METALLURGICAL CHARACTERISTICS OF WELDED TITANIUM ALLOYS

MATEC Web of Conferences

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.

International Journal of Scientific Research in Science, Engineering and Technology, 2020

Titanium and its alloys are the most commonly and most widely used due to its significant properties like good biocompatibility , good tensile strength , low density , and good creep property up to 300 degrees centigrade .It is used in the major engineering fields like civil engineering , nuclear engineering , aerospace engineering etc., but the welding of titanium in industries has become a major challenging objective to the fabricators because, a lot of titanium alloys are found in the form of sheets , problem arises mainly while fabricating the space crafts , marine bodies , jet engine’s where the ends are need to be joined through welding with a similar or dissimilar metals and titanium possess to have a very high tendency to oxidize at higher temperatures .As Titanium becomes highly reactive to chemicals in its environment. In regular air, welding contaminates titanium with carbides, nitrides, and oxides that make the weld and HAZ (heat-affected zone) brittle, resulting in lower fatigue resistance and notch toughness. so, In order to get a perfect weld it is very important to avoid the molten metal to the exposure of atmospheric air , which will lead to porosity and results into a poor welding conditions or welding defects. This paper reviews the different methods of welding titanium and its alloys.

Titanium alloys are widely used in many fields such as the automotive, aerospace and chemical industries. In some applications, Titanium alloys are needed for use with particular welding methods. These are GTAW, GMAW .In this study, Titanium Grade-2 (Cp-Ti) plates were welded using GTAW welding. Tensile and flexural tests were applied to the welded samples. The microstructure and SEM images of main material and welded regions were studied and microhardness measurements were performed.Tensile and flexural strengths of GTA welded samples were higher than pure Ti welded samples. The microhardness values of the weld-zone of GTA welded samples were higher than the pere Ti welded samples welding zone. In microstructure and SEM investigations, oxide structures and the splashes of molten metal appearing like drops were identified.

Welding in the World, 2019

In this study, it is reported that the diffusion welding of αtitanium and (α + β) titanium alloys with aluminium has been carried out by applying sufficient compression to the welded samples to give a high level of plastic deformation in the Al layers sandwiched between layers of titanium alloy with a moderate surface finish. Both metals are active in the air; such diffusion processes can take place under vacuum. However, we report, that high quality welds were achieved at temperatures between 610 and 630 o C under ambient air atmosphere, without the use of vacuum or reducing atmospheres. The resulting microstructures and intermetallic phases were characterized using scanning and transmission electron microscopy and EDX microanalysis. This showed that under the welding parameters selected, Ti diffused across the interface into Al and Al into Ti, since the protective Al2O3 thin film on the surface of aluminium layer has been disrupted due to the Al layer plastic deformation. Impact tests of welds gave relatively high energy impact values.

Scripta Materialia, 1996

JOM, 2018

This article presents some recent results from fusion welding of titanium alloys with interlayers. Without an interlayer, the CP Ti weld typically results in comparable hardness across the weld and base material (BM). However, for a alloys, near-a alloys and a + b alloys, the fusion zone (FZ) and heat-affected zone (HAZ) show high hardness compared with the BM. Inversely, b alloys have FZ and HAZ with lower hardness compared with BM. Under loading, the presence of areas with high or lower hardness could affect the load distribution across the weldments. Post-welding heat treatment (PWHT) is sometimes employed to minimise or avoid this situation. However, for large-size components, PWHT is not practical. In this investigation, we show that by selecting a proper interlayer the above issues can be minimised; hence, PWHT may not be necessary, leading to cost reduction and process efficiency.

2011

In this work, three welding programs for orbital gas tungsten arc welding (GTAW), previously developed, were used, using pulsed current and increasing speed (#A), constant current (#B) and pulsed current and decreasing current (#C). One of these should be used for the propulsion system of the Satellite CBERS (China-Brazil Earth Resources Satellite). Welded joints using tubes of commercially pure titanium were obtained with these procedures, which were characterized by means of mechanical and metallographic tests. The obtained results showed that the three welding procedures produce welded joints free of defects and with adequate shape. Although small differences on mechanical properties and on microstructure have been observed, the three welding programs attained compatible results with international standards used in the aerospace segment. The welding program #B, due to the reduced heat input used, was considered to obtain slightly advantage over the others.

Metallurgical and Materials Transactions, 2009

Microstructure and mechanical properties of gas-tungsten-arc (GTA)-welded Ti-15V-3Cr-3Sn-3Al alloy in direct current electrode negative mode are characterized. The thermal profile was measured during welding with continuous current (CC) and pulsed current (PC) at different frequencies. A single-step postweld aging of the welded samples at subtransus temperature was attempted to study precipitation of alpha phase. Two different morphologies of alpha phase are observed along with a partitioning of alloying elements into the two phases. Processing conditions for higher strength are identified and correlated with the thermal profile. Microstructure changes due to postweld heat treatment were characterized.

Guide to best practice -1999

The Paton Welding Journal, 2016