Actuation properties of a magnetic shape memory element prepared by laser ablation

Abstract:
We used laser ablation (LA) technique to prepare an actuating element from a single crystal of 10M Ni50Mn28Ga22 magnetic shape memory (MSM) alloy, and characterized its structural, magnetic and mechanical properties at ambient temperature. The LA cutting stabilized a fine twin structure with type 1 twins and a twin bilayer width of 25 µm on average. The measurements revealed a magnetic-field-induced strain of 4.5% and a magnetostress of 2.7 MPa in saturating fields. The sample exhibited a twinning stress of 1.02 MPa which was 7% more when compared to an electropolished LAuntreated crystal with fine twins of type 1. We attribute the slight increase of the twinning stress and a moderate increase of the stress-strain loop slope to surface defects generated by LA-cutting. In high-rate pulsed magnetic actuation, the sample demonstrated peak actuation velocities of about 4 m/s in both contraction and elongation modes. Our results demonstrate LA as a promising method for manufacturing actuating elements from MSM alloys, without the need for additional post-processing.