Microstructural characterization of gadolinium-rich phases in titanium alloys

Area of Science:

• Materials Science
• Metallurgy
• Physical Chemistry

Background:

• Titanium (Ti) alloys are crucial in various industries.
• Understanding the behavior of alloying elements like gadolinium (Gd) is essential for optimizing Ti alloy properties.
• Gadolinium-rich phases can significantly influence the microstructure and performance of Ti alloys.

Purpose of the Study:

• To comprehensively investigate the microstructural characteristics of gadolinium-rich phases in titanium alloys.
• To elucidate the formation mechanisms and crystallographic nature of these Gd phases.
• To analyze the impact of Gd phase formation on the mechanical properties and processing of Ti-Gd alloys.

Main Methods:

• Plasma arc melting and hot forging for alloy production.
• Electron microscopy (SEM, TEM) for microstructural analysis.
• Electron backscatter diffraction (EBSD) and energy dispersive spectroscopy (EDS) for phase identification and elemental mapping.
• X-ray diffraction (XRD) for crystallographic analysis.

Main Results:

• Formation of round/angular gadolinium oxides and elongated Gd-rich grains.
• Identification of FCC-type γ-Gd phase and Gd₂O₃, influenced by oxygen content.
• Observation of internal twins in Gd grains, potentially inhibiting transformation.
• Defects at phase interfaces due to mechanical property mismatch during hot processing, weakening the Gd phase.

Conclusions:

• The study provides detailed insights into Gd phase formation in Ti alloys.
• Oxygen intake during casting plays a role in the type of Gd phases formed.
• Mechanical property disparities between Gd phases and the Ti matrix lead to processing defects and reduced Gd phase strength.
• Enhanced understanding of Ti-Gd alloy behavior for future material development.