Showing papers on "Quenching published in 2018"
TL;DR: In this article, the optical properties of X3Sc2Ga3O12 (X = Lu, Y, Gd, La) garnets doped with Cr3+ showing efficient 4T2 → 4A2 broad band NIR emission between 600 and 1000
160 citations
TL;DR: In this paper, a microstructurally-based method was proposed to design a proper quenching temperature to obtain an optimum microstructure comprising fine martensite laths and alternatively distributed thin austenite films, which has the optimum balance between fraction and stability of retained Austenite.
88 citations
TL;DR: In this article, the effect of pre-aging treatment on the bake-hardening response of an Al-Zn-Mg-Cu alloy was investigated, and it was determined that preaging immediately after quenching is an effective method to form stabilized Guinier-Preston zones, which can act as precursors to form the metastable η′ phase, and then improve the bake hardening response.
85 citations
TL;DR: In this article, the second nearest neighbor modified embedded atom method (MEAM) potentials were used to simulate the spontaneous homogeneous nucleation from aluminum (Al) melt, and the crystal structure of nuclei, critical nucleus size, critical temperature, induction time and nucleation rate were determined.
Abstract: Homogeneous nucleation from aluminum (Al) melt was investigated by million-atom molecular dynamics (MD) simulations utilizing the second nearest neighbor modified embedded atom method (MEAM) potentials. The natural spontaneous homogenous nucleation from the Al melt was produced without any influence of pressure, free surface effects and impurities. Initially isothermal crystal nucleation from undercooled melt was studied at different constant temperatures, and later superheated Al melt was quenched with different cooling rates. The crystal structure of nuclei, critical nucleus size, critical temperature for homogenous nucleation, induction time, and nucleation rate were determined. The quenching simulations clearly revealed three temperature regimes: sub-critical nucleation, super-critical nucleation, and solid-state grain growth regimes. The main crystalline phase was identified as face-centered cubic (fcc), but a hexagonal close-packed (hcp) and an amorphous solid phase were also detected. The hcp phase was created due to the formation of stacking faults during solidification of Al melt. By slowing down the cooling rate, the volume fraction of hcp and amorphous phases decreased. After the box was completely solid, grain growth was simulated and the grain growth exponent was determined for different annealing temperatures.
73 citations
TL;DR: In this paper, the microstructure and mechanical properties of the H11 hot-work tool steel and a leaner version of the same alloy (L-H11) processed by Selective Laser Melting were assessed as a function of specific microstructural conditions obtained by performing different heat treatments.
70 citations
TL;DR: In this article, the role of Zirconium in β-Ti alloys is clarified using X-ray diffraction, transmission electron microscopy, and atom-probe tomography.
69 citations
TL;DR: In this paper, the microstructure evolution of the nickel-aluminum bronze alloy was studied by heat treatment, including annealing, normalizing, quenching and aging, which can eliminate selective phase corrosion effectively.
63 citations
TL;DR: In this article, a nickel-aluminum bronze alloy component is built using wire-arc additive manufacturing process and optical and scanning electron microscopy morphologies, X-ray diffraction and mechanical tests in longitudinal, transverse and normal directions.
Abstract: In this paper, a nickel-aluminum bronze alloy component is built using wire-arc additive manufacturing process. In order to investigate the influence of anisotropy introduced by the wire-arc additive manufacturing process, the layer-by-layer manufactured components with different post-production heat treatments are characterized by optical and scanning electron microscopy morphologies, X-ray diffraction and mechanical tests in longitudinal, transverse and normal directions. The experimental results show that the deposit exhibits higher strengths in the longitudinal and transverse direction than in the normal direction. Also, the ductility of the alloy is significantly improved with the designed quenching and tempering method, and competitive mechanical properties are achieved when tempering temperature reaches 650 °C. In addition, the anisotropy in the additively manufactured alloy can be effectively modified by the quenching and tempering heat treatments.
59 citations
05 Jan 2018-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this paper, the authors show that retained austenite undergoes significant internal stresses generated during the thermal cycle and that these eigenstrains are attributed to the difference in Coefficients of Thermal Expansion (CTE) between martensite and Austenite and are predicted successfully with a purely elastic mean field approach.
Abstract: Quenching and Partitioning (Q&P) process permits to produce innovative microstructures containing large fraction of carbon enriched retained austenite. The present study highlights that austenite undergoes significant internal stresses generated during such thermal cycle. Both mechanical and chemical contributions are likely to affect its stability at room temperature and thus the resulting mechanical properties of the steel. The experiments carried out by High Energy X-Ray Diffraction (HEXRD) show unambiguously that internal stresses in austenite originate from martensitic transformation strain and from additional hydrostatic stresses induced during both reheating to partitioning temperature and final cooling. These eigenstrains are attributed to the difference in Coefficients of Thermal Expansion (CTE) between martensite and austenite and are predicted successfully with a purely elastic mean field approach. In the present study, retained austenite is shown to be in compression at room temperature. As a consequence, this state of stress contributes to stabilize retained austenite against a possible strain induced transformation at room temperature and affects the way to determine the carbon content in austenite.
52 citations
TL;DR: In this article, a review of the history, research and development in cryogenic treatment along with its applications is presented. And the improved mechanical properties are imputed to the low temperature conditioning of martensite in ferrous metal such as tool steel and second phase precipitation in non ferrous metals such as aluminum and magnesium alloys.
51 citations
TL;DR: In this article, the authors focused on the characterization of wall heat fluxes and its influence upon CO formation/oxidation within atmospheric flames in a side-wall quenching geometry.
TL;DR: In this article, the authors investigated steam corrosion of bulk ZrSi 2, pure Si, and zirconium-silicide coatings as well as water quenching behavior of ZRSi 2 coatings to evaluate its feasibility as a potential accident-tolerant fuel cladding coating material in light water nuclear reactor.
TL;DR: In this article, a series of Eu 3+ ions activated double perovskite CaLaMgSbO 6 phosphors were successfully synthesized and the crystal structure was investigated by XRD.
TL;DR: In this article, the sensitivity of surface oxidation and surface roughness to transient pool boiling heat transfer was investigated by performing water quenching experiments of Zircaloy-4 rodlets under increased pressure or subcooled water.
TL;DR: In this article, two Q&P models (QP-LE and QP-PE) were proposed to simulate the kinetics of martensite/austenite interface migration and carbon partitioning in the Fe-C-Mn-Si steels.
TL;DR: In this article, the volume fraction of age hardening precipitates upon peak ageing after different quenching rates has been studied for five Al-Zn-Mg-Cu alloys using small angle X-ray scattering (SAXS) and transmission electron microscopy (TEM).
18 Apr 2018-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this paper, a low carbon steel microalloyed with Nb-V-Ti was heat treated by means of two-step quenching and partitioning (Q&P) process after partial austenitization.
Abstract: A low carbon steel microalloyed with Nb-V-Ti were heat treated by means of two-step quenching and partitioning (Q&P) process after partial austenitization. Combined use of SEM equipped with EBSD, XRD and TEM showed that the microstructure was composed of intercritical polygonal ferrite, tempered lath martensite, secondary twin martensite and carbon-enriched retained austenite, as well as microalloyed carbides (mainly VC) precipitated inside ferrite and martensite. When increasing partitioning time from 0 s to 3600 s, the volume fraction of retained austenite increased up to 6.5% with mean carbon content in austenite keeping a constant level. The retained austenite kept K-S orientation relationship with adjacent tempered lath martensite and neighboring secondary twin martensite in different martensite packet. As partitioning time increased up to 3600 s, the initial lath martensite tempered gradually to ferrite without any cementite formation.
TL;DR: In this paper, the effects of liquid subcooling, material properties and surface conditions on the film pool boiling heat transfer using stainless steel (SS), zirconium (Zr), and Inconel-600 rods were explored.
05 Jan 2018-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this paper, the carbon partitioning during continuous cooling at different cooling rates using dilatometer was studied and an interesting phase transition was observed involving multiple stages of transformation during dynamic partitioning and a mechanism was proposed to explain the observations.
Abstract: We have studied here the carbon partitioning during continuous cooling at different cooling rates using dilatometer. An interesting phase transition was observed involving multiple stages of transformation during dynamic partitioning and a mechanism was proposed to explain the observations. Two morphologies of nano-sized retained austenite were observed, film-like and block-type. It was proposed that the amount of retained austenite was stable in a certain range of cooling rate. When the cooling rate was between 0.05 °C/s and 1 °C/s, the carbon partitioning was adequate and ~ 11 to 14% retained austenite was obtained. With increase in cooling rate from 5 and 10 °C/s, carbon partitioning was not adequate, which resulted in decrease in film-like austenite. The austenite adjacent to ferrite had two different transformation products, M/A (martensite-austenite island) and twin martensite, based on the degree of carbon transfer from ferrite. However, macro-hardness test showed that cooling rate had little effect on hardness and the hardness was between 398 HV and 407 HV at cooling rate of ~ 0.05 to 10 ℃/s. Additionally, samples cooled at low cooling rate indicated continuous TRIP effect and excellent combination of high strength 1030 MPa and high elongation of ~ 25% was obtained in the plate cooled at 0.1 ℃/s. On the basis of results, a strategy was proposed to obtain high performance hot rolled Q&P steels. The study confirmed the viability of implementing quenching and partitioning process in the hot rolling production line.
TL;DR: In this article, a boron-added low carbon steel quenched from the austenite state at different temperatures was investigated quantitatively using three-dimensional atom probe.
TL;DR: In this paper, two non-ergodic relaxor NBT-BT compositions at the morphotropic phase boundary were investigated and shown to exhibit a stabilization of ferroelectric order upon quenching.
Abstract: Recently, quenching lead-free non-ergodic relaxor Na1/2Bi1/2TiO3-BaTiO3 (NBT-BT) materials has been reported to increase the thermal depolarization temperature and enhance the lattice distortion. Driven by the conjecture that enhanced lattice distortion is typically associated with the onset of ferroelectric order, two non-ergodic relaxor NBT-BT compositions at the morphotropic phase boundary were investigated. As evident from the temperature-dependent permittivity, both compositions exhibit a stabilization of ferroelectric order upon quenching. An increase in the depolarization temperature by 40–60 °C is observed. Moreover, the composition with higher tetragonality undergoes a spontaneous relaxor-ferroelectric transition upon quenching. Annealing in oxygen atmosphere is shown to revert back the quenching-induced ferroelectric order to the relaxor state.Recently, quenching lead-free non-ergodic relaxor Na1/2Bi1/2TiO3-BaTiO3 (NBT-BT) materials has been reported to increase the thermal depolarization temperature and enhance the lattice distortion. Driven by the conjecture that enhanced lattice distortion is typically associated with the onset of ferroelectric order, two non-ergodic relaxor NBT-BT compositions at the morphotropic phase boundary were investigated. As evident from the temperature-dependent permittivity, both compositions exhibit a stabilization of ferroelectric order upon quenching. An increase in the depolarization temperature by 40–60 °C is observed. Moreover, the composition with higher tetragonality undergoes a spontaneous relaxor-ferroelectric transition upon quenching. Annealing in oxygen atmosphere is shown to revert back the quenching-induced ferroelectric order to the relaxor state.
TL;DR: In this article, the effect of a destabilization treatment combined with a subcritical diffusion and a subsequent quenching (Q) steps on precipitation of secondary carbides and their influence on the wear properties of HCCI (16%Cr).
Abstract: This work evaluates the effect of a destabilization treatment combined with a subcritical diffusion (SCD) and a subsequent quenching (Q) steps on precipitation of secondary carbides and their influence on the wear properties of HCCI (16%Cr). The destabilization of the austenite at high temperature leads to a final microstructure composed of eutectic and secondary carbides, with an M7C3 nature, embedded in a martensitic matrix. An improved wear resistance was observed in the SCD + Q samples in comparison with the Q one, which was attributed to the size of secondary carbides.
16 May 2018-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this paper, the effect of intercritical annealing temperature on retained austenite is studied using interrupted tests, and the mechanical stability of retained Austenite at uniaxial tension and plane strain states is further investigated, to understand the transformation of retainedAustenite.
Abstract: Proper mechanical stability in retained austenite is a crucial factor for medium Mn steel to attain high strength and excellent ductility. In this paper, intercritical annealing and quenching and partitioning (IA & Q&P) processes are applied to medium Mn steel, to obtain retained austenite with proper mechanical stability. The effect of intercritical annealing temperature on mechanical stability of retained austenite is studied using interrupted tests. Moreover, from the perspective of usage of medium Mn steel, the mechanical stability of retained austenite at uniaxial tension and plane strain states is further investigated, to understand the transformation of retained austenite. Results indicate that high intercritical annealing temperature (680 °C) caused the austenite to transform immediately, due to the limited resistance of austenite to martensite transformation, caused by low carbon (C) content. This low C content also led to low stacking-fault energy, which may be another way to promote the transformation of austenite. Additionally, due to the high Schmid factor, caused by enhanced grain rotation and strain state, the retained austenite has relatively low stability at the early stage of the plane strain state. With increasing martensite surrounding the austenite, the retained austenite achieves high mechanical stability at the later stage of the plane strain state.
TL;DR: Interestingly, MAPbI3 single crystal with higher crystalline quality shows a lower photoluminescence emission and a shorter decay time, indicating the surface imperfection plays an important role to the photolUMinescence.
Abstract: Halide perovskites have recently been a star semiconductor material in photovoltaic field owing to their excellent optoelectronic properties. An in-depth understanding of the photoluminescence and carrier diffusion in these materials may facilitate the implementation of high-performance optolelctronic devices. Here, we report an unusual photoluminescence quenching phenomenon in MAPbI3 single crystals. Interestingly, MAPbI3 single crystal with higher crystalline quality shows a lower photoluminescence emission and a shorter decay time, indicating the surface imperfection plays an important role to the photoluminescence. The quick quenching process is attributed to the synergistic effect of localized effect at the defects and rapid inward diffusion.
TL;DR: In this paper, a two-step quenching and partitioning steel exhibits ductile fracture under uniaxial tension and unexpectedly intergranular brittle fracture in the case of pre-cracked configuration.
TL;DR: In this paper, the effect of oxygen addition on microstructures and mechanical properties of Ti-7.5Mo (wt.%) alloy has been investigated by means of X-ray diffraction, scanning electron microscope, as well as transmission electron microscope.
TL;DR: In this article, the effects of reversion ageing on hardness, resistivity, positron lifetime, and dissolution signal were measured in a 2-week period. But the results were limited to the most reverted state, which still contained enough clusters to trap positrons efficiently and contribute to hardness.
TL;DR: The synthesis method and the techniques used for charactering the structure of nanoglasses are described together with current understanding of their salient microstructural features to constitute a distinct new class of amorphous materials.
Abstract: Nanoglasses represent a novel structural modification of amorphous materials, exhibiting properties and structural details that are markedly different from those observed in metallic glasses prepared by rapid quenching. In this review, the synthesis method and the techniques used for charactering the structure of nanoglasses are described together with our current understanding of their salient microstructural features. It is believed that the structure of nanoglasses consists of two distinct amorphous regions give rise to mechanical, thermal, and magnetic properties that are significantly different from those observed in rapidly quenched (RQ) metallic glasses. Nanoglasses, therefore, constitute a distinct new class of amorphous materials and thus opening up new opportunities for their potential use in a number of structural and functional applications.
TL;DR: In this article, the microstructure, phase components, carbon distribution, and hardness of the white and dark layers of AISI 52100 steel with PCBN inserts were analyzed via scanning electron microscopy, X-ray diffraction, electron probe microanalysis, nanoindentation, and transmission electron microscope.
TL;DR: In this article, a linear correlation was proposed between the increase ratio of the critical heat flux (CHF) and the square of the wicking number that quantifies the surface wickability.