Hiroshi Tokisue

Bio: Hiroshi Tokisue is an academic researcher from College of Industrial Technology. The author has contributed to research in topics: Heat-affected zone & Welding. The author has an hindex of 5, co-authored 5 publications receiving 132 citations.

Mechanical Properties of Friction Surfaced 5052 Aluminum Alloy

Abstract: 5052 aluminum alloy used for substrate and consumable rod, was friction surfaced using a numerical controlled full automatic friction welding machine. Effects of the surfacing conditions on some characteristics of deposits were investigated. It was clearly observed that the circularly pattern appeared on the surface of deposit by the rotation of consumable rod. The deposit has a tendency to incline toward the advancing side further than center of deposit for the feed direction of consumable rod. This deviation accompanied the decrease of the rotational speed of consumable rod. The width of deposit increased with increasing friction pressure, and decreasing rotational speed of consumable rod. The thickness of deposit became thinner when the consumable rod was high revolution. The surfacing efficiency decreased with increasing friction pressure and rotational speed of consumable rod, but increased with increasing feed speed. Microstructure of the deposit was finer than that of the substrate and consumable rod. The softened area was recognized at 3 mm distance from the weld interface of substrate. The tensile strength of deposit increased with increasing friction pressure. The maximum tensile strength of deposits showed 88.8% of the base metal of substrate.

Mechanical Properties of 5052/2017 Dissimilar Aluminum Alloys Deposit by Friction Surfacing

Abstract: 5052 aluminum alloy plate used for substrate and 2017 aluminum alloy bar used for coating rod, both monolayer and multilayer friction surfacing were done using a numerical controlled full automatic friction welding machine. Effects of the surfacing conditions on structure and mechanical properties of both monolayer and multilayer deposits were investigated. It was clearly observed that the circular pattern appeared on the surface of both monolayer and multilayer deposits by the rotation of coating rod, and the interval of circularly pattern become narrower with increasing of the rotation of coating rod. The monolayer deposit has a tendency to incline toward right side (Retreating side) further than center of deposit for the feed direction of coating rod. And, the 2nd surfacing of multilayer deposit recognized to incline toward the 1 st deposit side. A little of incomplete welds was observed at both sides of monolayer deposit. The incomplete parts of welds 1 st deposit in multilayer deposit were disappeared by 2nd surfacing. Microstructures of both monolayer and multilayer deposits were finer than those of the substrate and coating rod. The deposition efficiency of 2nd surfacing in multilayer deposit showed higher value than that of the monolayer deposit. Hardness of both deposits showed higher value than that of the substrate and same value of coating rod. The softened area was recognized at 2.5 mm distance from the weld interface of substrate and coating rod. The tensile strength of multilayer deposit showed higher value than that of the monolayer deposit, and both deposits showed higher value than that of the substrate.

Some Characteristics of AZ31/AZ91 Dissimilar Magnesium Alloy Deposit by Friction Surfacing

Abstract: Monolayer friction surfacing was performed using a numerical controlled full automatic friction welding machine for AZ31 magnesium alloy plate used for substrate and AZ91 magnesium alloy casting bar used for consumable rod. Effect of the surfacing conditions on structures and mechanical properties of deposit were investigated. It was clearly observed that the circular pattern appeared on the surface of deposit by the rotation of coating rod. Microstructures of deposit showed finer structure than that of both base metals, and the cast structure was disappeared. Hardness of the deposit showed higher value than that of the substrate. Wear resistance of the deposit was improved in comparison with the substrate.

Electron Bean Weldability of Pure Magnesium and AZ31 Magnesium Alloy

Abstract: Pure magnesium and AZ31 magnesium alloy plates 4 mm in thickness were butt welded without addition of filler wire using a high voltage electron beam welding machine. Mechanical properties and microstructures of the welded joints were investigated. Regardless of the materials, the welded joints were almost free from welding defects and showed good bead appearance under appropriate welding conditions. The arcing phenomena tend to appear at low welding speed. Optimum beam current and welding speed were smaller than those for electron beam welded joints of aluminum alloys. Hardness in the fusion zone of the joints are nearly equal to those of the base metals. Microstructure on the fusion zone of pure magnesium joints was remarkably coarse, although the weld interface could not unambiguously detected. The fine crystal grains observed on the fusion zone of AZ31 alloy joints. Regardless of the welding conditions, both tensile strength and ductility of the joints show same value to those of the base metals, but the elongation of the joints are inferior to those of the base metals. From the tension test and impact test, pure magnesium joints fractured at the center of the fusion zone, but in case of AZ31 alloy joints, crack occurred at weld interface and it propagated through the fusion zone.

Additive manufacturing of an aluminum matrix composite reinforced with nanocrystalline high-entropy alloy particles

Abstract: In the present work, a metal-metal composite consisting of aluminum-magnesium alloy AA5083 matrix and nanocrystalline CoCrFeNi high-entropy alloy reinforcement particles in 12 vol% was successfully friction deposited in multiple layers. The layer interfaces or the reinforcement/matrix interfaces showed no brittle intermetallic formation – thanks to the inert nature as well as the high strength and hardness of the high-entropy alloy reinforcement particles. The composite showed significantly higher tensile and compressive strengths as compared to standard wrought-processed alloy AA5083-H112 and offered a much better combination of strength and ductility when compared to conventional aluminum matrix composites reinforced with ceramic particles. The current study establishes friction deposition as a viable technique for additive manufacturing of novel high-performance composite materials.

Interface evolution and bond strength when diffusion bonding materials with stable oxide films

Abstract: The effects of stable surface oxides on the interface morphologies and strengths of aluminium diffusion bonds are reviewed. Previous approaches, proposed to overcome problems with surface oxides when joining aluminium alloys and composites, are described and compared for both solid-state diffusion bonding and conventional transient liquid-phase diffusion bonding. Non-conventional joining methods, particularly the new method of temperature-gradient transient liquid-phase diffusion bonding and its capability of producing high-strength bonds reliably, also are considered. Copyright © 2001 John Wiley & Sons, Ltd.