Alfa phase nucleation in metastable beta Ti-Nb-Fe-Sn alloy: intergranular and intragranular precipitation mechanisms

• Grant number: 21/06156-9
• Support Opportunities: Scholarships in Brazil - Doctorate
• Effective date (Start): July 01, 2022
• Effective date (End): December 31, 2025
• Field of knowledge: Engineering - Materials and Metallurgical Engineering - Physical Metallurgy
• Principal Investigator: Rubens Caram Junior
• Grantee: Leticia Falcão Starck
• Host Institution: Faculdade de Engenharia Mecânica (FEM). Universidade Estadual de Campinas (UNICAMP). Campinas , SP, Brazil
• Associated research grant: 18/18293-8 - Titanium alloys: phase transformations and additive manufacturing applied to obtaining functionally graded materials, AP.TEM

Abstract

Aging heat treatments applied to metastable beta Ti alloys produce fine alpha phase precipitation into the beta phase matrix. When this precipitation is based on heterogeneous nucleation assisted by omega phase, such a precipitation is predominantly intragranular. However, aging can also produce intergranular precipitation assisted by grain boundaries. Intergranular precipitation is undesirable and detrimental to mechanical properties. In this context, this research aims to investigate aging heat treatment conditions applied to the Ti-19Nb-2,5Fe-6Sn alloy (recently developed in this research group) and explore the competition between intragranular and intergranular precipitations. The secondary objectives of this work are (a) to investigate the omega isothermal phase precipitation through thermal analysis, X-ray diffraction and hardness tests; (b) to investigate isothermal omega phase dissolution through thermal analysis, X-ray diffraction and hardness tests; (c) to investigate alpha phase precipitation (intragranular and intergranular) through thermal analysis, X-ray diffraction, hardness and microstructural analysis, and (d) to investigate the effect of this intergranular/intragranular precipitation on mechanical behavior of Ti-19Nb-2,5Fe-6Sn alloys (wt.%), particularly in fracture morphology. At the end of this work, we intend to advance the knowledge on the intergranular and intragranular alpha phase precipitations. (AU)