There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

비만아 부모의 돌봄 경험: q 방법론

A review on selective laser sintering/melting (SLS/SLM) of aluminium alloy powders: Processing, microstructure, and properties

A review of selective laser melting of aluminum alloys: Processing, microstructure, property and developing trends

Friction stir welding (FSW) is a widely used solid state joining process for soft materials such as aluminium alloys because it avoids many of the common problems of fusion welding. Commercial feasibility of the FSW process for harder alloys such as steels and titanium alloys awaits the development of cost effective and durable tools which lead to structurally sound welds consistently. Material selection and design profoundly affect the performance of tools, weld quality and cost. Here we review and critically examine several important aspects of FSW tools such as tool material selection, geometry and load bearing ability, mechanisms of tool degradation and process economics.

Review: friction stir welding tools

Ti-alloys, particularly TiAl, are becoming attractive for the use in the production of high-temperature components such as turbine blades and exhaust valves, owing to their low density. However, these components may not be cost-effectively cast totally from TiAl alloys and casting defects may occur in investment casting of these complex parts. Other manufacturing technologies, such as machining, cannot be economically employed in these very hard and brittle materials. Production of bi-material or even multi-material TiAl components can therefore offer an alternative fabrication route provided that the joining and joint properties of these materials are well understood. In this study, the diffusion bondability and joint characteristics of TiAl and Ti–6Al–4V alloys were studied. These two different materials were joined by using various bonding parameters. Metallographic investigations were conducted for characterization of the interface region of these dissimilar joints. Furthermore, the mechanical behavior of the bond interface was evaluated by shear testing. Both results on the microstructural and mechanical characterization provided the optimum bonding conditions for the production of TiAl–Ti6Al4V hybrid joints.

Microstructural and mechanical characterization of diffusion bonded hybrid joints

Formation of weld defects in cold metal transfer arc welded 7075-T6 plates and its effect on joint performance

The present study considers the effect of strength mismatch on the fracture behaviour of diffusion bonded joints between commercially pure (CP) Ti and Ti-6Al-4V (Ti64), including dissimilar joints and sandwich structures with strength undermatching and overmatching. The aim of the investigation is to determine the influence of the interlayer thickness (for both higher and lower strength interlayers) and the bond quality on the deformation behaviour and fracture toughness of the joints. The influence of mechanical heterogeneity (strength mismatch) on the fracture behaviour of the interface in dissimilar joints was also investigated. Round bars of CP Ti and Ti64 having a diameter of 40 mm were diffusion bonded as dissimilar butt joints and sandwich structures containing lower strength (undermatching) and higher strength (overmatching) interlayers of different thicknesses. Round transverse tensile specimens and standard four point bend (single edge notch bend) specimens were extracted from the joints...

Fracture behaviour of diffusion bonded titanium alloys with strength mismatch

Nowadays, there is an increasing demand for the use of joining dissimilar metals in various industrial applications owing to the economic benefits and better joint performance. Ferritic stainless steel grades is a good alternative for austenitic ones in several applications as they display higher ductility and strength as well as better corrosion resistance in chloride environments. However, the poor ductility and low impact toughness of ferritic stainless-steel welded joints limit their wide-spread application. Thus, the demand for joining dissimilar ferritic and austenitic stainless steels is ever increasing in several engineering applications in various industries such as nuclear power plants, coal fired boilers, automobile manufacturing industry, chemistry and petro-chemistry industries, etc. Therefore, successful joining of these two different types of stainless steel grades using conventional fusion welding methods is rather important. In this study, the weldability of AISI 430 ferritic and AISI 304 austenitic steel plates using gas metal arc welding and the effect of heat input on microstructure and the mechanical properties were investigated. For this purpose, AISI 430 and AISI 304 plates with a thickness of 5 mm were joined using different heat input values. The microstructures evolved in the weld region of the joints and their mechanical properties were determined by detailed optical microscopy investigations, micro-hardness measurements and tensile tests. Thus, the influence of the heat input on the weldability of these two different stainless-steel plates using gas metal arc welding was also studied.

Microstructure and mechanical properties of gas metal arc welded AISI 430/AISI 304 dissimilar stainless steels butt joints

The present study focuses on the applicability of friction stir welding to pure Pb plates. The joint performances are evaluated by optical microscopy, microhardness measurements, notch impact tests and three point bending tests. The effects of the tool rotational speed (1500, 2000 and 2500 rev/min) and welding speed (72, 100 and 125 mm/min) on the joint performance are determined. The results indicate that the welded joints exhibit similar or higher mechanical properties than those of the base material. Optimal joint performance was achieved with a rotational speed of 1500 rev/min and welding speed of 100 mm/min.

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Gürel Çam

Papers

Microstructural and mechanical characterization of diffusion bonded hybrid joints

Formation of weld defects in cold metal transfer arc welded 7075-T6 plates and its effect on joint performance

Fracture behaviour of diffusion bonded titanium alloys with strength mismatch

Microstructure and mechanical properties of gas metal arc welded AISI 430/AISI 304 dissimilar stainless steels butt joints

Microstructural and mechanical properties of friction stir welded pure lead