Shigetoshi Jogan

Bio: Shigetoshi Jogan is an academic researcher. The author has contributed to research in topics: Welding & Friction welding. The author has an hindex of 8, co-authored 25 publications receiving 1100 citations.

Microstructural evolution of 6063 aluminum during friction-stir welding

Abstract: The microstructural distribution associated with a hardness profile in a friction-stir-welded, age-hardenable 6063 aluminum alloy has been characterized by transmission electron microscopy (TEM) and orientation imaging microscopy (OIM). The friction-stir process produces a softened region in the 6063 Al weld. Frictional heating and plastic flow during friction-stir welding create fine recrystallized grains in the weld zone and recovered grains in the thermomechanically affected zone. The hardness profile depends greatly on the precipitate distribution and only slightly on the grain size. The softened region is characterized by dissolution and growth of the precipitates during the welding. Simulated weld thermal cycles with different peak temperatures have shown that the precipitates are dissolved at temperatures higher than 675 K and that the density of the strengthening precipitate was reduced by thermal cycles lower than 675 K. A comparison between the thermal cycles and isothermal aging has suggested precipitation sequences in the softened region during friction-stir welding.

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.

Aluminum vessel and manufacture thereof

Abstract: PROBLEM TO BE SOLVED: To obtain a joint which does not heat the inner part of a vessel to a high temp. regarded as giving the adverse effect to the contents and has high closeness and does not develop a root crack by joining the vessel main body and a cover body in a specific range to the ratio of the depth of a fused joining part and the width of the fused joining part. SOLUTION: For example, a part of a vessel body composed of Al or an Al alloy is notched and a cover body 2 is fitted to join the vessel body 1 and the cover body 2. Then, the ratio of the depth D of a fused joining part 3 and the width W of the fused joining part 3, i.e., an aspect ratio (D/W) is made to 1-5. At the time of using a slab laser beam as a high density heat source, a condition, in which the aspect ratio at the joining part is made to >=1, is easily found by executing a simply test and the aluminum closed vessel usable as a case for a high density battery of a high performance lithium ion secondary battery, etc., excellent in impact resistance can be manufactured by executing a simple test run.

Jointing method of container

Abstract: PROBLEM TO BE SOLVED: To provide a jointing method of a metal container by which a high yield is obtained, and a high sealability between a container body and a lid material is obtained, even though they are made by press molding, without making the inside of the container high temperature, at the time of jointing the press-molded container body by high-density heat-source welding. SOLUTION: At the time of jointing airtightly a lid body A to the opening of a press-molded container body B by high-density heat-source welding, the lid A, wherein a width W1 of a central part of a lid body taper part (height T) is approx. the same size as a width W2 of an opening of the container body, and the taper part is made out of 30 to 75% of a thickness H of the lid body at an angle α of 5 to 30 degrees, is fitted in and successively welded by the high-density heat-source.

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