Thermal Stability of Hardness and Modulus in Martensitic Ti–6Al–4V-Based Alloys: Role of V, Fe, and Ge Solute Contents

This study investigates the influence of V, Fe, and Ge additions on the evolution of the martensite phase in Ti–6Al–4V alloy, with a specific focus on the microstructure and mechanical properties such as hardness and elastic modulus. The addition of these elements affects the β transus temperature,...

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Published in:Metallurgical and materials transactions. A, Physical metallurgy and materials science Physical metallurgy and materials science, 2024-04, Vol.55 (4), p.1258-1270
Main Authors: Chaithanya Kumar, K. N., Varukuti, Shashi Mohan Rao, Suresh, K. S.
Format: Article
Language:English
Subjects:
Alloying
Alloys
Boundaries
Characterization and Evaluation of Materials
Chemistry and Materials Science
Fractions
Germanium
Hardness
High temperature
Martensite
Materials Science
Mechanical properties
Metallic Materials
Modulus of elasticity
Nanotechnology
Original Research Article
Solid solutions
Solution strengthening
Stacking faults
Structural Materials
Surfaces and Interfaces
Temperature
Thermal stability
Thin Films
Titanium base alloys
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Summary:This study investigates the influence of V, Fe, and Ge additions on the evolution of the martensite phase in Ti–6Al–4V alloy, with a specific focus on the microstructure and mechanical properties such as hardness and elastic modulus. The addition of these elements affects the β transus temperature, showing 25 pct decrease in the thickness of the martensite lath with an increased solute content from Ti–6Al–4V to Ti–6Al–5V–1Fe–2Ge. Furthermore, the impact of alloying additions on the character and fraction of intervariant boundaries present between martensite laths are reported. Remarkably, the dominant intervariant boundaries remain consistent across various alloys, revealing three significant angle-axis pairs associated with the Burgers orientation relationship: 60 deg/ [ 1 1 2 ¯ 0 ] α ′ , 60.83 deg/ [ 1.377 ¯ 1 ¯ 2.377 0.359 ] α ′ , and 63.26 deg/ [ 10 ¯ 5 5 , 3 ¯ ] α ′ . These pairs exhibit a similar distribution of intervariant boundary characteristics. In addition, the introduction of Fe and Ge into the Ti–6Al–4V alloy enhances the probability of the stacking fault. The hardness of the martensitic Ti–6Al–5V–1Fe–2Ge alloy demonstrates a remarkable resilience to temperature variations, showing less than 6 pct decrease in hardness with increasing the temperature from ambient condition to 400 ∘ C , while many other alloys exhibit nearly a 25 pct decrease. The observed enhancement in hardness is attributed to solid solution strengthening, both at room and high temperatures.
ISSN:1073-5623
1543-1940
DOI:10.1007/s11661-024-07332-9