Effects of double aging heat treatment on the microstructure, Vickers hardness and elastic modulus of Ti-Nb alloys

Journal Article · Fri Jul 15 04:00:00 EDT 2011 · Materials Characterization

DOI:https://doi.org/10.1016/J.MATCHAR.2011.04.015· OSTI ID:22066374

Lopes, E S.N.; Cremasco, A ^[1]; Afonso, C R.M. ^[2]; Caram, R ^[1]

---

1. University of Campinas, School of Mechanical Engineering (Brazil)
2. Federal University of Sao Carlos, Department of Materials Engineering (Brazil)

Aging heat treatment can be a good way to optimize mechanical properties, changing the microstructure, and hence, the mechanical behavior of Ti alloys. The effects of aging heat treatments on {beta}-type Ti-30Nb alloy were investigated to evaluate the kinetics of {alpha}'' {yields} {alpha} + {beta} transformation. The results obtained from differential scanning calorimetry and high-temperature X-ray diffraction experiments indicated the complete decomposition of orthorhombic {alpha}'' phase at close to 300 deg. C, followed by {alpha} phase precipitation at 470 deg. C. The aging heat treatments also enabled us to observe a transformation sequence {alpha}'' {yields} {beta} + {omega} {yields} {beta} + {omega} + {alpha}, indicating martensite decomposition and {omega} phase precipitation at 260 deg. C after 2 h, followed by {alpha} phase nucleation after heating at 400 deg. C for 1 h. The elastic modulus and Vickers hardness of Ti-30Nb alloy were found to be very sensitive to the microstructural changes caused by heat treatment. - Highlights: {yields} DSC and XRD shed light on the {alpha}'' decomposition and nucleation of {omega} and {alpha} phases. {yields} Aging allows for {alpha}''{yields}{beta} transformation and nucleation of {omega} dispersed in the {beta} matrix. {yields} During aging, {alpha}'' interplanar distances are reduced to enable {beta} phase nucleation. {yields} Mechanical behavior is dependent on the microstructure and the phases in the alloy. {yields} It is not possible to obtain high strength and low elastic modulus by applying aging.

• OSTI ID: 22066374
• Journal Information: Materials Characterization, Journal Name: Materials Characterization Journal Issue: 7 Vol. 62; ISSN 1044-5803; ISSN MACHEX
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
AGING
CALORIMETRY
DECOMPOSITION
HEAT TREATMENTS
MARTENSITE
MATRIX MATERIALS
MICROSTRUCTURE
NIOBIUM ALLOYS
NUCLEATION
ORTHORHOMBIC LATTICES
PHASE TRANSFORMATIONS
PRECIPITATION
TEMPERATURE DEPENDENCE
TITANIUM ALLOYS
TRANSMISSION ELECTRON MICROSCOPY
VICKERS HARDNESS
X-RAY DIFFRACTION