Recent Advances in Friction-stir Welding Process and Microstructural Investigation of Friction Stir Welded Pure Titanium

Abstract

The aim of this work was to perform thermal characterization of commercially pure titanium in dry air to determine its oxidation kinetics and the structure of the oxide. The oxidation kinetics were determined thermogravimetrically under isothermal conditions in the temperature range 300 to 750 o C for 48 hours and the structure of the oxides was determined by differential thermal analyses and X-ray diffraction in the temperature range room temperature -1000 o C. The oxidation rate of titanium increased with increase in temperature. It was high in the initial stages of oxidation and then decreased rapidly with time, especially up to 600 o C. The kinetic laws varied between inverse logarithmic at the lower temperatures (300 and 400 o C) and parabolic at the higher temperatures (650, 700 and 750 o C). Evidences from X-ray diffraction and differential thermal analyses data revealed that the passive oxide film formed at room temperature crystallized into anatase at about 276 o C. The crystallized oxide formed in the range 276 -457 o C consisted of anatase, in the range 457 -718 o C consisted of anatase and rutile sublayers, and at temperatures beyond 718 o C consisted of a layer of pure rutile. Scanning electron microscopy observations reveled that the oxidized surfaces were crack-free and the surface roughness increased steadily with oxidation temperature.Keywords: Titanium, oxidation kinetics, oxide film, structure. Cinética de oxidação de um titânio puro comercial RESUMOO objetivo deste trabalho foi de realizar uma caracterização térmica de um titânio puro comercial para estudar sua cinética de oxidação e seus produtos de corrosão formados em atmosfera de ar seco em função da temperatura. A cinética de oxidação foi determinada por termogravimetria em condições isotérmicas entre 300 e 750 o C por 48 horas e os óxidos formados foram caracterizados por análise térmica diferencial e difração de raios-X entre a temperatura ambiente até 1000 o C. A cinética de oxidação aumenta com a temperatura e é muito rápida nos primeiros instantes, diminuindo rapidamente com o tempo, especialmente até 600 o C. As leis cinéticas variaram entre a logarítmica inversa nas temperaturas mais baixas (300 e 400 o C) e a parabólica nas temperaturas mais altas (650, 700 e 750 o C). As análises por difração de raios-X e análise térmica diferencial mostraram que a cristalização do filme passivo de óxido, formado naturalmente à temperatura ambiente, ocorre aproximadamente a 276 o C. A estrutura do óxido é composta de anatásia cristalina entre 276 e 457 o C, anatásia e rutilo entre 457 e 718 o C, e somente rutilo acima de 718 o C. Observações por microscopia eletrônica de varredura revelaram que as superfícies oxidadas não apresentam fissuras e que suas rugosidades aumentam uniformemente com a temperatura de oxidação.Palavras-chave: Titânio, cinética de oxidação, filme de óxido, estrutura.

Research on the friction stir welding of Titanium Grade 1

“…In all samples has been reported the occurring of ultrafine SZ microstructure with grain size about 5µm. What is important, the peak temperature in friction stir welding process of titanium can exceeds the temperature of its allotropic transformation what can lead to formation of serrated grain boundaries in the stir zone, as the result of the β → α transformation during cooling stage after formation of joint [11,19]. On the other hand, the allotropic transformation α → β, occurring in the heating stage of friction stir welding process and promoted by severe plastic deformation in the stir zone causes the dynamic restoration in this area [20,21].…”

“…FSW technique is the solid-state welding process, widely used for joining light alloys, such as aluminum and magnesium alloys. The process of joining is based on friction between workpieces and the rotating tool, which generates heat leading to plasticizing of material to be welded [9,[11][12][13]. The movement of rotating tool along the edges of two workpieces causes mixing of plasticized material, and as the result the creation of joint between them [9,12].…”

Friction spot lap joining of the anodized aluminium alloy 6061 with high-density polyethylene sheets

“…Laser, ultrasonic, friction lap welding (Liu et al, 2014) and friction spot joining (Abdullah and Hussein, 2018;Goushegir et al, 2014) were earlier used in joining the different materials. The friction stir welding process exhibited a small residual stress and low heat input as compared with conventional welding methods (Kim et al, 2017). The welding process occurrs by generating frictional heat between the rotating tool and specimen of a solid state case (Nam et al, 2016).…”

On Dynamic Recrystallization During Friction Stir Processing of Commercially Pure Ti and Its Influence on the Microstructure and the Mechanical Properties

“…Titanium and its alloys are known for their high specific strength, high heat resistance, and high resistance to erosion and corrosion [1][2][3][4][5][6][7][8][9][10][11][12][13][14]. Friction Stir Processing (FSP) was derived from friction stir welding (FSW) in 2000 and was first reported by Mishra et al [15].…”