Magnetic Shape Memory Nanocomposites Assembled with High Speed High Pressure Torsion

Area of Science:

• Materials Science and Engineering
• Metallurgy
• Nanotechnology

Background:

• Severe plastic deformation (SPD) processes are versatile, especially at high temperatures.
• High-speed high-pressure torsion (HSHPT) is an SPD method for nanostructure fabrication.
• Previous high-pressure torsion methods had drawbacks, limiting sample size and application.

Purpose of the Study:

• To utilize HSHPT for assembling multiple layers of shape memory nanocomposites.
• To investigate the microstructural evolution and bonding in composite magnetic alloys.
• To overcome limitations of traditional high-pressure torsion techniques.

Main Methods:

• Employed high-speed high-pressure torsion (HSHPT) on cast magnetic alloys (NiFeGa, FePdMn, CoZr).
• Assembled various composites, including ZrCo/FePdMn and ZrCo/NiFeGa.
• Utilized advanced automation and programmable logic controllers for precise parameter control.
• Characterized microstructures using optical microscopy, scanning electron microscopy, energy dispersive spectroscopy, and atomic force microscopy.

Main Results:

• Achieved significant grain refinement and strong layer bonding in ZrCo/FePdMn and ZrCo/NiFeGa composites within seconds.
• HSHPT generated intense friction and heat, leading to rapid temperature pulses dissipated via heat conduction.
• Overcame major drawbacks of high-pressure torsion, producing large SPD discs with well-defined interfaces and ultrafine microstructures.

Conclusions:

• HSHPT is a highly effective and rapid method for fabricating advanced magnetic shape memory nanocomposites.
• The process yields superior microstructural properties, including refined grains and robust layer adhesion.
• This technique offers a promising route for producing bulk nanostructured materials with enhanced properties.