The microstructure and mechanical behavior of beta titanium alloy Ti-15V-3Cr-3Al-3Sn (Ti15-3) under unidirectional and high cycle fatigue (HCF) loading conditions were studied after single aging (SA) and duplex aging (DA). After SA, well-developed grain boundary α and micro precipitate free zones (micro PFZs) were present in the microstructure. Whereas after DA, grain boundary α was poorly developed and micro PFZs were absent. DA resulted in smaller size, higher density and volume fraction of alpha particles. DA led to higher work hardening rate, better strength-ductility combination and higher HCF life. Improved mechanical behavior after DA is explained based on microstructural observations. © 2014 Elsevier Ltd. All rights reserved.

Geetha M

Department of Control and Automation

School of Electrical Engineering

Vellore Campus

Nageswara Rao M

Department of Manufacturing Engineering

School of Mechanical Engineering

Santhosh R

Saxena V.K

Vellore Institute of Technology (VIT) is a private university located in&nbsp;Tamil Nadu, India. Founded in 1984, as Vellore Engineering College, the institution offers 20 undergraduate, 34 postgraduate, four integrated and four research programs. It has campuses in Vellore, Amravati, Bhopal and Chennai.

VIT is one of the top ranked private universities in India according to NIRF, THE and QS Rankings.&nbsp;Govt. of India has recognized&nbsp;VIT, Vellore as an&nbsp;Institution of Eminence. This has allowed VIT to take independent quality initiatives and move up in world ranking.

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VIT University

International Journal of Fatigue

The paper presents a study of the surface and subsurface characteristics induced by laser peening without coating (LPwC) and dual shot peening (DSP) on the duplex aged Ti-15 V-3Al-3Cr-3Sn alloy. In 3D-optical topography analysis, DSP resulted in a six-fold enhancement in the surface roughness (Sa). Whereas, LPwC resulted in unaltered surface roughness (Sa) compared to the polished/unpeened sample. In cross-sectional microstructure studies, deformed grains and heat affected zones were observed in the near surface region of shot peened, and laser peened samples respectively. Moreover, compared to bulk hardness, shot peening and laser peening has resulted in maximum increment of ~28% and ~12% in microhardness of the near peened surface region respectively. © 2020, Springer Nature Singapore Pte Ltd.

Lecture Notes in Mechanical Engineering Advanced Surface Enhancement

A Comparison of Surface and Sub-surface Features Induced by Shot Peening vs. Laser Peening on a Duplex Aged Beta Ti Alloy

In the present study, Ti-15V-3Al-3Cr-3Sn (Ti-15-3), a beta titanium aerospace alloy in solution treated condition (850 °C/1 h) was subjected to Laser Peening without Coating (LPwC) with a wavelength of 532 nm and power density of 8.96 GW cm−2. Surface roughness was analysed using 3D optical topography. Curiously, in the near peened surface, peening induced precipitation (i.e. 19% of α precipitation) and increased fraction of low angle boundaries (∼123%) was revealed through the Electron Back Scattered Diffraction (EBSD) analysis. Through depth nanohardness measurement was carried out along the cross-section of the peened sample right from the near peened surface. Peak hardness of 4.6 GPa is observed at a depth of 100 µm from the peened surface while the base/bulk hardness of the material is 4 GPa. In addition, X-Ray Diffraction (XRD) based analysis confirmed the presence of compressive residual stress in the near surface region of the peened sample. To understand the effect of the peening induced microstructural changes and residual stresses in fatigue behaviour, staircase method of fatigue analysis was adopted and observed that the more number of run out samples belonged to laser peened condition when compared to the unpeened condition. Despite this favourable indication, fatigue limit remains more or less unaltered even after peening. Fractography studies revealed the least influence of the surface roughness induced by laser peening over the crack initiation. Irrespective of the condition (i.e. unpeened and laser peened), crack initiation was predominantly influenced by the stress concentration co-existing at the sharp corners. © 2018 Elsevier Ltd

Optics & Laser Technology

Influence of laser peening without coating on microstructure and fatigue limit of Ti-15V-3Al-3Cr-3Sn

Environmentally induced degradation is a serious issue governing the use of titanium alloy fasteners for marine applications. The workhorse alloy Ti6Al4V which has been the most used titanium alloy till date as fastener material has its limitations and search has been on for improved titanium-based materials. This paper deals with researches aimed at evaluating the metastable beta titanium alloy Ti15V3Cr3Al3Sn (Ti15-3) in solution annealed condition as a fastener material for medium strength applications. A variety of tests was carried out to rate the resistance of the alloy in this condition to seawater environments slow strain rate testing (SSRT), crevice corrosion testing, potentiodynamic polarization studies, and immersion testing. Limited SSRT was also done on Ti6Al4V for the sake of comparison. Analysis of test results shows that solution annealed Ti15-3 offers itself as a good candidate material for medium strength fastener applications in marine environments. © 2018

Journal of Alloys and Compounds

Degradation behavior of metastable β Ti-15-3 alloy for fastener applications

Fulltext

Titanium Alloys - Novel Aspects of Their Processing [Working Title]

Processing of Beta Titanium Alloys for Aerospace and Biomedical Applications

Beta titanium (β-Ti) alloys have been a subject area of intense interest since 1980s. By virtue of their unique properties, β-Ti alloys very well compliment the alpha and alpha + beta alloys. Heat treatment of β-Ti alloys is the crux to their technology and application. Over the last two decades, a number of researches have been carried out on issues related to heat treatment of these alloys—sub-transus solution treatment, duplex aging and heating rate to aging temperature. Improved understanding resulting from these studies has enabled designing optimum heat treatments to achieve refined microstructures free from deleterious features with improved mechanical properties under static and dynamic loading conditions. The purpose of this overview is to take stock of progress made in recent years in understanding the heat treatment of β-Ti alloys for a better commercial exploitation. © 2016, The Indian Institute of Metals - IIM.

Transactions of the Indian Institute of Metals

Recent Developments in Heat Treatment of Beta Titanium Alloys for Aerospace Applications

The kinetics of the β → α + β phase transformation in Ti-15V-3Cr-3Al-3Sn (Ti15-3) alloy was studied at 500 °C. A method is proposed and used to estimate the volume fraction of α phase as a function of aging time based on X-ray diffraction (XRD). The method uses the results of calculations of phase equilibria at 500 °C performed using Thermo-Calc. The present work also reports results of calculations of phase equilibria over the temperature range 200-600 °C. In order to validate XRD based approach, select measurements of the quantity of α phase precipitation were done by the use of Field Emission Scanning Electron Microscopy. Results obtained were in reasonable agreement with those obtained using XRD. The kinetics of the β → α + β phase transformation was modelled in the theoretical framework of the Johnson-Mehl-Avrami (JMA) theory and a mechanism based on slow diffusion controlled growth of very fine α plates is proposed. Using the derived JMA kinetic parameters, fraction of transformed α was calculated as a function of aging time; the calculated and experimentally measured values were found to be in good agreement. © 2014 Elsevier B.V. All rights reserved.

Experimental study and computer modelling of the β → α + β phase transformation in Ti15-3 alloy under isothermal conditions

This paper presents the age hardening behavior of metastable beta titanium alloy Ti-15 V-3Cr-3Al-3Sn subjected to various single and duplex aging treatments. Single aging was carried out in the range 200-550 °C for times up to 150 h (h). For duplex aging first step was performed in two different ways: (i) 250 °C for 24 h (ii) 300 °C for 10 h; second step was carried in the range 350-500 °C, for times up to 150 h. The decomposition of alpha (α) phase during aging was monitored by hardness measurements, tensile testing, different microscopic techniques and X-ray diffraction. Duplex aging treatments resulted in higher hardness and strength compared to single aging. There was a good balance of tensile strength and ductility after two duplex aging treatments 300 °C/10 h + 500 °C/10 h and 250 °C/24 h + 500 °C/8 h. Precipitate free zones (PFZs) were observed when aged at ≤450 °C in the microstructure; aging at ≥500 °C gave freedom from such zones. Duplex aging resulted in a finer size and higher density of α precipitates compared to single aging. Duplex aging 250 °C/24 h + 500 °C/8 h led to a four to five fold improvement in high cycle fatigue (HCF) life compared to single aging at 500 °C/10 h. The observed improvement in HCF life could thus be related to smaller size and larger density of α precipitates resulting from duplex aging. Optical microscopy and X-ray diffraction studies clearly revealed that preaging for 10 h at 300 °C accelerated the α-phase precipitation reaction during aging. © 2014 Elsevier B.V. All rights reserved.

Studies on single and duplex aging of metastable beta titanium alloy Ti–15V–3Cr–3Al–3Sn

Materials & Design

Effect of solution treatment and aging on microstructure and tensile properties of high strength β titanium alloy, Ti–5Al–5V–5Mo–3Cr

Effect of heat treatment on microstructure and mechanical properties of a new β high strength titanium alloy

Effect of aging heat treatment on microstructure and tensile properties of a new β high strength titanium alloy

Effect of duplex aging on microstructure and mechanical behavior of beta titanium alloy Ti–15V–3Cr–3Al–3Sn under unidirectional and cyclic loading conditions

Journal	Data powered by TypesetInternational Journal of Fatigue
Publisher	Data powered by TypesetElsevier BV
ISSN	0142-1123
Open Access	0