Effect of small additions of boron on shape memory properties and grain refinement of Cu-Al-Mn SMAs

Cu-12.5 wt.% Al-5 wt.% Mn-(0.05 to 0.2) wt.% B alloys were prepared by ingot metallurgy. The Al and Mn contents of the alloys were maintained constant, while that of B was varied. The ingots were then homogenized followed by step quenching to obtain a fully martensitic structure. The alloys were then characterized by subjecting them to compositional analysis, DSC and microstructural examination. The shape memory effect and superelasticity of the alloys were determined by bend and tensile tests on the alloy specimens. The study reveals that B acts as a good grain refiner, resulting in a reduction of about 80% in grain size. The addition of B also increases the transformation temperatures by - 10°C, while at the same time decreasing the strain recovery by shape memory effect by 4%, and that by superelasticity by ∼2%.