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Microstructural and mechanical properties of welded Ti-15-3 beta titanium alloy using GTAW with boron-modified fillers / Ahmad Lutfi Anis

Mechanical properties of titanium alloys are dictated by their microstructure, particularly the size, shape and distribution of hexagonally close-packed (hcp) α and body-centred cubic (bcc) β phases. For metastable β titanium alloys the morphology and distribution of α precipitates have largely cont...

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Main Author: Anis, Ahmad Lutfi
Format: Thesis
Language:English
Published: 2017
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Physical and theoretical chemistry
Online Access:http://ir.uitm.edu.my/id/eprint/21619/1/TP_AHMAD%20LUTFI%20ANIS%20AP%2017_5.pdf
http://ir.uitm.edu.my/id/eprint/21619/
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spelling my.uitm.ir.216192018-09-26T03:32:30Z http://ir.uitm.edu.my/id/eprint/21619/ Microstructural and mechanical properties of welded Ti-15-3 beta titanium alloy using GTAW with boron-modified fillers / Ahmad Lutfi Anis Anis, Ahmad Lutfi Physical and theoretical chemistry Mechanical properties of titanium alloys are dictated by their microstructure, particularly the size, shape and distribution of hexagonally close-packed (hcp) α and body-centred cubic (bcc) β phases. For metastable β titanium alloys the morphology and distribution of α precipitates have largely contributed to its mechanical properties. Welded zones in gas tungsten arc welding (GTAW) of metastable β titanium alloys exhibit retained β structure with inferior mechanical properties due to coarse columnar prior β grains and lack of α precipitates in the matrix in as-welded condition. In this work refinement of prior β grains and α. was achieved in GTAW welds of metastable β titanium alloy, Ti-15V-3Cr-3Al-3Sn (Ti-15-3) by current pulsing and modification of welding fillers. Autogenous pulsed current GTAW were performed at 0, 2, 4 and 6 Hz pulsing frequencies to determine optimum frequency for pulsed current welding of thin plates Ti-15-3 alloy. Welding of Ti-15-3 alloy using commercially pure α titanium (CPTi) alloy filler resulted in the precipitation of α phase from β phase during cooling to ambient temperature due to dilution of melted base metal with the filler metal. The GTAW welds with CP-Ti filler exhibit high hardness, higher tensile strength but lower % strain as compared to the autogenous weld owing to precipitation of a phase precipitation at β grain boundaries. Addition of 0.5 wt.% and 1.0 wt.% boron to CP-Ti fillers resulted in significantly refined fusion zone β grains in welds with CP-Ti-0.5B and CP-Ti-1 .0B fillers due to growth restriction mechanism associated with partitioning of boron during solidification. X-ray diffraction (XRD) analysis of autogenous welds showed only bcc β-Ti phase while indexed peaks for the weld samples with CP-Ti filler showed the presence of very small hcp α-Ti phase along with bcc β-Ti phase. Welds with CP-Ti-0.5B and CP-Ti-1.0B fillers showed additional orthorhombic TiB peaks. Mechanical tests show that hardness of the fusion zone and tensile strength in welds with boron-added CP-Ti fillers are higher than that in autogenous welds and welds with CP-Ti filler. Post-weld heat treatment (PWHT) of the welded samples increased α precipitation in all samples while FESEM and TEM analysis of the fusion zones showed α with higher aspect ratios in aged welds with boron-added CP-Ti fillers than autogenous weld and weld with CP-Ti filler, attributed to the additional nucleation sites provided by increase in boundary area of refined prior β grains with the addition of boron. PWHT weldments displayed higher hardness values, compared to similar regions in as-welded samples, and higher tensile strength after aging. 2017 Thesis NonPeerReviewed text en http://ir.uitm.edu.my/id/eprint/21619/1/TP_AHMAD%20LUTFI%20ANIS%20AP%2017_5.pdf Anis, Ahmad Lutfi (2017) Microstructural and mechanical properties of welded Ti-15-3 beta titanium alloy using GTAW with boron-modified fillers / Ahmad Lutfi Anis. PhD thesis, Universiti Teknologi MARA.
institution Universiti Teknologi Mara
building Tun Abdul Razak Library
collection Institutional Repository
continent Asia
country Malaysia
content_provider Universiti Teknologi Mara
content_source UiTM Institutional Repository
url_provider http://ir.uitm.edu.my/
language English
topic Physical and theoretical chemistry
spellingShingle Physical and theoretical chemistry
Anis, Ahmad Lutfi
Microstructural and mechanical properties of welded Ti-15-3 beta titanium alloy using GTAW with boron-modified fillers / Ahmad Lutfi Anis
description Mechanical properties of titanium alloys are dictated by their microstructure, particularly the size, shape and distribution of hexagonally close-packed (hcp) α and body-centred cubic (bcc) β phases. For metastable β titanium alloys the morphology and distribution of α precipitates have largely contributed to its mechanical properties. Welded zones in gas tungsten arc welding (GTAW) of metastable β titanium alloys exhibit retained β structure with inferior mechanical properties due to coarse columnar prior β grains and lack of α precipitates in the matrix in as-welded condition. In this work refinement of prior β grains and α. was achieved in GTAW welds of metastable β titanium alloy, Ti-15V-3Cr-3Al-3Sn (Ti-15-3) by current pulsing and modification of welding fillers. Autogenous pulsed current GTAW were performed at 0, 2, 4 and 6 Hz pulsing frequencies to determine optimum frequency for pulsed current welding of thin plates Ti-15-3 alloy. Welding of Ti-15-3 alloy using commercially pure α titanium (CPTi) alloy filler resulted in the precipitation of α phase from β phase during cooling to ambient temperature due to dilution of melted base metal with the filler metal. The GTAW welds with CP-Ti filler exhibit high hardness, higher tensile strength but lower % strain as compared to the autogenous weld owing to precipitation of a phase precipitation at β grain boundaries. Addition of 0.5 wt.% and 1.0 wt.% boron to CP-Ti fillers resulted in significantly refined fusion zone β grains in welds with CP-Ti-0.5B and CP-Ti-1 .0B fillers due to growth restriction mechanism associated with partitioning of boron during solidification. X-ray diffraction (XRD) analysis of autogenous welds showed only bcc β-Ti phase while indexed peaks for the weld samples with CP-Ti filler showed the presence of very small hcp α-Ti phase along with bcc β-Ti phase. Welds with CP-Ti-0.5B and CP-Ti-1.0B fillers showed additional orthorhombic TiB peaks. Mechanical tests show that hardness of the fusion zone and tensile strength in welds with boron-added CP-Ti fillers are higher than that in autogenous welds and welds with CP-Ti filler. Post-weld heat treatment (PWHT) of the welded samples increased α precipitation in all samples while FESEM and TEM analysis of the fusion zones showed α with higher aspect ratios in aged welds with boron-added CP-Ti fillers than autogenous weld and weld with CP-Ti filler, attributed to the additional nucleation sites provided by increase in boundary area of refined prior β grains with the addition of boron. PWHT weldments displayed higher hardness values, compared to similar regions in as-welded samples, and higher tensile strength after aging.
format Thesis
author Anis, Ahmad Lutfi
author_facet Anis, Ahmad Lutfi
author_sort Anis, Ahmad Lutfi
title Microstructural and mechanical properties of welded Ti-15-3 beta titanium alloy using GTAW with boron-modified fillers / Ahmad Lutfi Anis
title_short Microstructural and mechanical properties of welded Ti-15-3 beta titanium alloy using GTAW with boron-modified fillers / Ahmad Lutfi Anis
title_full Microstructural and mechanical properties of welded Ti-15-3 beta titanium alloy using GTAW with boron-modified fillers / Ahmad Lutfi Anis
title_fullStr Microstructural and mechanical properties of welded Ti-15-3 beta titanium alloy using GTAW with boron-modified fillers / Ahmad Lutfi Anis
title_full_unstemmed Microstructural and mechanical properties of welded Ti-15-3 beta titanium alloy using GTAW with boron-modified fillers / Ahmad Lutfi Anis
title_sort microstructural and mechanical properties of welded ti-15-3 beta titanium alloy using gtaw with boron-modified fillers / ahmad lutfi anis
publishDate 2017
url http://ir.uitm.edu.my/id/eprint/21619/1/TP_AHMAD%20LUTFI%20ANIS%20AP%2017_5.pdf
http://ir.uitm.edu.my/id/eprint/21619/
_version_ 1685649493974843392
score 13.211869

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