Observation of microstructure evolution during inertia friction welding using in-situ synchrotron X-ray diffraction

Area of Science:

• Materials Science
• Metallurgy
• Welding Engineering

Background:

• Inertia friction welding (IFW) is crucial for joining metals, but its development is hindered by limited understanding of deformation and microstructure.
• Accurate numerical models for IFW require detailed knowledge of phase transformations and lattice strains to optimize parameters and reduce experimental costs.

Purpose of the Study:

• To investigate the microstructure evolution during inertia friction welding (IFW) of high-carbon steel.
• To analyze phase transformations and lattice strains at the weld interface.
• To correlate process parameters with microstructural changes for improved modeling.

Main Methods:

• A novel compact rig was employed for in-situ synchrotron X-ray diffraction analysis.
• High-speed X-ray diffraction captured dynamic changes during IFW of BS1407 high-carbon steel.
• Thermal response and phase fractions were measured at the contact interface.

Main Results:

• The transformation of ferrite to austenite at the contact interface was observed in detail.
• Austenite transformation occurred at 500°C, significantly below the equilibrium start temperature of 725°C.
• Large localized strains at the interface were identified as a key factor in the non-equilibrium transformation.

Conclusions:

• Localized strains induced during IFW promote non-equilibrium phase transformations.
• The findings provide critical data for developing robust numerical models for IFW.
• Optimized process parameters can be determined, reducing the need for extensive experimental trials.