Deformation behavior in the extrusion of a aluminum square-channel bar has been analyzed experimentally. 1070 aluminum, commercial pure lead and Pb-1.5mass%Sb alloy in which several fine aluminum (99.99%) wires were buried along the extrusion direction were used as working materials. Channels with a section 10mm wide, 10mm high and 1mm thick were extruded with a container of 30mm in diameter (extrusion ratio 25.5). 1070 aluminum was extruded at 400°C and others at room temperatures. Following results are obtained: (1) The extrusion load is affected little by the location of die exit. (2) As the bottom side of the channel departs from the center of die, the extrudate curves more heavily toward the open side of the channel. (3) Metal flow in extrusion of the channel bar consists of two steps. At the first step, the cross-sectional shape of plastic region changes from a circle (the section of container) to an ellipse and at the second, from the elliptic section to the shape of the die hole. Only the location of plastic region in sections changes with die hole location, its shape and dimension are hardly affected. (4) For the dies and subpress used in this work, the major axis and ellipticity of plastic region on the boundary between the first and second deformation steps are 13.8mm and 0.91-0.92, respectively.

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Deformation behavior in the extrusion of an aluminum square-channel bar has been analyzed using a simple model. Based on the previous experimental results, following principal assumptions are used in the proposed analytical model. (1) Metal flow in the container consists of two steps: the cross-sectional shape of the plastic region changes from a circle (the section of container) to an ellipse at the first step and from the ellipse to the shape of die hole at the second step. (2) The relative location of the elliptic plastic region to die hole is fixed independently of die hole location on the die face. (3) The partial extrusion ratio at any part of die hole is equal to the total extrusion ratio. Analysis results are as follows: (1) The shape and dimension of the elliptic plastic region in second step are determined unequivocally by the dimension of die hole. (2) Analysis results of metal flow as well as the shape and dimension of the plastic region are in good agreement with the experimental results.

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Mechanically alloyed ceramic particles (Si, AlN, Al₂O₃ or SiC; 0.4-1μm in diameter; 15vol%)/aluminum composite were machined by dry turning using sintered tungsten-carbide tools and sintered diamond ones with different contents of Co as a binder. In both kinds of tools, the tool wear was uniquely related to the cutting distance, and its amount did not depend on the content of Co. Despite such an apparent similarity in the wear behavior for both kinds of tools, the amount of wear in the latter tools was much smaller than that in the former ones. The main factor determining the amount of tool wear was not the macroscopic (average) hardness of tools and alloys, but the hardness of ceramic particles involved in them; tool wear and hence cutting resistance decrease remarkably in case that the particle hardness in tools exceeds that in work materials.

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Mg-10mass%Gd and Mg-10mass%Dy alloys have high strength at high temperatures and exhibit good ductility. In this study, 1 or 2mass%Y or Nd was added to these binary alloys in order to increase high temperature strength and reduce the material cost, and the effect of the third alloying elements on their aging characteristics and high temperature tensile properties were investigated. Additions of Y or Nd to Mg-10mass%Gd or Dy alloys promote remarkable precipitation hardening by aging at high temperatures. Nd addition is found to be very effective to increase strength. It is clear that the Mg-10mass%Gd-2mass% Nd alloy exhibits the highest strength among investigated alloys and its strength is superior to that of the conventional heat resistant magnesium and aluminum alloys at temperatures higher than 200°C.

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In this study, Mg-10mass%Gd or Dy-2 or 3mass%Nd alloys containing zirconium as a grain refinement agent were melted for the purpose of further improvements of various properties. Aging characteristics and tensile properties up to 350°C of these alloys were investigated. Hardness at peak-aging becomes higher by the additions of 2 or 3mass%Nd and Zr, and pronounced age hardening is shown up to 275°C in Mg-Gd alloys and up to 250°C in Mg-Dy alloys. The remarkable age hardening is found to be caused by the precipitation of the metastable β"-phase with a D0₁₉ Crystal structure based on the results obtained by a transmission electron microscope. The Mg-10mass%Gd-3mass%Nd-Zr alloy has the highest strength in all examined alloys, and its ultimate tensile strength at 200 and 250°C are 310MPa and 300MPa respectively. Furthermore, specific strength of the Mg-10mass%Gd-3mass%Nd-Zr alloy at 250°C is 155MPa/(Mg/m³) and is higher by 30MPa/(Mg/m³) than that of the WE54A alloy. The Mg-Dy alloys are inferior to the Gd-bearing alloys in strength, but exhibit more ductility.

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Wrought magnesium alloy AZ31 was friction welded to magnesium alloy castings AZ91 using a brake type friction welding machine. Microstructure and mechanical properties of friction welded joint were investigated. Microstructures of the first weld zone are quite similar to those of the second weld zone. A fine grain structure is observed on the side of alloy AZ91 near the weld interface, while on the heat-affected zone of alloy AZ31, a modified fiber structure is observed along the flow direction of burr. The hardness at the weld interface is higher than that of the base metals. In the case of alloy AZ91, the hardness in heat-affected zone is higher than that in the base metal, and in the case of alloy AZ31, it is nearly equal to that of the base metal. The tensile strength of joints welded at a friction pressure between 50MPa and 60MPa is 90% to 106% of the castings. However the elongation of welded joints is inferior to that of alloy AZ91.

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