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.

The present invention provides a simple, single step and time efficient method and apparatus for developing ultrafine grained microstructure stainless steel having enhanced wear resistance, corrosion resistance, biocompatibility, cellular response and hem-compatibility for bio-implant applications. The processed stainless steel showed 50% reduction in corrosion, high resistance against localised pitting and 50% reduction in wear in simulated body fluid. In addition, the processed steel demonstrated better cell viability, significantly lower platelet adhesion and plasma adsorption signifying high thrombo-resistance and thereby making it highly desirable for bio-implant applications. The present invention eliminates the long processing steps and do not need any specialized equipments and also eliminates the post process treatments.

A joint processing method includes: a friction stir welding step for forming a joint in a plate by friction stir welding a groove in the plate; a cold working step for cold working the joint under cold working conditions such that a grain size in the joint is not more than a grain size of an aluminum alloy in the groove prior to the friction stir welding step; and a solution heat treatment step for, subsequent to the cold working step, performing solution heat treatment of the plate.

A method for welding a first component to a second component. The method includes providing a first component including a first alloy, providing a second component including a second alloy, heating the first component, and solid state welding the second component to the first component.

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.

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 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.

The present invention is 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 is formed along a surface of a base by laser lamination modeling, and is configured from a plurality of metal layers of a Co-base alloy. The thickness of carbide eutectics that precipitate in the metal layers is the largest in the metal layer closest to the base, and is gradually smaller in the metal layers farther away from the base. 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 have a controlled size of 10 m or less.

A method for forming a metal matrix composite (MMC) structure includes forming an assembly including at least two blocks of a primary phase material sharing an interface at which a secondary phase material is disposed. The assembly has a length, a width, and a thickness. The method also includes clamping the assembly to at least one of urge the at least two blocks toward each other or maintain the at least two blocks at a predetermined position. Also, the method includes passing a rotating friction-stir pin along the interface from the front edge to the rear edge. The friction-stir pin has a mixing length extending at least the width of the assembly, and passing the friction-stir pin along the length of the assembly disperses the secondary phase material into the primary phase material and welds the at least two blocks together.

An object is to provide a friction stir welding method and apparatus that provide sufficient strength and good welding workability by advantageously eliminating plastic flow deficiency generated as a result of insufficient heating of workpieces.

In friction stir welding for steel sheets (3, 3) as workpieces, a pair of facing rotary tools (1, 15) are inserted into a non-welded part from both one surface side and the other surface side of the steel sheets (3, 3), the rotary tools move in a welding direction while rotating, and in addition, a preheating process for heating steel sheets (3, 3) is performed by heating means (5) provided in front of the rotary tools(1, 15). The configuration of the pair of facing rotary tools (1, 15) and the surface temperature, area, position, and so forth of a heated region in the preheating process are strictly controlled.