The feasibility of applying the fluidized bed furnace to the solution and aging treatments of aluminum alloys was assessed by examining concerns such as the efficiency of heat treatments and delay of quenching, together with its merits such as the shortening of heat treatment and the possibility of high temperature heat treatments.

  It was concluded that this method realizes high efficiency of heat treatments, which is comparable to that attainable with the combination of a salt bath and oil bath. By suppressing the delay time within 20 to 30sec. after the removal of works from the fluidized bed furnace, no degradation in mechanical properties occurs. The allowable delay time is dependent on the work size. The solution treatment time can be shortened to 60min. or below. Good mechanical properties were obtained even with a short solution treatment time of 15min. depending on the size and thickness of the work. This also enables suppression of pore growth at the same time. In addition, high temperature heat treatment at around ternary eutectic temperatures was realized by precise temperature control, thereby realizing superior mechanical properties and shorter heat treatment time.

  In this study, lead-free Zn-Al-Sn solders for high-temperature applications were proposed using s-orbital energy level (ΔMk) in order to satisfy both the tensile strength of 200MPa and elongation of 5%. Promising compositions of alloys were Zn-4Al-7Sn, Zn-10Al-0.5Sn, and Zn-10Al-2Sn in mass% and their ΔMk values were 0.079, 0.080 and 0.089, respectively. Their ingots were produced and tensile tested at 293K in air. The proposed alloys showed tensile strength of 195 - 225MPa depending on the increment of ΔMk values, and elongation of 4.5 - 5.1%. Optimization of compositions on Zn alloys was found to be speedy and precisely achieved using the ΔMk parameter. The proposed alloys also showed liquidus temperatures of 645-700K, indicating that the high temperature lead-free solders can be applied for power semiconductor device packages, etc. In addition, contact angles of 33.8° and 73.5° at 973K in Ar stream were seen between Cu plate and the proposed alloys Zn-4Al-7Sn and Zn-10Al-0.5Sn, respectively, suggesting that the proposed alloys can be practically applied at high temperatures.

  The vertical-type tandem twin-roll caster is able to produce clad strips from molten alloys by single step. The caster consists of two twin roll casters arranged vertically. The base strip produced at the upper caster is led to the roll gap of the lower caster and the solidifying shell of the overlay alloy grown from the roll surface of the lower caster sandwiches the base strip and produced the clad strip. In the present study, a three-layered aluminum alloy clad strip of A4045/A3003/A4045 was fabricated. Microstructure observation and composition analysis under various magnifications from the optical microscopic-to transmission electron microscopic-order were performed. Both OM and SEM observations found fine solidification structure of both alloy strips. The joint interface was flat and no alloyed region was observed at the interface. A thin layer of about 1μm in thickness including neither Al-Mn base nor eutectic Si particles, was observed at the joint interface. Orientation analysis and chemical composition measurement using TEM and STEM-EDS revealed that the crystal orientation of thin layer took over that of each grain of A3003 and the composition was comparable to the α-Al matrix of A4045. This indicates that the thin layer was the solidified shell of A4045 grown epitaxially from the strip surface of A3003.