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Brazing characteristics of a Zr(Ti)–Cu(Fe)–Al glassy alloy was investigated using a Zircaloy-4 alloy as a base metal. A low melting temperature (solidus: 840 °C, liquidus: 880 °C) of the brazing alloy was obtained at the near-eutectic composition of Zr 55 Ti 5 Cu 25 Fe 5 Al 10 (at.%) designed by a partial replacement of Zr by Ti, and Cu by Fe from a well-known Zr 60 Cu 30 Al 10 ternary alloy. This quinary brazing alloy exhibited excellent melting and wetting characteristics and good compatibility with the base metal. At brazing temperatures below the liquidus of the brazing alloy, the joint consisted of a relatively fine dendritic structure ( α -Zr + Zr 2 Cu) with a massive segregation of Zr 2 Cu in the central zone by a eutectic solidification of the molten brazing alloy during a cooling stage, whereas a homogeneous joint was obtained at 890 °C with a predominant formation of acicular α -Zr phases holding an intercellular lamellar mixture ( α -Zr + Zr 2 Cu), which was produced by an isothermal solidification during a brazing holding time. The mechanical properties of the joints were strongly dependent on a degree of joint homogeneity, and the bonding strength of the joints was high enough to cause a fracture in the Zircaloy-4 base metal, when the central segregation of massive Zr 2 Cu was completely eliminated at the brazing temperature of 890 °C.

A Zr–Ti–Cu–Fe quaternary eutectic alloy was employed as a new Be-free brazing filler metal for Zircaloy-4 to supersede physically vapor-deposited Be coatings used conventionally with several disadvantages. The quaternary eutectic composition of Zr 58 Ti 16 Cu 10 Fe 16 (at.%) showing a low melting temperature range from 832 °C to 853 °C was designed by a partial substitution of Zr with Ti based on a Zr–Cu–Fe ternary eutectic system. By applying an alloy ribbon with the determined composition, a highly reliable joint was obtained with a homogeneous formation of predominantly grown α -Zr phases owing to a complete isothermal solidification, exhibiting strength higher than that of Zircaloy-4. The homogenization of the joint was rate-controlled by the diffusion of the filler elements (Ti, Cu, and Fe) into the Zircaloy-4 base metal, and the detrimental segregation of the Zr 2 Fe phase in the central zone was completely eliminated by an isothermal holding at a brazing temperature of 920 °C for 10 min.

Magnetic pulsed compaction (MPC) was introduced to consolidate conventional iron-based powders for the production of high-density steel parts in powder metallurgical (PM) processing. Highly dense steel components of Fe–1.5Cr–0.2Mo–0.25 C (wt.%) were obtained with green and sintered densities of 7.63 g/cm 3 and 7.75 g/cm 3 (full density: 7.8 g/cm 3 ). This anomalous densification in the MPC process was attributed to the complementary kinetic effect by the high impact pressure in a very short duration, allowing the enhanced particle rearrangement and plastic deformation in the compacted powders. Owing to this superior compactability, the intact compacts were fabricated efficiently even with the small addition of lubricant (less than 0.05 wt.%). Also, die wall lubrication was effective for preventing surface damage as well as for promoting homogeneous densification during the MPC. These results show a potential for application of the MPC process to high-density steel PM parts.

Microstructural evolution of the Ti–Cu dissimilar joints brazed by a Zr 41.2 Ti 13.8 Cu 12.5 Ni 10.0 Be 22.5 (at.%) amorphous alloy filler was investigated at a temperature of 820 °C for 1–20 min. As the brazing time increased, the overall composition of the joint sensitively changed from Ti-rich to Cu-rich owing to the different reactivity of the Zr in the filler with the Ti and Cu in the base metals. Based on such time-dependent compositional change, the formation of the intermetallic phases in the joint was basically divided into three stages; Stage (1): formation of interfacial Ti 2 Cu, Stage (2): formation of two-phase structure with Ti 2 Cu/TuCu and Cu 2 TiZr, and Stage (3): transformation to Cu-rich phases. At Stage (2), the joint was fully produced isothermally by directional phase transformations with fine dendritic and columnar two-phase structures, revealing the highest bonding strength due to its controlled intermetallic morphology.

Titanium (Ti) was successfully brazed at low temperatures below 800 °C by employing a Zr41.2Ti13.8Ni10.0Cu12.5Be22.5 (at.%) bulk metallic glass (BMG) alloy as a filler. Through the use of this alloy filler, the detrimental segregation of Zr–Cu–Ni filler elements was completely eliminated by heating to well below 800 °C, so the resultant joint was quite homogeneous with a coarse acicular structure. The disappearance of the Zr–Cu–Ni segregated region was rate-controlled by the diffusion of the filler elements in the Ti base metal. Remarkably, the mechanical property and corrosion resistance of the homogeneous joint brazed at 800 °C for 10 min were mostly comparable to those of bulk Ti.

Strong bonding between titanium (Ti) and stainless steel (STS) was achieved by employing a commercially available Ag–28Cu (wt.%) filler, and more importantly with a help of an Ag interlayer. A mass transport of the Ti elements from the substrate into the molten filler was completely prevented through the use of the Ag interlayer, so the resultant brazed joint was free from any brittle Ti-based intermetallic compounds. Notably, this Ti–STS dissimilar joint displayed a remarkable improvement in its bonding strength, demonstrating the potential application of an Ag interlayer for joining Ti and its alloys to various structural steels.

In this study, the effects of precompaction on the density, microstructure, mechanical and electrical properties of α-Al 2 O 3 bulks fabricated by the combined application of magnetic pulsed compaction (MPC) and a sintering process were reported. The obtained density of the α-Al 2 O 3 bulks prepared by the combined processes increased with the increasing MPC pressure and precompaction pressure. The resultant higher hardness and breakdown voltage of the consolidated bulks following combined application of the magnetic pulsed compaction, precompaction and sintering process could be attributed to the homogeneously distributed ultra-fine microstructure than that of general processing, suggesting that the grain growth was remarkably reduced during the MPC processes.

The microstructure and mechanical properties of Ti joints brazed with a Zr41.2Ti13.8Ni10.0Cu12.5Be22.5 (at.%) amorphous filler were investigated. With a Zr-based amorphous filler, in this study, Ti joints with a homogeneous composition could be obtained by heating to well below the α-β transformation temperature for a short time, so that the undesirable effects of the high temperature heating are considerably diminished. The joints brazed at 790 °C for 10 min consisted of the coarse acicular structure rather than the fine Widmanstätten structure which generally deteriorates the ductility of the joints. The joints with the homogenous coarse acicular structure, i.e. without a residual liquid region, show almost the same mechanical properties as those required for base metals without heating. Although the residual liquid region in the joints deteriorates the ductility of the joints, this region could be successfully removed by a diminution in the quantity of the filler.

In this study, joining characteristics of dissimilar Ti and Cu metals have been investigated, when using both an Ag-based eutectic alloy as a filler and an Ag layer present on Ti base metal as a diffusion barrier. The observed microstructures were classified into three characteristic types, depending on the presence of a Ag layer at the Ti interface, e.g. first, the sample retaining thick continuous intermetallic layers, e.g. Ti2Cu, TiCu, Ti3Cu4, Ti2Cu3, and TiCu4 by a significant dissolution of the Ti atoms into the molten filler, in the absence of a Ag coating layer onto the Ti base metal, second, the sample with relatively thin Ti-Cu intermetallic layers by the reduced reaction of Ti with Cu due to a prominent decrease in the Ti dissolution, owing to the role of the Ag coating layer as a diffusion barrier, and finally, the sample without any brittle Ti-Cu intermetallics in the joint by a complete suppression of both the dissolution of the Ti atoms and its reaction with the Cu elements in the molten filler due to the presence of a Ag layer.

The fracture property improvement of Zr-based bulk amorphous alloy containing ductile crystalline particles was explained by directly observing microfracture processes using an in situ loading stage installed inside a scanning electron microscope (SEM) chamber. Strength and apparent fracture toughness measured from the in situ fracture test of the amorphous alloy containing crystalline particles were lower than those of the monolithic amorphous alloy, whereas its ductility was higher. According to the microfracture observation, shear bands were initiated from ductile crystalline particles, and the propagation of the shear bands or cracks was blocked by crystalline particles, thereby resulting in stable crack growth which could be confirmed by the fracture resistance curve (R-curve) behavior. This increase in fracture resistance with increasing crack length improved fracture properties of the alloy containing crystalline particles, and could be explained by mechanisms of blocking of crack or shear band propagation, formation of multiple shear bands, crack blunting, and shear band branching.

Microfracture mechanisms of Zr-based bulk metallic glass (BMG) alloy containing ductile crystalline particles were investigated by directly observing microfracture processes using an in situ loading stage. Strength of the BMG alloy containing crystalline particles was lower than that of the monolithic BMG alloy, while ductility was higher. According to the direct microfracture observation, crystalline particles initiated shear bands, acted as blocking sites of shear band or crack propagation, and provided the stable crack growth which could be confirmed by the R-curve analysis, although they negatively affected apparent fracture toughness. This increase in fracture resistance with increasing crack length improved overall fracture properties of the alloy containing crystalline particles, and could be explained by mechanisms of blocking of crack or shear band propagation, formation of multiple shear bands, crack blunting, and shear band branching.

Development of wrought Mg alloys, particularly in sheet form, is essential to support the growing interest for lightweight components in the automotive industry. However, development of Mg alloy sheets has been quite slow due to the complexity of sheet production originated from limited deformability of Mg. In this respect, twin-roll strip casting, a one-step processing of flat rolled products, can be an alternative for the production of Mg alloy sheets. In this study, AZ31 and experimental ZM series alloys are twin-roll strip cast into 2 mm thick sheets. The microstructure of the as-cast AZ31 alloy sheet consists of columnar zones near the roll side and equiaxed zones in the mid-thickness region. On the other hand, as-cast ZM series alloy sheets show equiaxed dendritic structure through the thickness of sheet. These alloys were subjected to various thermo-mechanical treatments and their tensile properties were evaluated. Twin-roll strip cast AZ31 alloy in H24 condition has equivalent yield and tensile strengths with similar ductility compared to commercial ingot cast AZ31-H24 alloy, indicating that twin-roll strip casting is a viable process for the fabrication of Mg alloy sheets. The experimental ZM series alloys have a large volume fraction of fine dispersoid particles in the microstructure, resulting from the beneficial effect of twin-roll strip casting on microstructural refinement. It has been shown that the experimental ZM series alloys have superior tensile properties compared to commercial ingot cast AZ31-H24 alloy, suggesting the possibility of the development of new wrought Mg alloy sheets by twin-roll strip casting.

In this study, three Fe-base amorphous alloys with quite different critical cooling rates were subjected to twin-roll strip casting to see the possibility of fabricating amorphous sheet by the same process. Continuous cooling transformation (CCT) diagrams of the alloys were calculated using the heterogeneous nucleation theory coupled with thermal data obtained during cooling to evaluate their critical cooling rates and glass forming abilities (GFAs). It shows that the GFAs calculated by CCT diagram are in agreement with the experimental results, while the well known empirical thermal parameters do not agree with the experimental results. Optimum twin-roll strip casting conditions have been determined based on the calculated critical cooling rates and the simulated thermal behavior of the sheet during twin-roll strip casting.

Twin-roll strip casting was utilized to fabricate the sheet products of Zr- and Cu-base bulk amorphous alloys with quite different glass forming abilities (GFAs). Simulation of the solidification behavior of the these amorphous forming alloys during twin-roll strip casting shows that suitable cooling rate can be achieved by twin-roll strip casting to form amorphous structure through the thickness of sheet. Optimum twin-roll strip casting conditions have been suggested based on the simulation results. Actual twin-roll strip casting shows that both Zr-base alloy with high GFA and Cu-base alloy with much less GFA can be strip cast forming amorphous structure. The results indicate that the twin-roll strip casting is a viable process for continuous fabrication of sheets of bulk amorphous alloys with a wide range of critical cooling rates.

Twin-roll strip casting has been utilized to fabricate the sheet products of bulk amorphous alloys. Simulation of solidification behavior and actual twin-roll strip casting show that the optimum casting conditions are such that the alloy is in supercooled liquid state at roll nip area rather than fully amorphized.

In this study, Zr-Ti-Cu-Ni-Be bulk metallic glass (BMG) alloys containing a small amount of crystalline phase particles were fabricated by strip casting, and their improvement of mechanical properties and fracture toughness was explained by direct observation of the microfracture process. The compressive and fracture toughness test results indicated that strength, strain to failure, and fracture toughness of the strip-cast BMG alloy containing coarse crystalline particles were higher than those of the as-cast monolithic BMG alloy or the strip-cast BMG alloy containing fine crystalline particles. From in-situ microfracture observations, the improvement of overall mechanical properties of the strip-cast BMG alloy containing coarse crystalline particles could be interpreted by taking consideration of both the existence of coarse crystalline particles and the role of the particles to block crack propagation and to form multiple shear bands. Such property improvement suggests new applicability of the strip-cast BMG alloys containing coarse crystalline particles, which can work as toughening and strengthening reinforcements, to structures and components requiring excellent mechanical properties.

Effects of crystalline particles formed in the strip cast Zr-base bulk metallic glass (BMG) alloy on ductility and strength were investigated in this study by directly observing microfracture processes. The compressive and fracture toughness test results indicated that ductility, strength, and fracture toughness of the strip cast BMG alloy were higher than those of the die cast monolithic BMG alloy, although the strip cast alloy contained a considerable amount (4.5 vol.%) of hard, brittle crystalline particles. The improvement of mechanical properties in the strip cast BMG alloy could be plausibly explained by mechanisms of (1) blocking of shear bands or crack propagation, (2) formation of multiple shear bands, and (3) crack deflection by crystalline particles.

Development of wrought Mg alloy, particularly in sheet form, are essential to support the growing interest for lightweight components in the automotive industry. However, development of Mg alloy sheets has been quite slow due to the complexity of sheet production originated from limited deformability of Mg. In this respect, strip casting, a one-step processing of flat rolled products, can be an alternative for the production of Mg alloy sheets. In this study, AZ31 and experimental alloys are strip cast into 2 mm thick strips. The microstructure of the as-cast AZ31 alloy strip consists of columnar zones near the roll side and equiaxed zones in the mid-thickness region. On the other hand, as-cast MX1 alloy strip shows equiaxed dendritic structure through the thickness of strip. The cooling rate estimated from the secondary dendrite arm spacing is around 102 K/s. These alloys were subjected to various thermomechanical treatments and their tensile properties were evaluated. Strip cast AZ31 alloy in H24 condition has equivalent yield and tensile strengths with similar ductility compared to commercial ingot cast AZ31-H24 alloy, indicating that strip casting is a viable process for the fabrication of Mg alloy strips. The experimental MX alloys have a large volume fraction of fine dispersoid particles in the microstructure, resulting from the beneficial effect of strip casting on microstructural refinement. It has been shown that the experimental MX0 alloy has superior tensile properties compared to commercial ingot cast AZ31-H24 alloy, suggesting the possibility of the development of new wrought Mg alloy sheets by strip casting.

Summary form only given. Atmospheric plasma has an advantage not to use vacuum equipments. Thus, many researchers are beginning to develop methods of plasma generation at the atmospheric pressure and to find various industrial applications of the atmospheric plasmas, which may replace vacuum plasmas. Photo-resist (PR) ashing process has been conducted in vacuum plasma. PR ashing has been conventionally done in wet ashing and dry ashing. But the wet ashing have many problems including high-cost, environmental pollution and so on. Therefore, the dry ashing is more preferable process. Unfortunately, the present dry ashing requires the vacuum equipments at the moment. This paper presents experimental results of the PR ashing using glow plasma at the atmospheric pressure. The plasma generation is powered by a RF power source. The PR ashing by the atmospheric pressure plasma was investigated under various processing conditions. The ashing rate has been investigated in terms of processing temperature, gas composition, gas flow rate, RF power and exposure time. We measured PR thickness using micro-area gauge (NanoSpec/AFT). The results of this study will be useful for the optimization of ashing process conditions at the atmospheric pressure.