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A complex multi-layer AA1050/AA5052 aluminum alloy was fabricated by an accumulative roll-bonding (ARB) process. A two-layer stack ARB was performed up to three cycles at ambient temperature without a lubricant according to the conventional procedure. A sound complex multi-layer AA1050/AA5052 aluminum alloy sheet was successfully fabricated by the ARB process. For further enhancement of the mechanical properties, the ARB-processed complex aluminum alloy sheets were further rolled to about 50% reduction by conventional rolling with the same rolling machine, which resulted in a thickness of just 1 mm. The mechanical properties of the ARBprocessed materials were investigated in detail and compared to the results of previous studies.

keyword : accumulative roll-bonding, mechanical property, AA1050/AA5052 complex aluminum alloy, rolling conditions

The optimum conditions for FOTS films deposited as vapor self-assembled monolayers for producing a hydrophobic film with low roughness was determined to be 10 Torr and 50℃. The root mean square (RMS) of film roughness was 0.72 nm and its contact angle 108.14°. These conditions are much simpler than the conventional process in which high temperature is known to result in high contact angles and reduced agglomeration of precursor molecules and roughness. However, we found that optimized hydrophobic FOTS film that provides an anti-stiction layer in micro-electro-mechanical systems can be obtained at low temperature and high pressure with a comparable contact angle to and lower roughness than the film obtained using the conventional process.

keyword : thin films, vapor deposition, surface, atomic force microscopy, self assembled monolayer

It is well-known that foot-and-mouth disease (FMD) disinfectant was sprayed on every road near the areas infected by FMD in order to prevent the spread of the disease. Environmental, harmful, and corrosive effects from the spraying of FDM disinfectant are current issues. Most of FMD disinfectant was acidic and many people are concerned about the corrosion of metallic parts of cars, houses and other structures. This work evaluated the effect of FMD disinfectant on the corrosion of carbon steel, aluminium, and galvanized steel. Regardless of the FMD disinfectant, the pHs were acidic and the reduction-oxidation potentials were highly noble. The results of a polarization test confirmed that carbon steel and galvanized steel exhibited anodic dissolution by anodic polarization, but only aluminium exhibited passivity. In an immersion test, the corrosion rate of aluminium was the lowest among three alloys, and with a decreasing dilution ratio of the disinfectants, the corrosion rate of the three alloys linearly increased. Furthermore, an empirical equation to estimate a corrosion rate by various dilution ratios was derived.

keyword : metals, corrosion, foot-and-mouth disease, disinfectant, corrosion, carbon steel, galvanized steel, aluminum

This study investigated the effect of heat input in overlay welding using stainless steel FCW on the dilution ratio and characteristics of microstructural evolution, initiation and propagation of a bending crack in the overlay weldment. When the heat input was varied in the range of 3.2-19.8 kJ/cm by adjusting welding parameters such as current, voltage and speed, the dilution ratio was the highest in 7.9- 9.9 kJ/cm with the lowest values of Creq and Nieq, for which the formation of martensite was predicted by the Schaeffler diagram, and its existence was confirmed by optical microscopy. In addition, the width of the transition zone was the largest in heat input of 7.9-9.9 kJ/ cm, and martensite was observed in the transition zone of the first weld layer of E309LT1-1 (welding material) and ASTM A516 Gr.70 (base metal). According to the bending test, cracks were observed in the specimens with heat input of 8.6-9.5 kJ/cm.

keyword : metals, welding, microstructure, scanning electron microscopy, heat input

MgH2, rather than Mg, was employed as a starting material in this work. A sample with a composition of 82 wt% MgH2-18 wt% Ni (designated MgH2-18Ni) was prepared by reactive mechanical grinding. Its hydriding and dehydriding properties were then examined. An MgH2-Ni hydrogen-storage alloy that does not require an activation process was developed. The alloy was prepared by grinding for 4 h in a planetary ball mill at a ball disc revolution speed of 250 rpm under a hydrogen pressure of about 12 bar. The sample absorbed 3.51 wt% H for 5 min and 3.96 wt% H for 60 min at 573 K under 12 bar H2, and desorbed 0.90 wt% H for 10 min and 3.24 wt% H for 60 min at 573 K under 1.0 bar H2. MgH2-18Ni after reactive mechanical grinding contained β-MgH2, Ni, γ-MgH2 (a high-pressure form of MgH2), and a very small amount of MgO. The specific surface area and average particle size of MgH2-18Ni after reactive mechanical grinding were analyzed.

keyword : hydrogen absorbing materials, mechanical alloying/milling; microstructure, X-ray diffraction, MgH2-18 wt% Ni

This study investigated the effects of intermediate annealing temperature and final reduction ratio on the recrystallization structure of a twin-roll continuous cast and cold rolled Al alloy after brazing heat treatment. The grain structure after brazing heat treatment of the intermediate-annealed specimen at a lower temperature of 410℃ was coarser than that at a higher temperature of 470℃. The dispersoids of nanometer size particles, which had been absent in the as-cast specimen, were precipitated during the intermediate annealing and significantly influenced the recrystallized grain structure during brazing heat treatment. Even though the grain size of the specimen rolled with a lower final reduction ratio of 30% was a little finer than that with a higher one of 40% after the intermediate annealing, the former was much coarser than the latter after the brazing heat treatment.

keyword : alloys, annealing, recrystallization, transmission electron microscopy, cold working

From polarization-electric field (P-E) results of the (1-x)Pb(Yb1/2Nb1/2)O3-xPbTiO3 ((1-x)PYN-xPT, 0.30≤x≤ 0.70) solid solutions tested at room temperature, remanent polarization (Pr) and coercive field (Ec) values with composition ranges of 0.30 ≤x ≤0.40 tended to increase gradually. In the composition of 0.46 ≤x ≤0.56 including the morphotropic phase boundary (MPB), the Pr values decreased as a whole, but the Ec values increased. For the temperature effect, the area of hysteresis loops in the composition of 0.44 ≤x ≤0.50 decreased from room temperature to 220℃, which shows the typical characteristics found in ferroelectrics. Piezoelectric measurements revealed a maximum piezoelectric constant (d33) of 302 pC / N at x = 0.50.

keyword : ceramics, powder processing, electrical properties, electrical, morphotropic phase boundary

Previously, Gum Metal (Ti-24(Nb + Ta + V)-(Zr, Hf)-O (at%)) exhibiting an ultralow Young`s modulus, ultrahigh strength and super elasticity was developed by Saito et al., who proposed that three electronic magic numbers, an average electron/atom (e/a) ratio of 4.24, an average bond order (Bo) of about 2.87, and an average “d” electron-orbital energy level (Md) of about 2.45 eV, should be satisfied simultaneously to obtain such “super” properties. The purpose of this study was to find new alloy systems possessing those properties and to examine the effect of beta equivalent content ([Mo]eq) on Young`s moduli of new alloys having the same three electronic numbers mentioned above. It was found that not only three electronic numbers but also [Mo]eq should be considered to obtain a similar Young`s modulus and hardness with respect to the Gum Metal.

keyword : alloys, cold working, mechanical properties, ultrasonics, DV-Xａ method

We conducted melt-down experiments on Al-xMg-carbon nanotube (CNT) complex powder compacts at 700℃ and 800℃ for carrying the CNTs into the molten Al7021 matrix alloy. The parameters in the melting experiments were the holding temperatures and the amount of Mg content. The microstructures of the melt-down compacts were observed by optical microscopy (OM) and field emission scanning electro-microscopy (FESEM). The several phases obtained from the reaction products within the Al-xMg-CNT compacts were identified by energy dispersive X-ray spectroscopy (EDXS) and X-Ray diffractometry (XRD). The complete melt-down area was increased due to a large addition of Mg in the compacts and outer areas remained as undissolved powder compacts due to the large number of oxidation products such as MgO, MgAl2O4 and Al2O3. CNTs were observed on the surface of Al powders with oxidation products at 700℃ in a melting experiment. However, at 800℃, the CNT agglomerates moved away from the center because of the poor wettability and low density of the CNTs.

keyword : composites, sintering, oxidation, X-ray diffraction, carbon nanotube