九州大学 · 工学
Avala Lavakumar教授の研究室は、金属材料の微細構造と物理的・機械的性質の関係に焦点を当てた研究を推進しています。特に、マルテンサイト鋼やTRIP効果を示す多相鋼の変形挙動、高エントロピー合金を用いた新規バインダー材料の開発、および微小硬度試験におけるインデンテーションサイズ効果の解明が主な研究テーマです。実験的手法(X線回折、EBSD、TEMなど)と理論的解析を融合した、材料の微視的挙動を解明する研究が特徴です。
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The progress of civilization can be, in part, attributed to our ability to employ metallurgy. This book is an introduction to multiple facets of physical metallurgy, materials science, and engineering. As all metals are crystalline in structure, attention is focussed on these structures, and how the formation of these crystals is responsible for certain aspects of the material's chemical and physical behaviour. The book also discusses the mechanical properties of metals, the theory of alloys, an
Indentation Size Effect (ISE) in steels having a wide spectrum of carbon (C) concentrations (wt-%) 0.002 (interstitial-free), 0.07 (microalloyed), 0.19 (low carbon), 0.32 (medium carbon), and 0.7 (high carbon), and microstructures were investigated using Vickers micro-hardness tester. A decrease in micro-hardness with increasing load, i.e. ISE, is observed in all the samples except microalloyed steel. The empirical relations, such as the Nix and Gao model, Minimum Resistance model, and Proportio
The current review gives an insight into high-entropy alloys (HEAs) as a new possible binder material for the tungsten carbides, heavy tungsten alloys, and titanium carbo-nitride (Ti(C,N)) based cermet composites. The existing binder materials (for instance, Co, Ni, etc.), produced by powder metallurgy methods, have limited tool bits performance and short service life while mining applications; however, replacing existing binders with more accurate binder material is still a great challenge for
Abstract Multi-phase steels showing transformation induced plasticity (TRIP), can exhibit an excellent combination of high strength and good ductility by the aid of martensitic transformation during deformation. Even though TRIP-assisted multi-phase steels have been widely used in industry, the role of each phase in the enhancement of mechanical properties is still unclear given their complicated microstructures. In order to understand better the nature of the TRIP effect, the mechanical interac
In general, the stress-strain relationship of materials obtained by standard uniaxial tensile test, which can identify the hardening behavior only up to necking. Beyond necking, the material behavior is usually estimated by extrapolating or numerical modelling based on hardening behavior prior to the uniform elongation. This study investigated the post-necking hardening behavior of a fully martensitic steel by in-situ synchrotron X-ray diffraction during tensile deformation. From the in-situ res
TRIP-assisted multiphase steels are gradually finding employment in the automotive industry for their excellent strain-hardening characteristics. In the current study, in a comparatively lean composition steel, different combinations of multiple phases such as ferrite, austenite and martensite, were obtained by heat-treatment, consisting of Inter-critical annealing followed by partitioning treatment for different holding times. It was observed that, with increasing isothermal holding time, the v
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