The ternary intermetallic compound Ni2MnGa is an intelligent material, which has a shape memory effect and a ferromagnetic property. Use of shape memory alloy films for an actuator of micro machines is very attractive because of its large recovery force. The data of mechanical and shape memory properties of the films are required to use for the actuator. The purpose of this study is to investigate the effects of fabrication conditions and to clarify the relationships between these properties and fabrication conditions of the Ni2MnGa films. The Ni2MnGa films were deposited with a radio-frequency magnetron sputtering apparatus using a Ni50Mn25Ga25 or Ni52Mn24Ga24 target. After deposition, the films were annealed at 873 ∼ 1173 K. The as-deposited films were crystalline and had columnar grains. After the heat treatment, the grains widened and the grain boundary became indistinct with increasing heat treatment temperature. MnO and Ni3(Mn, Ga) precipitations were observed in the heat-treated films. The mechanical properties of the films were measured by the nanoindentation method. Hardness and elastic modulus of as-deposited films were larger than those of arc-melted bulk alloys. The hardness of the films was affected by the composition, crystal structure, microstructure and precipitation, etc. The elastic modulus of the films was also changed with the heat treatment conditions. The heat-treated films showed a thermal two-way shape memory effect.
|Number of pages
|Journal De Physique. IV : JP
|Published - 2003 Oct
|International Conference on Martensitic Transformations - Espoo, Finland
Duration: 2002 Jun 10 → 2002 Jun 14