Keywords

Abstract

Copper-based alloys; 

Surface morphology; 

Grain characteristics; 

Rare earth metal;

 Mechanical properties;

 Corrosion behavior

The study investigated the grain size criteria, mechanical characteristics, and corrosion behavior of Cu-14Al-4.5Ni-0.7Mn shape memory alloy (SMA) with the micro-addition of 0.06 wt% Lanthanum (La). Using standard melting and casting procedures, the alloy compositions were melted at 1300 ℃ in an arc furnace with an argon atmosphere. The cast compositions without thermal treatment were machined and tested for physical properties including density and percentage porosity, corrosion behavior, and mechanical properties like hardness, ultimate tensile strength, yield strength, fracture strain, percentage elongation, specific strength, and fracture toughness. The average grain size, profile plot, and grain size distribution were all determined using ImageJ software. The microstructural observations revealed the presence of α-phase, β-phase, and intermetallic phases, including the coarse α+γ2 phase, which contributed to the improved characteristics. The inclusion of lanthanum resulted in a drop in the average grain size of the parent alloy from 9.25 μm to 6.08 μm, indicating a clear correlation between property improvement and microstructure refinement. The composition's tensile strength and yield strength increased with the La micro-addition by 22.14% and 20.31% respectively while the hardness value increased by 17.3%. The fracture strain of the modified composition increased by 20% compared to the unmodified composition while the percentage elongation increased by 7.7% and a 22.5% increase in fracture toughness was achieved. The modified CuAlNiMn SMA also showed a significant improvement in corrosion resistance to NaCl solutions which was so evident at 144 hours of the study for 0.5 M of NaCl solution and at 96 hours for 1.0 M of NaCl solution. The results showed that CuAlNiMn SMA with micro-addition of La had better physical, corrosion, and mechanical characteristics than unmodified CuAlNiMn alloys.

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