Abstract: Recently, magnesium alloy is in the limelight as ECological material with high ability of recycling and lightweight property. Especially, because of outstanding properties as a structural material, the magnesium alloy is in great demand. Under these circumstances, the technical researches and developments of welding process for magnesium alloy welding have great significance to expand industrial application of magnesium. In magnesium alloy welding, arc welding process is generally used. However, heat input by the welding arc affects the magnesium alloy plates, and as the result it makes wide heat affected zone and large distortion of the welded joint. As one of the possible means to improve quality of the welded joint, application of laser welding process may be recommended. However, the low boiling point of magnesium generates some weld defects, such as porosity and solidification cracking. Furthermore, the small laser beam diameter is very sensitive to edge preparation in butt joint. Accordingly, application of laser/ arc hybrid welding process to magnesium alloy welding was proposed. The laser/ arc hybrid welding process is a new process combining the laser beam and the arc as welding heat source. The laser beam and arc influence and assist one another. By application of hybrid welding, synergistic effects are achievable, and disadvantage of the respective processes can be compensated. In this study, welding of AZ31B magnesium alloy thin plates using YAG laser/ TIG arc hybrid welding process was investigated. In order to confirm the properties of the welded joints, tensile testing was performed.
Abstract: Two kinds of aluminum alloys have been used as lap joint in FSW. Experiments are
selected to observe metal flow by metallurgical procedures. One is for the effect of probe type and pre-friction time on metal flow at start point. Another is for the effect of probe type on metal flow for stable traveling stage. Thermal analysis also has been carried out.
Abstract: Friction Stir Welding is the most remarkable welding technology that has been
invented and developed in last decade. It made it possible to join a number of light metals that were previously believed difficulties to get reliable welds without defects including distortion. This summarizing report tried to clarify the recent trend of this novel technology in Japan. It reveals that Japan industry may have the most active potentials of developments in the world, particularly in the field of practical applications.
Abstract: This paper describes the features and characteristics of plasma induced in the pulsed YAG laser welding of Al-Mg alloys in air and argon atmospheres. In the air environment, the identified spectra are atomic lines of Al, Mg, Cr, Mn, Fe and Zn, and singly ionized Mg line, as well as strong molecular spectrum of AlO, MgO and AlH. It has been confirmed that the resonant lines of Al and Mg were strongly self-absorbed. These facts have shown that the laser-induced plasma is relatively a low temperature and high density metallic vapor. The intensities of molecular spectra of
AlO and MgO are different each other depending on the power density of laser beam. Under the low power density irradiation condition, the MgO band spectrum is predominant in intensity, while the AlO spectrum became much stronger with the increase in high power density. This was attributed by the great difference in boiling point and vaporization energy of Al and Mg. In argon atmosphere the band spectra of MgO and AlO completely vanished, but AlH molecular spectra is detected clearly. The hydrogen source is presumably the hydrogen solved in the base metal,
absorbed water on the surface oxide layer, or H2 and H2O in the shielding gas.
Abstract: Welding between ADC12 and SS400 was successfully performed by friction stir diffusion process. The experiments were conducted by a machining center with a cemented carbide tool and welding conditions, such as a rotating speed, welding speed and position of the tool, were optimized. By plunging the rotating tool into the interface with offset, ADC12 and SS400 were welded above 2000 rpm of the rotating speed at the welding speed of 50mm/min. Tensile strength was evaluated for the welded specimens. The specimens fabricated above 5000rpm in the rotating speed were fractured at the weld zone and showed relatively low tensile strength. The specimens, on the other hand, made between 2000 and 4000 rpm were fractured in the portion of the base aluminum alloy. Achievement of more than 100% in joint efficiency was indicated in the present friction stirring process.
Abstract: Many researches for friction welding of aluminum with either carbon steel or stainless steel have been carried out. From those results, it is concluded that the greatest problem is the formation of brittle intermetallic compounds at weld interface. However, it is not clearly demonstrated the effect of friction welding parameters on the formation of intermetallic compounds. This research purposes are to evaluate the formation of intermetallic compounds and to investigate the effect of friction welding parameters on the strength of welded joint. For these purposes, A6061 aluminum alloy and S45C carbon steel were used with a continuous drive vertical friction welding machine. Tensile test results revealed that the maximum tensile strength was achieved at extremely short friction time and high upset. The joint strength reached 92% of the tensile strength of A6061 base metal. Tensile strength of friction welding was increasing with increasing upset pressure when friction time 1sec. However, tensile properties were deteriorated with increasing friction time. It was observed that the amount of formed intermetallic compound was increasing with increasing friction time at weld interface. Partly formed intermetallic compound on weld interface were identified when friction time 1sec. However, intermetallic compound layer were severely developed with longer friction time at weld interface. It was concluded that intermetallic compound layer deteriorated the tensile properties of weld joints.
Abstract: A composite microstructure consisted of µm-scale Ta-rich solid solution particles
distributed in the bulk metallic glass matrix was successfully obtained by injection casting of the (Cu 60Zr 30Ti 10) 95Ta 5 alloy into a copper mold. The (Cu 60Zr 30Ti 10) 95Ta 5 bulk metallic glass matrix composite shows compressive strength of 2320 MPa and, in particular, a significantly improved plastic strain to failure of about 14.5%. The remarkable ductility improvement in the (Cu 60Zr 30Ti 10) 95Ta 5 composite could be explained by the presence of the highly ductile Tarich particles.
Abstract: Microcontact printing of hydrophobic OTS (Octadecyl-Trichloro-Silane) material was made on various substrates, and finely patterned CdS thin film has been fabricated by CBD (Chemical Bath Deposition) method. In the preliminary experiment, it is confirmed that the size of colloid particle and roughness of surface of CdS thin film are increased with increase of pH, fabrication time and temperature. The optimum condition for the selective deposition of CdS film pattern using the SAM with microcontact printing was determined to be pH 10, temperature of 75°C, deposition time of 15 minute. Various patterns of different shape of CdS thin film were
fabricated uniformly and satisfactorily in large area by the conditions determined in the present work. The stoichiometric composition of CdS was confirmed to be 1:1 by EDS and XPS.
Abstract: The ionic valence of Ti changed with electrorefining process of Ti in a bath equi-molar mixture of NaCl-KCl containing TiCln (n=2 or 3); The average valence was about 2.3 initially, and became about 2.1 after electrolysis. The cathodic current efficiency was getting better with electrolysis. It should be necessary to maintain the average ionic valence lower for efficient electrolysis in the molten salt. The dominant Ti ion and its electrode reaction changed with the addition of NaF-KF in the molten salt; The average valence shifted from about 2 to about 3, and the total amount of Ti in the bath decreased. The result indicates the disproportionation reaction: 3Ti2+ = Ti + 2Ti3+ is induced by the fluoride addition. The quantity of electricity for Ti deposition changed consequently, and the purity of the Ti deposit was also affected.