Nanomechanical analysis of the mechanical behaviour of selected up-quenched and step-quenched Cu–Zn–Sn shape memory alloys

The impact of quenching treatment on the mechanical characteristics of Cu–Zn–Sn-based SMAs is investigated using nanoindentation approach conducted at 100–200 mN loads. Two compositions labeled A (Cu 71·19 Zn 15·6 Sn 12·1 Fe 1.05 ) and B (Cu 63·73 Zn 26·1 Sn 9·3 Fe 0.82 ) were subjected to step/up-quenching procedures. The microstructure was composed of Cu 4 and γ -Cu 5 Zn 8 parent phases with sparse distribution Fe 4 and Cu 3 Sn precipitates in the matrix for the up/step-quenched A samples. The step-quenched B samples comprised Cu 3 Sn and Fe 4 Zn 9 precipitates in Cu4 and γ -Cu 5 Zn 8 parent phases, whereas the up-quenched B samples is composed of Cu 3 Sn and Fe 7 Zn 3 second phases. The nanomechanical properties of composition B samples were generally superior to those of composition A samples. For B alloys, the superelasticity increased from 91.91 %, 86.97 %, and 85.01 % at 100 mN load to 93.41 %, 91.80 %, and 88.75 % at 200 mN load for the step-quenched, up-quenched, and direct-quenched samples, respectively. The reduced elastic modulus at 100 mN lie in the range of 122.23–131.84 GPa for the step-quenched samples; 119.86–128.81 GPa for the up-quenched samples; and 116.79–125.16 GPa for the direct-quenched samples. Step-quenching thermal procedure efficiently enhanced the nanomechanical characteristics of the alloys.