T. Komazaki

Bio: T. Komazaki is an academic researcher. The author has contributed to research in topics: Friction stir welding & Welding. The author has an hindex of 6, co-authored 10 publications receiving 824 citations.

Three defect types in friction stir welding of aluminum die casting alloy

Abstract: For different tool plunge downforces, the optimum FSW conditions of aluminum die casting alloy were examined. The higher the tool plunge downforce is, the wider the range of the optimum FSW conditions is. The following three different types of defects are formed, depending on the FSW conditions. (1) A large mass of flash due to the excess heat input; (2) cavity or groove-like defects caused by insufficient heat input; and (3) cavity caused by the abnormal stirring. As for the abnormal stirring, it is clearly seen that the shape of the top part on the advancing side in the stir zone is completely different. For this type of defect, the effect of the tool plunge downforce is small, though the size of the defect due to insufficient heat input significantly decreases with the increasing downforce.

Improvement of mechanical properties of aluminum die casting alloy by multi-pass friction stir processing

Abstract: An improvement in the mechanical properties was accomplished due to the microstructural modification of an aluminum die casting alloy by multi-pass friction stir processing (MP-FSP), which is a solid-state microstructural modification technique using a frictional heat and stirring action. The hardness of the MP-FSP sample is about 20 Hv higher than that of the base metal. The tensile strengths of the MP-FSPed specimens were significantly increased to about 1.7 times versus that of the base metal. This is due not only to the disappearance of the cold flake in the base metal, but also to a structural refinement, such as uniform distribution of Si particles. Thus, the application of the MP-FSP is a very effective method for the mechanical improvement of aluminum die casting alloys.

Role of zinc coat in friction stir lap welding Al and zinc coated steel

Abstract: AC4C cast Al alloy and Zn coated steel were successfully lap welded using friction stir welding technology. Full strength joints could be obtained and the joints fractured at Zn coated steel base metal side, while Al alloy and unzinced steel could not be welded in the same welding conditions. The joining mechanism and the role of Zn coat on friction stir lap welding of Al alloy and Zn coated steel were put forward. The intervention of Zn coat promoted the formation of Al–Zn low melting point eutectic structure at the interface, which significantly improved the weldability of Al and steel.

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

Friction stir processing technology: A review

Abstract: Friction stir processing (FSP), developed based on the basic principles of friction stir welding (FSW), a solid-state joining process originally developed for aluminum alloys, is an emerging metalworking technique that can provide localized modification and control of microstructures in near-surface layers of processed metallic components. The FSP causes intense plastic deformation, material mixing, and thermal exposure, resulting in significant microstructural refinement, densification, and homogeneity of the processed zone. The FSP technique has been successfully used for producing the fine-grained structure and surface composite, modifying the microstructure of materials, and synthesizing the composite and intermetallic compound in situ. In this review article, the current state of the understanding and development of FSP is addressed.

The role of friction stir welding tool on material flow and weld formation

Abstract: In this investigation an attempt has been made to understand the mechanism of friction stir weld formation and the role of friction stir welding tool in it. This has been done by understanding the material flow pattern in the weld produced in a special experiment, where the interaction of the friction stir welding tool with the base material is continuously increased. The results show that there are two different modes of material flow regimes involved in the friction stir weld formation; namely “pin-driven flow” and “shoulder-driven flow”. These material flow regimes merge together to form a defect-free weld. The etching contrast in these regimes gives rise to onion ring pattern in friction stir welds. In addition to that based on the material flow characteristics a mechanism of weld formation is proposed.