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The Formation of Al3Ti Intermetallic compound at the junction interface of Titanium-Aluminum diffusional Coupling by Means of Diffusional Annealing Process
Dr M. Tavoosi, S. Arjmand,
Volume 37, Issue 1 (Journal of Advanced Materials-Spring 2018)
Abstract

In this study, the formation of the Al3Ti intermetallic compound at the junction interface of aluminum-titanium was investigated during deposition and annealing. The results illustrated that during the deposition process, one thin layer of Ti3Al2 intermetallic compound was created at the junction interface. During the annealing at 550 °C, this layer was transformed to the  Al3Ti intermetallic phase and the layer growth occurred. By performing annealing at higher temperatures, the growth rate of Al3Ti intermetallic layer was increased; at the same time, the formation of Kirkendall cavities and  coupling in the cavities and fragmentation of diffusional coupling from the junction with aluminum were observed


Development of Al-Ti-N Composite Coatings on Commercially Pure Ti Surface by Tungsten Inert Gas Process
S. Arjmand, M. Tavoosi,
Volume 39, Issue 3 (Journal of Advanced Materials-Fall 2020)
Abstract
The present work aims to modify surface properties of pure Ti by development of Ti-Al-N intermetallic composite coatings. In this regard, tungsten inert gas (TIG) cladding process was carried out using Al 1100 as filler rod with Ar and Ar+N2 as shielding gases. Phase and structure of the samples were investigated by X-ray diffraction (XRD) technique, optical microscopy (OM) and scanning electron microscopy (SEM). Hardness values and corrosion behavior of the obtained coatings were also compared using Vickers microhardness tester and potentiostat, respectively. The results showed that composite structure containing Al3Ti, Ti3Al2N2 and Ti3Al intermetallic compounds could be formed on the surface of pure Ti. Amounts of brittle phases and welding defects at the titanium-coating interface were least by welding under pure Ar shielding. Despite the increasing amount of structural defects such as porosity and non-uniformity under Ar+N2 shielding, the prepared coatings had higher hardness (more than 100 HV) and corrosion resistance (more than twice) compared with those obtained under Ar shielding.
 
Evaluating the Effect of the Number of Welding Passes on Microstructure, Hardness and Residual Stress of Ti-Al-Si Composite Coatings
S. Arjmand, G. H. Akbari, G. R. Khayati,
Volume 39, Issue 4 (Journal of Advanced Materials-Winter 2021)
Abstract
The purpose of the present work is to investigate the influence of the number of weld-passes on microstructure, hardness and residual stresses of composite coatings composed of Ti-Al-Si intermetallic compounds. In this regard, surface coating of pure Ti was carried out using one and two passes of tungsten inert gas (TIG) welding with an Al filler alloy (grade 4043). Phase and structural evaluations of the coatings were investigated by X-ray diffraction, optical and scanning electron microscopies. microhardness and residual stress values of the coatings were measured using ASTM E384-HV device and the Sin2ψ method, respectively. The results showed that as the number of welding passes increased or the dilution ratio decreased, the volume fraction of Ti5Si3-Al3Ti intermetallic phases within the fusion zone increased and the volume fraction of martensite phase in the heat affected zone decreased. As a result, the average hardness value of the coating increased to be about 130 % compared to that of the pure Ti substrate. The tensile residual stresses at the center line of fusion zone were 165 ± 30 and 210 ± 35 MPa for the coatings prepared in one and two welding passes, respectively.

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