Friction surfacing (FS) is a solid state technology with increasing applications in the context of localized surface engineering. FS has been investigated mainly for producing fine grained coatings, which exhibit superior wear and corrosion properties. Since no bulk melting takes place, this process allows the dissimilar joining of materials that would be otherwise incompatible or difficult to deposit by fusion based methods. Several studies also emphasize its energy efficiency and low environmental impact as key advantages when compared with other alternative technologies. Main applications include the repair of worn or damaged surfaces through building up or crack sealing. It has also been applied to enhance surface properties at specific areas in the manufacturing of parts and tools. A wide range of materials combinations has been deposited by FS, mainly alloy and stainless steels. Aluminium, magnesium and titanium alloys have also been investigated, including the production of metal matrix composites. Starting with a brief introduction, this review presents a detailed description of the thermo-mechanical and microstructural transformations, as well as, process modelling approaches. The material combinations investigated so far and the effect of process parameters are also addressed. An overview of the main technologic and equipment 6.2. Pre-heating or cooling concepts .
The aim of this investigation was to study the influence of tool geometry on material flow during heterogeneous friction stir welding in 1 mm thick plates of AA 5182-H111 and AA 6016-T4 aluminium alloys. Two types of tool shoulders were used: a shoulder with a conical cavity and a scrolled shoulder. Pin-driven flow was predominant in welds produced with the conical cavity shoulder, which are characterized by an onion ring structure. The interaction between pin-driven and shoulder-driven flow is restricted to the crown of the weld, at the trailing side of the tool, and extends throughout the weld thickness, at the leading side. Although no onion ring structure was formed in welds done with the scrolled shoulder, extensive mixing of the base materials occurred in a plasticized layer flowing through the thickness around the rotating pin. Shoulder-driven flow is intense and continuous around the tool.
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