The effect of crystallographic orientation on the mechanical behavior of Cu₆Sn₅ by micropillar compression testing

The anisotropy of the micromechanical behavior of single-crystal Cu ₆Sn₅ was studied by nanoindentation and microcompression testing of pillars. Electron backscattered diffraction was employed to determine the crystallographic orientation and texture of Cu₆Sn₅ nodules. Characterization results from orientation imaging mapping show that the growth direction of the nodules is somewhat aligned to the c-axis of the unit cell of Cu₆Sn₅, although a fair amount of deviation exists in several grains. Normal to the growth axis the orientation is random, indicating a fiber texture. The mechanical properties indicate a 20% increase in strength and 7% increase in Young's modulus close to the c-axis relative to normal to the c-axis. Careful analysis of the results based on angle to the c-axis shows a linear decrease in strength with increasing deviation from the c-axis. Our results should help understanding and fracture modeling of Cu ₆Sn₅ under thermal and mechanical loading conditions.