Creep behaviour of eutectic SnBi alloy and its constituent phases using nanoindentation technique

• Creep properties of eutectic SnBi alloy was studied using constant strain rate nanoindentation.
• Its constituent phases, Sn–3%Bi and pure Bi, were also investigated.
• The eutectic alloy shows bi-linear strain rate dependent creep behaviour.
• The stress exponents of Sn–3%Bi and pure Bi are suggestive of power-law-breakdown.

Creep behaviour of eutectic tin–bismuth (SnBi) and its constituent phase materials was studied using constant strain rate (CSR) nanoindentation. Eight strain rates from 5 × 10−4 to 0.1 s−1 were used to assess their strain rate–stress relationship. The stress exponents of 12.25 and 10.09 were found for Sn–3%Bi and pure Bi, respectively, suggesting power-law breakdown (PLB) as the rate controlling mechanism for the two constituent single-phase materials. Strain bursts that appear at the initial stage of loading of the single-phase materials were found to be a prerequisite to cause dislocation creep at the later stage of deformation. Grain boundary sliding (GBS) was found as the complementary mechanism to accommodate grain shape change in Sn–3%Bi and pure Bi as proven by post-indent microstructural examination. Eutectic SnBi showed bi-linear strain rate dependent creep behaviour with the transition at around 2 × 10−3 s−1. Stress exponent of 2.35 was found at low strain rate region suggesting that GBS dominates the creep deformation. At the high strain rate region, stress exponent of 5.20 suggests that dislocation climb in the crystal lattice is the creep mechanism.