In-Hyung Moon

Bio: In-Hyung Moon is an academic researcher from Hanyang University. The author has contributed to research in topics: Sintering & Eutectic system. The author has an hindex of 10, co-authored 23 publications receiving 437 citations.

High temperature performance of dispersion-strengthened AlTi alloys prepared by mechanical alloying

Abstract: Dispersion-strengthened AlTi alloys were prepared by the mechanical alloying (MA) process and hot consolidation method, and their high temperature mechanical properties and oxidation properties were investigated. The tensile strengths of MA AlTi alloys were substantially higher than those of conventional Al alloys such as 7075 and 2024 grades at temperatures above 150°C. The compressive strength and the yield strength of MA Al8wt.%Ti at 350°C with a strain rate of 1 × 10 −4 s −1 were 233 MPa and 186 MPa respectively. The measured parabolic rate constant k p in oxidation of the MA Al8wt.%Ti alloy at 600°C was a much lower value, approximately 1.12 × 10 −13 g 2 cm −4 s −1 , which revealed that the oxidation resistance of the MA alloy was much better than that of the 2024-TB Al alloy.

The effect of manganese addition on the microstructure of W-Ni-Fe heavy alloy

Abstract: The influence of Mn addition on the growth kinetics and morphology of W grains in W-Ni-Fe heavy alloy has been studied. The addition of Mn was performed by placing a compact of Mn powder on the sintered specimens containing constant Ni/Fe ratio of 8/2 but different W contents of 93 and 97 wt pct followed by resintering. The sintering and resintering treatments were carried out at a temperature of 1485 °C under a dry hydrogen atmosphere. The addition of Mn leads to the deviation of growth rate of W grains from the diffusion-controlled Ostwald ripening: the growth rate is initially enhanced and then decayed. The difference in the average grain radius between the alloys containing high and low W contents is decreased by the addition of Mn. The cause of the change in the growth rate of W particles with the addition of Mn is discussed in terms of the competitive soluble reactions of Mn and W atoms. The addition of Mn also results in the morphological change of W grains from roudish to angular shape. The addition of Mn into the matrix phase, which is artificially made, forms the dendritic W grains. From these results, it is found that the morphological change of W grains is closely related to the precipitation reaction of W atoms on the preferred orientation.

Consolidation/synthesis of materials by electric current activated/assisted sintering

Abstract: This review article aims to provide an updated and comprehensive description of the development of the Electric Current Activated/assisted Sintering technique (ECAS) for the obtainment of dense materials including nanostructured ones. The use of ECAS for pure sintering purposes, when starting from already synthesized powders promoters, and to obtain the desired material by simultaneously performing synthesis and consolidation in one-step is reviewed. Specifically, more than a thousand papers published on this subject during the past decades are taken into account. The experimental procedures, formation mechanisms, characteristics, and functionality of a wide spectrum of dense materials fabricated by ECAS are presented. The influence of the most important operating parameters (i.e. current intensity, temperature, processing time, etc.) on product characteristics and process dynamics is reviewed for a large family of materials including ceramics, intermetallics, metal–ceramic and ceramic–ceramic composites. In this review, systems where synthesis and densification stages occur simultaneously, i.e. a fully dense product is formed immediately after reaction completion, as well as those ones for which a satisfactory densification degree is reached only by maintaining the application of the electric current once the full reaction conversion is obtained, are identified. In addition, emphasis is given to the obtainment of nanostructured dense materials due to their rapid progress and wide applications. Specifically, the effect of mechanical activation by ball milling of starting powders on ECAS process dynamics and product characteristics (i.e. density and microstructure) is analysed. The emerging theme from the large majority of the reviewed investigations is the comparison of ECAS over conventional methods including pressureless sintering, hot pressing, and others. Theoretical analysis pertaining to such technique is also proposed following the last results obtained on this topic.

Hallmarks of mechanochemistry: From nanoparticles to technology

Abstract: The aim of this review article on recent developments of mechanochemistry (nowadays established as a part of chemistry) is to provide a comprehensive overview of advances achieved in the field of atomistic processes, phase transformations, simple and multicomponent nanosystems and peculiarities of mechanochemical reactions. Industrial aspects with successful penetration into fields like materials engineering, heterogeneous catalysis and extractive metallurgy are also reviewed. The hallmarks of mechanochemistry include influencing reactivity of solids by the presence of solid-state defects, interphases and relaxation phenomena, enabling processes to take place under non-equilibrium conditions, creating a well-crystallized core of nanoparticles with disordered near-surface shell regions and performing simple dry time-convenient one-step syntheses. Underlying these hallmarks are technological consequences like preparing new nanomaterials with the desired properties or producing these materials in a reproducible way with high yield and under simple and easy operating conditions. The last but not least hallmark is enabling work under environmentally friendly and essentially waste-free conditions (822 references).

Nanocrystalline materials and coatings

Abstract: In recent years, near-nano (submicron) and nanostructured materials have attracted increasingly more attention from the materials community. Nanocrystalline materials are characterized by a microstructural length or grain size of up to about 100 nm. Materials having grain size of ∼0.1 to 0.3 μm are classified as submicron materials. Nanocrystalline materials exhibit various shapes or forms, and possess unique chemical, physical or mechanical properties. When the grain size is below a critical value (∼10–20 nm), more than 50 vol.% of atoms is associated with grain boundaries or interfacial boundaries. In this respect, dislocation pile-ups cannot form, and the Hall–Petch relationship for conventional coarse-grained materials is no longer valid. Therefore, grain boundaries play a major role in the deformation of nanocrystalline materials. Nanocrystalline materials exhibit creep and super plasticity at lower temperatures than conventional micro-grained counterparts. Similarly, plastic deformation of nanocrystalline coatings is considered to be associated with grain boundary sliding assisted by grain boundary diffusion or rotation. In this review paper, current developments in fabrication, microstructure, physical and mechanical properties of nanocrystalline materials and coatings will be addressed. Particular attention is paid to the properties of transition metal nitride nanocrystalline films formed by ion beam assisted deposition process.

Challenges and advances in nanocomposite processing techniques

Abstract: Of late, nanotechnology seems to be rapidly thrusting its applications in all aspects of life including engineering and medicine. Materials science and engineering has experienced a tremendous growth in the field of nanocomposite development with enhanced chemical, mechanical, and physical properties. A wide array of research has been conducted in the processing of nanocomposites. Consolidation of these systems from loose particles to bulk free form entities has always been a challenge. To name a few, traditional consolidation techniques such as cold pressing and sintering at high temperatures, hot pressing, and hot isostatic pressing have strong limitations of not being able to retain the nanoscale grain size due to the excessive grain growth during processing. This article reviews in detail the results from numerous studies on various methods for manufacturing nanocomposites with improved properties and retained nanostructures. Both challenges and recent advances are discussed in detail in this review.

The Limits of Refinement by Severe Plastic Deformation

Abstract: The effect of the different processing parameters on the refinement during severe plastic deformation is evaluated. The attention is focused to very high strains, where saturation in the structural refinement is observed. The single phase metals and alloys show a relatively uniform behaviour, with increasing strain the size of structural elements decreases and reaches saturation between equivalent strains of 5 to 50. The resulting ultra fine or nanostructured granular microstructure contains mainly high angle grain boundaries. Alloying, the temperature, and the strain path are the most important parameters controlling the saturation in the structural refinement. The behavior of the dual and multiphase materials during SPD is more complex, it varies from simple homogenisation of the phase distribution, fragmentation of one phase to disintegration and supersaturation of the phases. Severe plastic deformation of these types of materials offers the potential for the production of new types of materials with a nanocrystalline or a nanocomposite structure for a broad range of industrial applications.