The present invention provides a simple, cost effective and hassle-free method and apparatus for modifying the surface grain structure of the material, thereby providing a material with multi-modal grain structure having high strength and good formability. The present invention uses a single step processing technique known as submerged static friction stir processing for modifying the surface grain structure of the material, thereby generating a multi-modal grain structure. In the present invention since the working material is completely immersed in the coolant, this maintains the working temperature of the system. Further the present invention does not involve long processing steps and do not need any specialized equipments.

A method for producing a plate heat exchanger and the plate heat exchanger, particularly a soldered aluminium plate heat exchanger. In the method, a heat exchanger block is provided having a plurality of partition plates and edge strips arranged between the partition plates. A connection device is provided to be mounted on the heat exchanger block. A planar region for securing the connection device to the heat exchanger block is provided with at least one welded weld bead by means of a first weld. The connection device is welded onto the weld bead by means of a second weld. The welding method used for the first weld is a friction stir welding method.

Provided are an effective and simple surface-modifying method for prolonging the life of a steel structure made of a steel material having a high sulfur (S) content, and a steel structure having a life prolonged by the surface-modifying method. A surface-modifying method for forming a friction stir region on the surface of a steel material by friction stir processing, wherein a sulfur (S) content of the steel material is 200 ppm or more.

In some examples, techniques for enhancing a corrosion resistance of a component are provided. In some examples, the component includes a granular metallic material. A friction stir processing operation is performed on the material. The friction stir processing operation comprises passing a rotating head of a friction stir welding tool through a surface thickness of the granular metallic material in a treatment path.

During friction stir spot welding, a controller executes a temperature holding control in which the controller controls a rotation driving unit so that a rotational speed of a tool is set to a value which is equal to or lower than a predetermined rotational speed at which a temperature of the tool is regarded as being equal to a welding temperature of lapped portions, and in which the controller controls a displacement driving unit to increase and reduce a welding pressure or plunge depth of the tool so that the temperature of the tool is held in a predetermined set range.

A method of forming a vibration-damped aluminum article is provided. The method includes forming a groove in a surface of an aluminum substrate, the groove having a groove depth which is less than 50% of a thickness of the aluminum substrate. The method further includes placing metal oxide nanoparticles in the groove to form an unmixed composite. The method further includes friction stir processing the unmixed composite to form the vibration-damped aluminum article. The friction stir processing includes at least two passes over the unmixed composite. The vibration-damped aluminum article includes a surface nanocomposite portion and an aluminum alloy portion. The metal oxide nanoparticles are substantially free of metal carbides, metal borides, and carbon nanomaterials.

Intended is to improve the corrosion resistance of an overlay used in a nuclear power plant, and to reduce dissolution of cobalt from an overlay. The corrosion and wear resistant overlay 7 is formed along a surface of a base 2 by laser lamination modeling, and is configured from a plurality of metal layers 1a, 1b, 1c, and 1d of a Co-base alloy. The thickness of carbide eutectics that precipitate in the metal layers 1a, 1b, 1c, and 1d is the largest in the metal layer 1a closest to the base 2, and is gradually smaller in the metal layers 1b, 1c, and 1d farther away from the base 2. The intensity of the laser beam applied to form layers by laser lamination modeling is adjusted so that the carbide eutectics that precipitate in at least the outermost metal layer 1d have a controlled size of 10 μm or less.

A method of performing friction stir spot welding of a plurality of steel plates, includes the steps of: friction stirring a spot welding portion of the plurality of steel plates by pressing a tool against the spot welding portion while rotating the tool, to plasticize the spot welding portion by friction heat; cooling the spot welding portion to cause martensitic transformation to occur in the spot welding portion, after the step of friction stirring the spot welding portion; and tempering the spot welding portion by the friction heat by re-pressing the tool against the spot welding portion while rotating the tool, after the step of cooling the spot welding portion.

Shear assisted extrusion processes (ShAPE) for forming Metal-NCCF extrusions are provided. The processes can include: using a die tool, applying a rotational shearing force and an axial extrusion force to a feedstock material comprising a metal and NCCF (NanoCrystalline Carbon Films); and extruding a mixture comprising the metal and NCCF through an opening in the die tool to form the Metal-NCCF extrusion. ShAPE feedstock materials are provided that can include a metal and NCCF. Conductive solid material mixtures are provided that can include a metal and a NCCF. Portions of the metals and NCCF of the material mixtures can have an isotropic crystallographic orientation. Assemblies relying in part on conductivity can include: a conductive solid material mixture that includes: a metal; and a NCCF.

A continuous feed method for friction stir processing includes continuously feeding a tubular material having a first grain microstructure from a bulk source into a processing chamber, and forcing the tubular material between a die and a textured end portion of a mandrel as the tubular material is advanced through the chamber. The continuous feed method further includes rotating the mandrel within the tubular material while forcing the tubular material across the textured end portion to friction stir process the tubular material and transform a structure of the tubular material from the first grain microstructure to a second grain microstructure. The second grain microstructure is a finer equiaxed grain microstructure than the first grain microstructure. The method further includes converting the tubular material having the second grain microstructure into a stiffened sheet form.