Mechanical properties of CoSn_2 and α-CoSn_3 intermetallic compounds: first-principles calculations and nano-indentation measurements

摘要

Structural stability and mechanical properties of CoSn2 and -CoSn3 intermetallic compounds (IMCs) were investigated by first-principles calculations and nano-indentation measurements. The systematical works of the phase stability, elastic constants, and electronic structures were carried out to understand the mechanical properties of CoSn2 and -CoSn3 IMCs. The results showed that the calculated Young's modulus of CoSn2 and -CoSn3 was 149.36 and 138.51 GPa, respectively. In both cases, the major contribution to total density of states (DOS) was Co-d, Sn-s, and Sn-p states and ionic bonds formed between nearest-neighbor Co and Sn atoms. The analyses about electronic structures indicated that the bonding strength of Co-Sn in -CoSn3 was stronger than that in CoSn2, which made it easy to understand the differences of phase stability and mechanical properties between CoSn2 and -CoSn3 IMCs. By means of nano-indentation, the Young's modulus and hardness were measured to be 151.90 +/- 7.21 GPa and 6.43 +/- 0.46 GPa for CoSn2 IMC, while 144.3 +/- 8.36 GPa and 6.28 +/- 0.63 GPa for -CoSn3, respectively. By combining experimental methods and first-principles, it was clearly illustrated that the mechanical properties of CoSn2 were better than that of alpha-CoSn3.