Design and implementation of a multiaxial loading capability during heating on an engineering neutron diffractometer

Area of Science:

• Materials Science
• Neutron Scattering
• Mechanical Engineering

Background:

• In situ neutron diffraction is crucial for understanding material behavior under stress.
• Existing methods often lack the capability for complex multiaxial loading and high temperatures.
• Advanced gripping systems are needed to push the boundaries of materials characterization.

Purpose of the Study:

• To design, implement, and test a novel gripping capability for in situ neutron diffraction.
• To enable simultaneous multiaxial loading (tension, compression, torsion) and heating during experiments.
• To investigate the deformation mechanisms of Nickel-Titanium (NiTi) shape memory alloys.

Main Methods:

• Development of Inconel 718 grips with integrated cooling passages for temperatures up to 1000 K.
• Integration with an MTS load frame (100 kN axial, 400 N·m torsional capacity).
• Utilization of specialized specimen mounting couplers for precise sample handling.
• Acquisition of neutron spectra during various loading and thermal conditions.

Main Results:

• Successful implementation and testing of the multiaxial loading and heating gripping system.
• Demonstrated capability for in situ neutron diffraction measurements under complex load paths.
• Preliminary results show quantification of texture, internal strain, and phase fraction evolution in NiTi alloys.
• Characterization of NiTi deformation under isothermal, isobaric, and cyclic loading modes.

Conclusions:

• The developed gripping capability significantly enhances in situ neutron diffraction analysis for materials under complex thermomechanical conditions.
• This system provides unprecedented insights into the deformation physics of advanced materials like NiTi shape memory alloys.
• The methodology facilitates a deeper understanding of structure-property relationships during material transformation and failure.