Abstract: A process for making a work piece from a ?-type titanium alloy material includes subjecting the ?-type titanium alloy material to cold working with controlling the reduction rate thereof to vary the reduction rate depending on a position across a plain direction of the ?-type titanium alloy material, and then subjecting the ?-type titanium alloy material to an aging treatment.

Abstract: A process for making a work piece from a ?-type titanium alloy material includes subjecting the ?-type titanium alloy material to cold working with controlling the reduction rate thereof to vary the reduction rate depending on a position across a plain direction of the ?-type titanium alloy material, and then subjecting the ?-type titanium alloy material to an aging treatment.

Abstract: A process for making a plate composed of a ?-type titanium alloy material for a golf club head face includes subjecting the ?-type titanium alloy material to cold working with controlling the reduction rate thereof to vary the reduction rate depending on a position across a plain direction of the ?-type titanium alloy material, and then subjecting the ?-type titanium alloy material to an aging treatment so as to build up a hardness distribution across the plain direction of the ?-type titanium alloy material.

Abstract: A method of manufacturing a curved metal plate includes pressing a metal plate made of a plate material selected from titanium or titanium alloy with a die segment that forms thereon a convex surface curving in at least one direction and at least one recess, with a first side of the metal plate in contact with the convex surface, thereby curving the metal plate along the convex surface while allowing a part of the plate material on the first side of the metal plate to intrude into the at least one recess under pressure, thus forming at least one rib on the first side of the metal plate.

Abstract: A golf club head showing good ball bouncing performance is provided with good cold workability and age hardenability.

Abstract: A titanium alloy is provided wherein metal boride is uniformly crystallized and/or precipitated in the matrix. The heating temperature in the finishing hot working is set smaller than the &bgr; transus temperature by not less than 10° C., thereby causing the matrix to include an equiaxial &agr; structure in a rate of not less than 40 vol %. This titanium alloy has excellent properties, i.e., high rigidity, ductility and fatigue strength, which are all required for structural components, and therefore can be widely applied to a mechanical component such as an engine of an automobile, a structural component in an aircraft as well as a component for a high speed rail vehicle.

Abstract: A method of manufacturing a curved metal plate includes pressing a metal plate made of a plate material selected from titanium or titanium alloy with a die segment that forms thereon a convex surface curving in at least one direction and at least one recess, with a first side of the metal plate in contact with the convex surface, thereby curving the metal plate along the convex surface while allowing a part of the plate material on the first side of the metal plate to intrude into the at least one recess under pressure, thus forming at least one rib on the first side of the metal plate.