Stabilizing a Fine Twin Structure in Ni–Mn–Ga Samples by Coatings and Ion Implantation
The surfaces of Ni–Mn–Ga samples were coated with hard TiN and soft elastomer and implanted Nb+ ions. All of these treatments stabilized a dense twin structure. After removing the treated surface layers, the original coarse twin structure reappeared. Compression tests of the ion-implanted sample with fine twins exhibited a continuously increasing, smooth stress–strain curve. Without the surface layer, the stress–strain curve was more rugged and flat, the twinning stress decreased, and one twin boundary moved throughout the entire sample.
Ullakko, K.; Chmielus, M.; and Müllner, P. (2015). "Stabilizing a Fine Twin Structure in Ni–Mn–Ga Samples by Coatings and Ion Implantation". Scripta Materialia, 94, pp. 40-43. doi: 10.1016/j.scriptamat.2014.09.013