Abstract: This paper is concerned with pressure welding, which has been known as a main bonding mechanism during the cold and warm formings such as clad extrusion or bundle extrusion/drawing. Bonding characteristics between the Cu and Al plates by pressure welding are investigated focusing on the weak bonding. Experiments are performed at the cold and warm temperatures ranging from the room temperature to 200°C. The important factors examined in this work are the welding pressure,
pressure holding time, surface roughness, and temperature. A bonding map, which can identify the bonding criterion with a weak bonding strength of 1MPa , is proposed in terms of welding pressure and surface roughness for the cold and warm temperature ranges.
Abstract: For the preparation of multi-crystalline Si ingot, an EMC (Electromagnetic Continuous Casting) technique using a segmented Cu cold crucible under a high frequency alternating magnetic field was utilized. Numerical and experimental works were systematically carried out in order to optimize the effect of Joule heating and electromagnetic pressure. A Si melt of 5.5 cm height was able to be kept non-contact with the crucible wall when the induction coil current of 970 A was applied. A
segmented graphite crucible, which was attached at the upper part of the cold crucible, was introduced to enhance significantly the heating efficiency of Si melt keeping non-contact condition.
Abstract: With the usage of Al-Cu bimetals to connect aluminum and copper in power distribution systems growing persistently, efforts to mitigate the mechanical, electrical and electrochemical degradation are widely made. The explosive bonding technology has been considered as a countermeasure for the degradation. In this paper, electrochemical analysis and optical microscopic observation are carried out in order to compare the corrosion resistivity of the explosion type bimetal to the commonly used compression type bimetal. In particular, the effect of anions in the interfacial electrolyte on corrosion susceptibility was also investigated. The results show that the explosive bonding technology can prevent the interfacial corrosion caused by the formation of crevices and pits as well as by galvanic potential difference between aluminum and copper.
Abstract: The formation of nitrogen gas pores is affected by various factors such as solidification sequence, solubility of nitrogen, cooling rate, melt pressure, nitrogen content etc. Nitrogen porosity in Fe-16Cr-3Ni-9Mn austenitic stainless steel solidifying to primary d-ferrite that can cause nitrogen gas pores was examined. And also the effect of nitrogen content, cooling rate and melt pressure on nitrogen porosity was investigated.
Abstract: Metal foam was produced by the Melt Foaming Method. In this foaming process, the
surface tension and the viscosity of molten Al (recycled waste Al) and Mg alloy (Az91) that were measured respectively by the ring method and the rotational method are the most important two factors. They surface tension and the viscosity were investigated in the temperature range of about 600-900°C and the effects of the additional surface-active elements were investigated at the about 640°C. The measured surface tension of the molten recycled Al and Az91 decreased linearly with the increasing temperature of Ar gas (99.999%) and SF6+CO2 (1:100) atmosphere. The effect of surface-active elements is a decrease of the surface tension and an increase of the viscosity. The optimal conditions for the foam metal manufacturing are needed the low surface tension and the high viscosity. It is possible that the optimal conditions of the surface tension and the viscosity can be
obtained through controlling the amount of adding surface-active elements.
Abstract: The porous materials, such as glass wool or foam, are generally used to attenuate noise. The most fundamental acoustic property of these porous materials is their sound absorption coefficient. The purpose of this paper is sintered fiber and porous materials sound absorption properties investigated. Sound absorption properties of sintered Al fiber has over 0.7 of sound absorption coefficient with 800-2000Hz frequency for 0.6 relative density and 10mm thickness. NRC (noise reduction coefficient) is 0.73. Metal foam have good sound absorption rate at 2000 ~ 4000Hz.