Growth and Characterization of Pre-Oriented Near Net-Shape Grown Ni2MnGa Single Crystals

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Student Presentation

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Peter Müllner


Ni2MnGa is a magnetic shape memory alloy (MSMA) which changes its shape when exposed to a variable magnetic field. The shape change is achieved through the magnetic-field-induced motion of twin boundaries. Single crystals of Ni2MnGa demonstrate the highest magnetic-field-induced strains. In this study, the Bridgman–Stockbarger technique was used to produce near-net-shaped grown single crystals of Ni2MnGa. Single crystals were comprised of high purity elements that were melted and mixed in an induction furnace and then crushed into a fine powder. The powder was loaded into an alumina crucible with a rectangular cross section with a pre-oriented Ni2MnGa seed that was crystallographically oriented with {100} parallel to the crucible faces and parallel to the growth direction. The powder was then driven into a tube furnace, melted down to the seed and then slowly drawn out of the furnace to solidify as a rectangular single crystal in the orientation dictated by the seed. This study highlights the characterization and shaping techniques used to create the seed crystals. Near-net-shaped growth of oriented single crystals reduces or even removes expensive post-growth processing.

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