Morphology and Structure of Brass-Invar Weld Interface after Explosive Welding

Area of Science:

• Materials Science
• Metallurgy
• Surface Engineering

Background:

• Thermostatic bimetals, or thermobimetals, are crucial for temperature-sensitive applications.
• Understanding weld interface morphology is key to predicting thermobimetal performance.
• Brass-Invar bimetals offer unique thermal expansion properties.

Purpose of the Study:

• To investigate the morphology and structure of the weld interface in explosively welded brass-Invar bimetals.
• To characterize the phases and crystallographic orientation at the weld interface.
• To elucidate the mechanism of Cu-Zn-Fe-Ni structure formation during explosive welding.

Main Methods:

• Optical microscopy and Scanning Electron Microscopy (SEM) for structural analysis.
• Energy-Dispersive X-ray (EDX) spectrometry and Back-Scattered Electron (BSE) imaging for phase identification.
• Electron Back-Scatter Diffraction (EBSD) with a forward-scatter detector (FSD) for crystallographic orientation mapping.

Main Results:

• The weld interface exhibited a wavy structure characteristic of explosive welding.
• Melted zones at wave crests and troughs contained a disordered Cu-Zn-Fe-Ni solid solution with undissolved Invar particles.
• Brass and Invar grains were strongly elongated, with observed deformation twins, dislocation accumulations, and shear bands.

Conclusions:

• The study successfully characterized the complex microstructure at the brass-Invar weld interface.
• The findings provide insights into the structural evolution and phase formation under explosive welding conditions.
• A proposed mechanism for Cu-Zn-Fe-Ni structure formation contributes to understanding thermobimetal fabrication.