Advanced Materials Research Vols. 415-417

Abstract: The discovery of the icosahedral quasicrystalline phase (i-phase) in as-cast Ti_40.83Zr_40.83-xSc_xNi_18.34 (x = 0~2.0) alloys is described herein. The effect of Sc on the structure and mechanical properties of the bulk quasicrystalline alloys is investigated. The results show that the phase structure of the as-cast alloys are mainly composed of icosahedral phase accompanied by minor C14 Laves phase (L-phase), and the mechanical properties of the bulk quasicrystalline alloys have been examined at room temperature, the compressive fracture strength first increased and then decreased with increasing x from 0.4 to 2.0, and the highest strength is near 1400 MPa when x =1.2, it was 380 MPa higher than the without Sc alloy. The bulk quasicrystalline alloy exhibits the elastic deformation by the compressive test, and the fracture mode was brittle cleavage fracture.

Abstract: Mechanical properties of extruded Mg-Zn-Nd-Y-Zr alloy are investigated by tensile tests at various temperatures range from room temperature to 350°C with strain rates of 6.0×10^-4-6.0×10^-1 s^-1. It is found that the peak decrease with increasing temperature and decreasing strain rate, while the elongation increases with increasing temperature and decreasing strain rate. When deformation temperature is over 250°C, superplasticity occurs. This is ascribed to grain boundary sliding accommodated cavities growth. . At low temperature, the peak stress are a relatively higher than that of ZK60 alloy. This is explained by the grain refining effect and the precipitates of Mg₉Nd and Mg₆Zn₃Y₂.

Abstract: Benzyl esters of fatty acids based on three types of vegetable oils (i.e., coconut, palm, and soybean oils) were in-house prepared. They were used as alternative rubber processing oil to replace conventional aromatic oil which has been banned by European community since December 2009. Fatty acids were first prepared by hydrolysis of vegetable oils and thereafter esterified with benzyl alcohol in the presence of sulfuric acid as a catalyst. The reaction based on molar ratio of fatty acid:benzyl alcohol:sulfuric acid was set at 1.5:1.0:0.05 gave yield of benzyl esters higher than 80%. Rubber compounds containing different types of benzyl ester were prepared according to the standard formulation of ASTM 3184. It was found that the processing oil in the form of benzyl esters is possible to use instead of aromatic oil in rubber formulation. Various parameters and properties include mixing energy, Mooney viscosity, curing, mechanical and dynamic mechanical properties of rubber compounds and vulcanizates have been investigated.

Abstract: The typical Landau free energy functional with the fourth power of a solute composition field is not suitable for representing spinodal decomposition of a dilute Ag solute field in Al-Ag alloy. Facing this challenge, a new free energy density function is proposed for spinodal decomposition of a dilute Ag solute field of Al-Ag alloy. The evolution of the solute field in Al-4.2% Ag alloy is studied by phase-field method using this new function. The simulated results reveal that the precipitate free zone (PFZ) around the precipitated phase is an ellipse and its width is about two times that of phase, while in the region far from PFZ, a GPZ pattern of Ag solute field appears due to spinodal decomposition.

Abstract: Copper tube produced by FA6502 copper alloy in a company of Wuhan appears shrinkage cavity in horizontal continuous casting, the graphite mold core which exerts stretching effects is easy to be snapped in production process. The reason why shrinkage cavity appears is found through large number of experiments and analysis. Then we adjust the component of FA6502 copper alloy, the quality of new copper alloy FA6506 is improved significantly. Furthermore, we find the reason why the graphite mold core is snapped in production process, FA6502 copper alloy’s shrinkage rate is too large in solidification. The compact power of the graphite mold core is too large to bear, too much resistance in pulling process is exerted so that the graphite mold core is snapped.

Abstract: This study sought to create a biocomposite of Magnesium and Titanium via a powder metallurgy technique. Powder metallurgy technique was used to produce three different volume percentages of Magnesium (30% , 35% , 40%). Titanium powder was mixed with Magnesium, then the samples were compressed by 1800 Bar using a cold, isostatic press process. The samples were then sintered to 850 for 100 min. At this temperature, the compressive yield strength was increased to 210 Mpa and significantly depended on the volume percent of Magnesium present, the core size and temperature of sintering. The bioactivity of the samples in a simulated body fluid (SBF) was also investigated. When the samples were immersed in the simulated body fluid for a 14 and 28 days, calcium and other elements were found to be deposited on the surface. Additionally, it was found that TiO2 has the ability to induce the formation of bone-like apatite in the SBF. In addition, the degradation product of Magnesium in a biological system caused a rise in the pH and environment for the deposition of calcium and other element on the surface were enhanced. Finally, the samples were analyzed using XRD, EDS, and optical and scanning electron microscopy (SEM).

Abstract: In electronic packaging industry, they are now driven technology to green product by replacing leaded-solder with lead-free solder in order to fulfill the European Restriction of Hazardous Substance (RoHS) compliance. Thus, Sn-Ag-Cu lead-free solder family is one of candidates can fulfill this requirement. This study investigates the interfacial reactions during reflow soldering and isothermal aging between Sn-3.0Ag-0.5Cu (SAC305) and electroless nickel/ immersion palladium/immersion gold (ENEPIG). Reliability of solder joint is also examined by performing solid state isothermal aging at 125°C and 150°C for up to 2000 hours. The results revealed that after reflow soldering, (Cu, Ni)₆Sn₅ IMC is formed between solder and substrate while after aging treatment another IMC was found between (Cu, Ni)₆Sn₅ and substrate known as (Ni, Cu)₃Sn₄. Aging time and temperature of solder joints results in an increase of IMC’s thickness and changes their morphologies to become more spherical, dense and with larger grain size. In addition, the results also revealed that the thickness of intermetallics formed is proportional to the aging duration and temperature.

Abstract: Low carbon steel is widely used in industries due to its low cost and easy to recycle. However, the low carbon steel is also known that easily attacked by environment and low strength compared with other kinds of steel. Therefore, several surface coating and treatment techniques are employed to improve its properties. This study was aimed to investigate influence of combined processes between gas soft nitriding and gas carburizing on the hardness of low carbon steel. The specimen was normalized by normalizing and shot blasting. Then the specimen was treated by gas carburizing, gas carbonitriding and combined processes between gas soft nitriding and gas carburizing. It was found that the combined processes yielded the good surface hardness and total case depth compared to other conditions. The most advantage of the combined processes could be considered to be very small variation of hardness.

Abstract: In order to find out the kiln of some articles unearthed at Fancui tomb of Northern Dynasty, we use the article samples to track to a kiln site near Cao village, Linzhang town, Hebei province. By compare and contrast of Cao village kiln samples with Northern Dynasty tomb articles, we conclude that Cao village kiln are of Northern Dynasty. We measure the physical properties and the chemical composition of the samples using energy dispersive X-ray fluorescence (EDXRF), and identify the samples are of lead glaze pottery, Fuzzy cluster analysis of the samples shows that Cao village kiln body samples raw materials come from 3~4 batches, while the glaze samples raw material come from 3 batches. It also shows that the body raw materials and the glaze raw materials of the sample supporting pins are the same as those of Cao Village kiln.

Abstract: Polyurethane dispersion modified with polymethylsiloxane (Si-PUD) and its nanocomposites incorporated with clays (Cloisite 15A and 30B at 3 and 6 wt%) were synthesized and characterized in this work. FTIR analysis showed that Si-PUD and Si-PUD/clay nanocomposites were successfully manufactured. While the glass transition temperature was not affected by the modification of the siloxane and clays, thermal resistance from TGA and mechanical properties such as tensile strength and elongation at break from UTM were largely enhanced at 3 wt% of both C15A and C30B clay. Higher content of 6 wt% of C30B has inferior to other Si-PUD samples containing clay in mechanical properties. Surface with higher hydrophobicity was observed for Si-PUD and Si-PUD/clay nanocomposites compared to PUD.