation of the primary Sn phase in the tensile direction; cracks and vo observed to be segregated at the grain boundaries around the intermetallic comp [25]. These results indicate that void accumulation begins from the intermetalli pounds or metal particles, and the final structure of the alloy may be different fr initial dendritic structure.…”

“…However, the superplasticity mechanism of Sn-based alloys has not Materials 2022, 15, 884 2 of 11 been clearly established. In previous studies, the tensile behavior of Sn-Bi-Cu and Sn-Bi-Ni alloys has been investigated, and the corresponding results indicated that these alloys show superplasticity at high temperatures and low strain rates [24,25]. Cu and Ni occupy a small solid-solution region in the Sn phase diagram and easily form an intermetallic compound with the metal.…”