T. Mohandas

Bio: T. Mohandas is an academic researcher from Defence Metallurgical Research Laboratory. The author has contributed to research in topics: Welding & Heat-affected zone. The author has an hindex of 14, co-authored 18 publications receiving 937 citations.

Recent developments in stainless steels

Abstract: This article presents an overview of the developments in stainless steels made since the 1990s. Some of the new applications that involve the use of stainless steel are also introduced. A brief introduction to the various classes of stainless steels, their precipitate phases and the status quo of their production around the globe is given first. The advances in a variety of subject areas that have been made recently will then be presented. These recent advances include (1) new findings on the various precipitate phases (the new J phase, new orientation relationships, new phase diagram for the Fe–Cr system, etc.); (2) new suggestions for the prevention/mitigation of the different problems and new methods for their detection/measurement and (3) new techniques for surface/bulk property enhancement (such as laser shot peening, grain boundary engineering and grain refinement). Recent developments in topics like phase prediction, stacking fault energy, superplasticity, metadynamic recrystallisation and the calculation of mechanical properties are introduced, too. In the end of this article, several new applications that involve the use of stainless steels are presented. Some of these are the use of austenitic stainless steels for signature authentication (magnetic recording), the utilisation of the cryogenic magnetic transition of the sigma phase for hot spot detection (the Sigmaplugs), the new Pt-enhanced radiopaque stainless steel (PERSS) coronary stents and stainless steel stents that may be used for magnetic drug targeting. Besides recent developments in conventional stainless steels, those in the high-nitrogen, low-Ni (or Ni-free) varieties are also introduced. These recent developments include new methods for attaining very high nitrogen contents, new guidelines for alloy design, the merits/demerits associated with high nitrogen contents, etc.

Microwave Processing of Materials and Applications in Manufacturing Industries: A Review

Abstract: The main focused aim of developing new processing and manufacturing technologies are to reduce production or manufacturing costs, processing times, and to enhance manufactured product properties. The developed processing techniques should be widely acceptable for all types of materials including metal matrix composites, ceramics, alloys, and fiber reinforced plastics. Microwave materials processing is emerging as a novel processing technology which is applicable to a wide variety of materials system including processing of MMC, FRP, alloys, ceramics, metals, powder metallurgy, material joining, coatings, and claddings. In comparison to the conventional processes, microwave processing of materials offers better mechanical properties with reduced defects and economical advantages in terms of power and time savings. The present review work focuses mainly on global developments taking place in the field of microwave processing of materials and their relevant industrial applications.

Effect of welding processes on tensile properties of AA6061 aluminium alloy joints

Abstract: The present investigation is aimed at to study the effect of welding processes such as GTAW, GMAW and FSW on mechanical properties of AA6061 aluminium alloy. The preferred welding processes of these alloys are frequently gas tungsten arc welding (GTAW) and gas metal arc welding (GMAW) due to their comparatively easier applicability and better economy. In this alloy, the weld fusion zones typically exhibit coarse columnar grains because of the prevailing thermal conditions during weld metal solidification. This often causes inferior weld mechanical properties and poor resistance to hot cracking. Friction stir welding (FSW) is a solid phase welding technique developed primarily for welding metals and alloys that heretofore had been difficult to weld using more traditional fusion techniques. Rolled plates of 6 mm thickness have been used as the base material for preparing single pass butt welded joints. The filler metal used for joining the plates is AA4043 (Al-5Si (wt%)) grade aluminium alloy. In the present work, tensile properties, micro hardness, microstructure and fracture surface morphology of the GMAW, GTAW and FSW joints have been evaluated, and the results are compared. From this investigation, it is found that FSW joints of AA6061 aluminium alloy showed superior mechanical properties compared with GTAW and GMAW joints, and this is mainly due to the formation of very fine, equiaxed microstructure in the weld zone.

Friction welding – critical assessment of literature

Abstract: Friction welding is now well established as a means of joining many different types of materials, because it has proved itself to be a reliable and economical way of producing high quality welds. The present paper introduces different friction welding processes, their advantages and shortcomings. The history of friction welding and typical applications are also reviewed. In the context of friction welding, a number of subjects, such as frictional behaviour, joining mechanism, interface temperature and heat generation, still exist, where different concepts for explanation of the physical mechanisms have been proposed by different investigators. To clarify some inconsistencies in the interpretation of the friction welding process, a thorough review and critical assessment of the literature associated with this process is attempted.