This study has been carried out to investigate into the influence of solidification conditions mold on the structure and mechanical properties of Al-5wt%Mg alloy by metallic mold casting. The percentage of equiaxed grain of Al-5wt%Mg alloy castings increased both when pouring temperature decreased and when the low part or bottom of metallic mold was cooled. The hardness was checked and showed that hardness of outside in the castings was higher than that inside, and that it is the highest at the pouring temperature of $680^{\circ}C$. The castings had the highest U.T.S. and elongation when the bottom of metallic mold was cooled. At the same pouring temperature, the structure of castings was changed as the position of cooling parts of metallic mold was varied. When the castings were solidified through cooling of the bottom of the metallic mold, the morphology of Fe intermetallic compound has tendency to change to a Chinese script and the U.T.S. and elongation of Al-5wt.%Mg alloy castings was increased.

Solderability, interfacial reaction and mechanical properties of joint between Sn-Bi-Ag base solder and Cu-substrate were studied. Solders were subjected to aging treatments to see the change of mechanical properties for up to 30 days at $100^{\circ}C$, and then also examined the changes of microstructure and morphology of interfacial compound. Sn-Bi-Ag base solder showed about double tensile strength comparing to Pb-Sn eutectic solder. Addition of 0.7wt%Al in the Sn-Bi-Ag alloy increase spread area on Cu substrate under R-flux and helps to reduce the growth of intermetallic compound during heat-treatment. According to the aging experiments of Cu/solder joint, interfacial intermetallic compound layer was exhibited a parabolic growth to aging time. The result of EDS, it is supposed that the soldered interfacial zone was composed of $Cu_6Sn_5$.

The 8 mm dia: Sn-38%Pb eutectic alloy rods were produced by use of the horizontal continuous casting process with the heated mold and chill cast process. The cast rods were rolled into 2.0${\sim}$0.5 mm thick plates and structural and mechanical properties were examined. The results revealed that the plates produced by the continuous casting process with the heated mold show much higher superplasticity at ambient temperature (1550% elongation at 0.5mm thick plate and 0.5mm/min strain rate) than the plates procuced by chill cast process (630% elongation). Such a high superplasticity of the continuous cast plates is due to the high-quality plates free from any inside and surface defects with fine and uniform distribution of eutectic phases.

The purpose of this study is to improve hardness and wear resistance of high strength yellow brass by adding Fe, Cr, Mn, Si and Ni. Results showed that NiO, $FeCr_2O_4$ and intermetallic compound $Mn_5Si_3$ were produced when Ni, Fe-Cr and Mn-Si were added to the yellow brass. The hardness and wear tests showed the best results with the presence of the product precipitates and intermetallic compound. The calculation of relative wear resistance by volume fraction of each phases showed that the relative wear resistance of $Mn_5Si_3$ had the highest value, that of ${\beta}$ phase had the lowest. Observation of the worn surface showed that the main wear mechanism were found to be the abrasive wear, and also showed that the wear is caused by mechanical failure at the early stage.

Fabrication of high strength Mg-Li-Al alloys by squeeze casting was established by the stabilization of melt and mold temperatures, applied pressure and the refining method. The entrapment of inclusions during pouring was prevented using 30 ppi alumina foam filter. The as-cast microstructure consists of a mixture of ${\alpha}$ and ${\beta}$ phases including AILi and $MgLi_2$, Al particles, which are distributed in the ${\beta}$ matrix. The grain sizes of gravity and squeeze casting alloys were 288 ${\mu}m$ and 207 ${\mu}m$ respectively. The addition of Al in Mg-Li alloys promoted the formation of second phase particles, which were adjusted to optimize the properties of Mg-Li-Al alloys. The Mg-10wt%Li-5wt%Al alloy after heat treatment at $350^{\circ}C$ for 1 hour showed the maximum hardness value. This is due to the facts that the amounts of ${\alpha}$ and ${\beta}$ phases and their distributions are dependent upon the solution treatment temperature, and that the amounts of AILi and $MgLi_2Al$ particles are dependent upon the Al content.

The effect of wheel surface condition on solidification behavior of Al-Cu ribbon was investigated in order to establish extreme levels of heat extraction. The condition of wheel surface was changed either by heating the wheel surface up to $200^{\circ}C$ or by coating boron nitride(BN) onto the the rim of a wheel. Heating the wheel surface up to $200^{\circ}C$ improved the wetting behavior between the molten metal and the rotating wheel, leading to an increase in the ratio of columnar structure to the entire thickness of Al-4.3wt%Cu and Al-33.2wt%Cu ribbons. For Al-4.3wt%Cu ribbon, assuming one grain as a single heterogeneous nucleation event at the contact point, the nucleation density with the wheel surface heated to $200^{\circ}C$, was $4{\times}10^6/mm^2$, and in the cases of BN coating with thin and thick layers, $10^5/mm^2$ and $5{\times}10^4/mm^2$, respectively. The largest cooling capacity of the wheel corresponded to the heated wheel surface, and as the thickness of BN coating layer increased, the cooling capacity of the wheel gradually decreased.

Influence of Si contents on the mechanical properties and microstructure of austempered ductile iron was investigated. Four different Si contents between 2.0 and 2.9% were used. Austenitizing was performed at $890^{\circ}C$ for 2 hrs and austempering temperatures were both 340 and $380^{\circ}C$ for 0.5, 1, and 2 hrs. Nodule content was more than $300/mm^2$ and nodularity was more than 90%. Microstructure was revealed using nital and retained austenite was measured by x-ray diffractometer. Tensile test, no-notch Charpy impact test and wear test were performed. Tensile strength was improved as Si content increased and both elongation and impact toughness had peak at 2.6%Si. The specimen austempered at $380^{\circ}C$ showed lower tensile strength than that of $340^{\circ}C$, but showed higher elongation. However, austempering temperature of $380^{\circ}C$ was desirable because that of $340^{\circ}C$ was close to lower bainite transformation. As austempering time increased, tensile strength and elongation were improved and optimum condition was obtained for 2 hrs heat treatment.

In spite of the fact that magnesium has low density and good machinability, its applications are restricted as a structural engineering material because of the poor strength, ductility, and corrosion resistance of the conventional ingot metallurgy alloys. Such properties can be improved by microstructural refinement via rapid solidification processing. In this study, Mg-5wt%Zn alloys have been produced as continuous strips by the melt overflow technique. In order to evaluate the influence of the cooling rate on the grain refinement and mechanical properties, seven different thickness strips were produced by means of controlling the speed of the cooling wheel. Then the microstructual observations were undertaken with the objective of evaluating the grain refinement as function of the cooling rate. The tremendous increase in hardness of Mg-Zn alloy was mainly due to the refinement of the grain structure by the effect of rapid solidification. The formation of intermetallic phases on the grain boundaries may have a positive effect on the corroion resistance. Therefore, despite competition from many other developments, the rapid solidification process emerges as a valuable method to develop superior and commercially acceptable magnesium alloys.