Hiroshi Tokisue

Friction and wear properties of aluminum-particulate graphite composites

Abstract Aluminum alloy matrix composites containing 3, 6 and 9 wt.% particulate graphite were produced and their friction, wear, and tensile properties were determined. The composite fabrication process consisted of adding nickel-coated graphite particles into a partially solidified and vigorously agitated Al-7%Si-1%Mg alloy, followed by remelting and casting into ingots. The coefficients of friction and wear of the as-cast and liquid-forged composites were determined by a Falex lubricant test machine. It was found that the friction and wear properties of both as-cast and liquid-forged alloys considerably improved with addition of graphite. While the tensile strength and ductility of composites containing 3% graphite were comparable with those of the matrix, increasing graphite content reduced these properties.

Impact Properties of TIG Welded AZ31 Magnesium Alloy Joints

Magnesium and its alloys are the lightest among the metallic materials which are in common use, having a high strength-to-weight ratio along with an excellent machinability and a high damping capacity.　Because of these characteristics, nowadays they are applied to various structural parts such as aircraft, automobiles, optical and electronic instruments, industrial robot components. 　TIG welded joints of AZ31 magnesium alloy has high joint efficiency which can be obtained by the selection of optimum welding conditions. If the welded joints of magnesium alloy are applied to the structure materials, it is very important not only the strength of under static load but also the strength of under dynamic load. However, there is only few report about impact properties of welded AZ31 magnesium alloy joints. In this research, AZ31 magnesium alloy plates 6 mm in thickness were welded on butt welding of square groove without root gap and filler wire using TIG welding process. AZ31 magnesium alloy was carried out at various welding conditions. The effects of welding conditions and notch location on impact properties were studied. Impact values of welded joints were nearly equal to those of the base metal, regardless of welding current. In case of the notched specimens of welded joints, crack initiation energy showed slightly lower than crack propagation energy, regardless of notch location. But, unnotched specimens of welded joints, crack initiation energy showed remarkably high value than crack propagation energy. This means, crack initiation energy spent the large amount of total absorbed energy.