Welding and Joining of Titanium Aluminides

Abstract:A new type of high temperature titanium alloy, BTi-6431S, has recently become the focus of attention as a potential material for aircraft engine applications, which could be used up to 700 • C. Pulsed laser welding was used to butt join the BTi-6431S titanium alloy in order to understand the feasibility of using fusion-based welding techniques on this material. The effect of laser energy on the microstructure and mechanical properties of the joints was investigated. The microstructural features of the joints were characterized by means of microscopy and X-ray diffraction. Tensile testing was conducted at both room temperature and high temperature to simulate potential service conditions. The results show that the microstructure of the laser welded joints consists of primary α phase and needle α' phase, while the microstructure of the heat affected zone consists of α, β, and needle α' phases. The tensile strength of the welded joints at room temperature was similar to that of the base material, despite a reduction in the maximum elongation was observed. This was related to the unfavorable microstructure in the welded joints. Nonetheless, based on these results, it is suggested that laser welding is a promising joining technique for the new BTi-6431S titanium alloy for aerospace applications.

Section: Mechanical Properties Of the Jointssupporting

confidence: 65%

Laser Welding of BTi-6431S High Temperature Titanium Alloy

Zeng

Oliveira

et al. 2017

“…The development of joining technologies has become an essential requirement for application of these alloys in replacing traditional metallic alloys in aerospace and automotive applications [3][4][5][6]. However, there are only a few reports regarding the techniques used to join TiAl alloys with other materials [6][7][8][9][10][11][12].…”

Section: Introductionmentioning

confidence: 99%

Joining of TiAl to Steel by Diffusion Bonding with Ni/Ti Reactive Multilayers

Simões

Ramos

Viana

et al. 2016

Dissimilar diffusion bonds of TiAl alloy to AISI 310 stainless steel using Ni/Ti reactive multilayers were studied in this investigation. The Ni and Ti alternating layers were deposited by d.c. magnetron sputtering onto the base materials, with a bilayer thickness of 30 and 60 nm. Joining experiments were performed at 700 and 800˝C for 60 min under pressures of 50 and 10 MPa. The effectiveness of using Ni/Ti multilayers to improve the bonding process was assessed by microstructural characterization of the interface and by mechanical tests. Diffusion bonded joints were characterized by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), electron backscatter diffraction (EBSD), transmission electron microscopy (TEM) and selected area electron diffraction (SAED), high resolution TEM (HRTEM) and Fast Fourier transform (FFT). The bonding interfaces are thin (approximately 5 µm thick) with a layered microstructure. For all joints, the interface is mainly composed of equiaxed grains of NiTi and NiTi 2 . The thickness and number of layers depends on the joining conditions and bilayer thickness of the multilayers. Mechanical characterization of the joints was performed by nanoindentation and shear tests. Young´s modulus distribution maps highlight the phase differences across the joint´s interface. The highest shear strength value is obtained for the joint produced at 800˝C for 60 min under a pressure of 10 MPa using Ni/Ti multilayers with 30 nm of bilayer thickness.

“…Conventional titanium alloys are continuously challenged by the operation at temperatures higher than 550 • C due to poor high temperature oxidation resistance and creep properties [2]. Whence, the investigations on the production, characterization, and joining of titanium alloys as titanium aluminides (TiAl), TiNi and Ti6Al4V, have increased during the last decades [5][6][7][8][9][10][11][12][13][14][15][16][17][18].…”

Section: Introductionmentioning

confidence: 99%

“…Dissimilar joints between titanium alloys are essential for their successful integration into high temperature aerospace and automobile applications combining unique properties as well as overcoming some disadvantages of these alloys [5]. For instance, the joining of TiNi and Ti6Al4V alloys is vital for the development of a shape memory alloy (SMA) adaptive serrated nozzle to aid noise reduction in next-generation gas turbine engines and the blade SMA actuator to enable in-flight rotor tracking in commercial and military helicopters [7,8].…”

Section: Introductionmentioning

confidence: 99%

Recent Progress in the Joining of Titanium Alloys to Ceramics

Simões

2018

The prospect of joining titanium alloys to advanced ceramics and producing components with extraordinary and unique properties can expand the range of potential applications. This is extremely attractive in components for the automotive and aerospace industries where combining high temperature resistance, wear resistance and thermal stability with low density materials, good flowability and high oxidation resistance is likely. Therefore, a combination of distinct properties and characteristics that would not be possible through conventional production routes is expected. Due to the differences between the coefficients of thermal expansion (CTE) and Young's modulus of metals and ceramics, the most appropriate methods for such dissimilar bonding are brazing, diffusion bonding, and transient liquid phase (TLP) bonding. For the joining of titanium alloys to ceramics, brazing appears to be the most promising and cost-effective process although diffusion bonding and TLP bonding have clear advantages in the production of reliable joints. However, several challenges must be overcome to successfully produce these dissimilar joints. In this context, the purpose of this review is to point out the same challenges and the most recent advances that have been investigated to produce reliable titanium alloys and ceramic joints. for next-generation aircraft turbine engines [1][2][3][4]. Though, the development of bonding techniques especially to successfully produce dissimilar joints is the key to overcoming the poor room-temperature ductility and fracture toughness of these alloys that limit these potential applications.The possibility of combining the extraordinary properties of these titanium alloys with other materials such as nickel-based superalloys, steel, or even ceramics through dissimilar bonding can allow the development of components not only with complex geometries but also with a combination of properties exceeding the limitations of these materials when used individually.Advanced ceramics have attractive properties, such as high wear resistance, high thermal stability as well as high thermal and electrical conductivities. It is known that some of the advanced ceramics like alumina, silicon nitride, and zirconia, are also well established in the electronics, aerospace, nuclear, and automotive industries [19,20]. However, their inherent brittleness, high cost, and high hardness limit the production of large and complex shape components. The successful application of these advanced ceramics depends strongly on the joining of these materials with metals. In addition, the possibility to combine properties as high wear resistance and high thermal stability with low density, high temperature properties, and excellent creep and corrosion resistance could enable the production of more advanced components that better meet the high requirements of several industrial sectors [21].The most suitable methods for bonding metals and ceramics and producing successful joints with appreciated properties are brazing , diffusion bonding...