Influence of minor additions of boron and zirconium on shape memory properties and grain refinement of a Cu-Al-Mn shape memory alloy

Cu- base alloys with 12.5 wt. % Al and 5 wt. % Mn with different amounts (0.05- 2.00 wt.%) of boron or zirconium were prepared by ingot metallurgy route. The alloy ingots were homogenized followed by step quenching so as to obtain a structure that is completely martensitic. They were subsequently characterized by optical emission spectrophotometry, differential scanning calorimetry and optical microscopy. The shape memory and superelastic properties of the alloys were studied by bend and tensile test. The present study brings to light that boron acts as a good grain refiner, resulting in a reduction of about 80% in grain size. While it also increases the transformation temperatures by similar to 10 degrees C, it decreases the strain recovery by shape memory effect by 4%, and that by superelasticity by similar to 2%. A comparison of the results of the alloy with B addition with that with Zr addition reveals that B is a better grain refiner for Cu-Al-Mn SMAs.