Indian Welding Journal

T. Venugopal ¹, K. Prasad Rao ¹

Affiliations
1 Department of Metallurgical and Materials Engineering, IIT Madras, IN

Abstract

The earliest reference of the use of frictional heat for solid phase welding and forming appeared over a century ago. After 50 years, in 1941 the friction surfacing was developed. After an other 50 years, the recent development friction stir welding (FSW) was invented. In this review an account is given on the research that has been carried out on FSW. The process established itself as a prominent technology for joining conventionally un-weldable metals. In this paper the basics of the process, joint configurations, microstructures, thermal analysis, residual stress, distortion and materials flow behavior are discussed. The recent development of the process FSW of composites is also discussed.

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K. Prasad Rao ¹

Affiliations
1 Department of Metallurgical Engineering, Indian Institute of Technology Madras, Chennai, IN

Abstract

This paper presents the advances in the welding processes. It presents the trends in the application of special welding processes such as micro welding, microwave welding, friction stir welding, etc. Wherever pertinent, the joining of advanced materials such as intermetallics, biomaterials, ceramics, plastics, composites, etc is discussed.

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K. Prasad Rao ¹, N. Ramanaiah ¹, B. Vamsikrishna ¹

Affiliations
1 Department of Metallurgical & Materials Engineering Indian Institute of Technology Madras, Chennai, IN

Abstract

The paper deals with an intention of solving HAZ problems through manipulating fusion zone chemistry and microstructure. Grain refiners such as Sc, Ti+B and Zr have been added to fusion zone through the AA5356 filler metal. The results indicated that the maximum refinement in the weld microstructure and consequent reduction in cracking susceptibility in alloy AA6061 can be achieved using AA5356 filler metal with 0.5% Sc addition.

Keywords

Grain Refinement, Welds, Aluminium Alloy, Partially Melted Zone, Haz Cracks, Liquation.

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K. Srinivasa Rao ¹, K. Prasad Rao ¹

Affiliations
1 Department of Metallurgical and Materials Engineering Indian Institute of Technology Madras, Chennai-600036, IN

Abstract

Partially Melted Zone (PMZ) of aluminium alloy welds is an important region and requires careful attention. This is mainly because PMZ in these materials is weak link in the weldments and is significantly affected by welding parameters. Microstructure changes in PMZ are related not only to welding heat input and techniques, but also depend on the initial thermal history of alloy (for example, whether it is in T-4, T-6 or T-87 condition etc). Interestingly not many detailed studies are available in this respect. In the present work effect of prior thermal temper and welding techniques mainly continuous and pulsed current Gas Tungsten Arc Welding (GTAW) on the PMZ behaviour of AA2219 and AA6061 alloys were studied. Susceptibility to liquation was high in T-6 temper of 2219 alloy compared to that of T-87 temper. Susceptibility to liquation is high in T-6 temper of AA6061 alloy compared to that of T-4 temper and has been attributed to more amount of silicon rich eutectic at the grain boundaries of PMZ. Pulsed current technique was found to improve the resistance to the susceptibility to liquation in PMZ of AA2219 and AA6061 alloys and is due to the possible reduction in the peak temperature.

Keywords

Partially Melted Zone, GTA Welds, Continuous Current, Pulsed Current, Prior Thermal Temper, Liquation, Al-Alloy.

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Ch. Radhakrishna ¹, K. Prasad Rao ²

Affiliations
1 Defence Metallurgical Research Laboratory, Hyderabad, IN
2 Indian Institute of Technology, Madras, IN

Abstract

When section thickness, increases more than 5mm, high energy density process like Electron Beam Welding (EBW) is advantageous than conventional Gas Tungsten Arc Welding (GTAW). The inherent vacuum conditions of EBW process make welding of Ti6Al4V more appropriate. However, it is generally observed that certain alpha/beta alloy of titanium welds made by EBW tend to exhibit lower values of toughness compared to their base metal counterparts (1) which is attributed to the alpha prime martensitic structure formed due to higher weld cooling rates.

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