Welding of titanium alloys

Tim Pasang,Yuan Tao,Mana Azizi,Masami Mizutani,Osamu Kamiya,Wojciech Misiolek,Gow-Yi Tzou

doi:10.1051/matecconf/201712300001

Abstract

This article briefly summarises previous reports as well as some recent results on welding of various titanium alloys. Titanium is available in a wide range, hence, their properties and characteristics (including welding characteristics) may also varied significantly. The alloys studied represented three major areas; they are (1): unalloyed or commercially pure titanium (CP Ti), (2): near α and α+β alloys, and (3): β alloys. From our preliminary results, it can be reported that the structure of fusion zone (FZ) and heat affected zone (HAZ) of alloys from area (1) may change but their hardness remained, arguably, the same as the as-received material. Alloys from area (2) showed an increase in hardness in the FZ and HAZ areas due to the formation of α-prime or martensite, while alloys from area (3) experienced a reduction in hardness associated with dissolution of α phase leaving only retained β in the FZ. Further investigations are required to confirm these findings. Such information are very useful so that appropriate post welding heat treatment (PWHT) can be applied to improve their properties and performance.

Highlights

Titanium and its alloys are used in many different areas such as aerospace, automotive, sporting equipment, chemical, marine and medical due to their excellent high strength-to-weight ratio, good creep resistance, excellent corrosion resistance, good biocompatibility, etc [1, 2]
A study by Mitchell et al [7] on welding of Ti64 by electron beam welding (EBW) suggested a slight increase in strength in the weld zone (HAZ and fusion zone (FZ)). This is reflected in the increase of the tensile strengths where the unwelded base metal yield strength (YS) of 941 MPa, ultimate tensile strength (UTS) of 983 MPa and elongation of around 13% compared to aswelded with YS around 960 MPa, UTS 1010 MPa but a slight reduction in elongation to 8.5%
The tensile properties, strain distribution, fracture mechanisms, and microstructure of electron beam welded (EBW) Ti-5Al-5V-5Mo-3Cr (Ti5553) in the aswelded condition were investigated by Sabol et al [17] in order to evaluate the weldability of this alloy [17]

Summary

Introduction

Titanium and its alloys are used in many different areas such as aerospace, automotive, sporting equipment, chemical, marine and medical due to their excellent high strength-to-weight ratio, good creep resistance, excellent corrosion resistance, good biocompatibility, etc [1, 2]. Typically CP Ti welds have coarse columnar grains in the fusion zones (FZ) compared with the heat affected zones (HAZ) and the base metal (BM) [2,3,4,5,6,7]. A study by Mitchell et al [7] on welding of Ti64 by electron beam welding (EBW) suggested a slight increase in strength in the weld zone (HAZ and FZ) This is reflected in the increase of the tensile strengths where the unwelded base metal YS of 941 MPa, UTS of 983 MPa and elongation of around 13% compared to aswelded with YS around 960 MPa, UTS 1010 MPa but a slight reduction in elongation to 8.5%. The microstructure was principally α-prime in the FZ and acicular α with α-prime in the HAZ

Metastable β and β alloys

Current investigations

Findings

Summary