Magnetic Field-Induced Phase Transformation in Magnetic Shape Memory Alloys with High Actuation Stress and Work Output

摘要

The main goal of the project centers on the idea of identifying, fabricating, characterizing and modeling new magnetic shape memory alloys (MSMAs) and compositions to utilize field-induced phase transformation (FIPT) with the objective of obtaining large actuation stresses, large reversible actuation strains, work outputs, and operating temperature ranges. The novelty of the project arises from the utilization of a new magneto-mechanical mechanism in achieving high work output actuator materials (with the possibility of superior sensing and passive power generation capabilities) from the new MSMAs. The major accomplishments of the project include: 1) the design of a NiMnCoIn composition that resulted in reversible FIPT under magnetic field magnitudes much less than what has been reported in iron based alloys; 2) growth of large single crystals from this composition, 3) the demonstration of magnetostress levels larger than 20 MPa/Tesla in the designed composition utilizing FIPT whereas all previously reported magnetostress levels have been always less than 10MPa/Tesla regardless of the alloy system, composition, and magneto-microstructural mechanism; 4) the investigation of complex magneto- mechanical loading paths; and 5) the analysis of nonlinear magnetostatic boundary value problems for MSMAs using finite element method and taking into account FIPT.