Takenori Hashimoto

Bio: Takenori Hashimoto is an academic researcher from Subaru. The author has contributed to research in topics: Welding & Friction stir welding. The author has an hindex of 19, co-authored 96 publications receiving 1408 citations. Previous affiliations of Takenori Hashimoto include Showa Denko.

Microtexture in the friction-stir weld of an aluminum alloy

Abstract: In order to characterize plastic flow during friction-stir welding, the microtextures in a friction-stir weld of the precipitation-hardened aluminum alloy 6063 have been analyzed by orientation imaging microscopy (OIM). The base-material plate has a Goss orientation. The weld center region, except for the upper surface, takes a typical shear texture component with two types of orientations. The orientations have a pair of common {111} and 〈110〉 parallel to the cylindrical pin surface and transverse direction of the plate, respectively. The typical texture component is also observed around the weld center on the midsection, although it rotates about the plate normal direction. A microtexture analysis after postweld heat treatment has suggested that dynamic recrystallization during friction-stir welding generates the recrystallized grains at the weld center.

Precipitation sequence in friction stir weld of 6063 aluminum during aging

Abstract: The precipitation sequence in friction stir weld of 6063 aluminum during postweld aging, associated with Vickers hardness profiles, has been examined by transmission electron microscopy. Friction stir welding produces a softened region in the weld, which is characterized by dissolution and growth of the precipitates. The precipitate-dissolved region contains a minimum hardness region in the aswelded condition. In the precipitate-dissolved region, postweld aging markedly increases the density of strengthening precipitates and leads to a large increase in hardness. On the other hand, aging forms few new precipitates in the precipitate-coarsened region, which shows a slight increase in hardness. The postweld aging at 443 K for 43.2 ks (12 hours) gives greater hardness in the overall weld than in the as-received base material and shifts the minimum hardness from the as-welded minimum hardness region to the precipitate-coarsened region. These hardness changes are consistent with the subsequent precipitation behavior during postweld aging. The postweld solution heat treatment (SHT) and aging achieve a high density of strengthening precipitates and bring a high hardness homogeneously in the overall weld.

Friction stirring joining method

Abstract: PROBLEM TO BE SOLVED: To obtain a high grade joined product free of welding defects, in friction stirring welding which performs butt-joining of two joining members, by inserting a rotating probe into the abutting part between the two members, moving the probe as inserted, thereby softening the part in contact with the probe through frictional heat and stirring it. SOLUTION: An auxiliary material 20 for joining, which is provided with a planar positioning part and a successively provided flange part having a T-shaped cross section, is arranged in the manner that the positioning part is interposed in the abutting part 3 of the joining members 1, 2 and that the flange part crosses over the abutting part 3 as well as paralleling to the face of the probe inserting side of the joining members 1, 2. The probe 12 is inserted in the manner that it is in contact with the flange and the positioning part of this auxiliary material, softening these parts and the joining members 1, 2 together by frictional heat, and butt-joining the members while the base material of the softened flange part of the auxiliary material is filled in a gap 4 formed in the abutting part 3 of the joining members.

Friction stirring welding method

Abstract: PROBLEM TO BE SOLVED: To provide a friction stirring welding method that quickly softens members to be joined, that prevents the members from being tucked up and that thereby enables a welded product to have a superior joined condition, in joining and integrating cross-sectionally circular members at a planned weld zone in the circumferential or the longitudinal direction SOLUTION: Two cross sectionally circular members 1, 1 to be joined are abutted on each other, with a rotary probe 13 inserted into this abutted part, a probe which is projectingly provided freely rotatably as one unit with a rotor 11 on the axial line of its shoulder 12 The members 1, 1 to be joined are rotated so that the probe 13 successively passes through the abutted part, with the probe inserted, in the manner that a part A on the side of the moving direction of the members at the shoulder 12 of the rotor 11 is pressed against the members, and also in the state that a part B2 on the opposite side in the rotating direction of the members is floated above the surface of the members COPYRIGHT: (C)1999,JPO

Friction agitation joining method, method for manufacturing joined butted members, and friction agitation joining apparatus

Abstract: In the friction agitation joining method according to the present invention, two plate-shaped joining members different in thickness, or a first joining member (1) and a second joining member (2), are butted against each other with a level difference formed at upper surface sides thereof. A rotating probe (42) of the joining tool (40) is inserted into the butted portion (3) of said first and second joining members (1,2) from the upper surface sides thereof. Joining-direction front sides of the first joining member (1) and the second joining member (2) with respect to the probe inserted position is pressed by a first front pressing roller (11) and a second front pressing roller (11), respectively, from the upper surface sides thereof. Furthermore, joining-direction lower sides of the first joining member (1) and the second joining member (2) with respect to a probe inserted position from said upper surface sides is pressed by a first lower pressing roller (21) and a second lower pressing roller (22), respectively, from the upper surface sides thereof. In this state, the butted portion (3) is joined by the friction agitation joining method.

Friction Stir Welding and Processing

Abstract: Friction stir welding (FSW) is a relatively new solid-state joining process. This joining technique is energy efficient, environment friendly, and versatile. In particular, it can be used to join high-strength aerospace aluminum alloys and other metallic alloys that are hard to weld by conventional fusion welding. FSW is considered to be the most significant development in metal joining in a decade. Recently, friction stir processing (FSP) was developed for microstructural modification of metallic materials. In this review article, the current state of understanding and development of the FSW and FSP are addressed. Particular emphasis has been given to: (a) mechanisms responsible for the formation of welds and microstructural refinement, and (b) effects of FSW/FSP parameters on resultant microstructure and final mechanical properties. While the bulk of the information is related to aluminum alloys, important results are now available for other metals and alloys. At this stage, the technology diffusion has significantly outpaced the fundamental understanding of microstructural evolution and microstructure–property relationships.

Friction stir welding of aluminium alloys

Abstract: The comprehensive body of knowledge that has built up with respect to the friction stir welding (FSW) of aluminium alloys since the technique was invented in 1991 is reviewed The basic principles of FSW are described, including thermal history and metal flow, before discussing how process parameters affect the weld microstructure and the likelihood of entraining defects After introducing the characteristic macroscopic features, the microstructural development and related distribution of hardness are reviewed in some detail for the two classes of wrought aluminium alloy (non-heat-treatable and heat-treatable) Finally, the range of mechanical properties that can be achieved is discussed, including consideration of residual stress, fracture, fatigue and corrosion It is demonstrated that FSW of aluminium is becoming an increasingly mature technology with numerous commercial applications In spite of this, much remains to be learned about the process and opportunities for further research a

A process model for friction stir welding of age hardening aluminum alloys

Abstract: In the present investigation, a numerical three-dimensional (3-D) heat flow model for friction stir welding (FSW) has been developed, based on the method of finite differences. The algorithm, which is implemented in MATLAB 5.2, is provided with a separate module for calculation of the microstructure evolution and the resulting hardness distribution. The process model is validated by comparison with in-situ thermocouple measurements and experimental hardness profiles measured at specific time intervals after welding to unravel the strength recovery during natural aging. Furthermore, the grain structure within the plastically deformed region of the as-welded materials has been characterized by means of the electron backscattered diffraction (EBSD) technique in the scanning electron microscope (SEM). Some practical applications of the process model are described toward the end of the article.