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RISS 인기검색어
- 검색키워드
- 저자 : Renbo Song (검색결과 6 건)
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Solid-state Synthesis of Mg2X (X=Si, Ge, Sn and Pb) via Bulk Mechanical Alloying
Aizawa Tatsuhiko,Song Renbo 한국분말야금학회 2006 한국분말야금학회 학술대회논문집 Vol.2006 No.1
Solid-state processing via the bulk mechanical alloying enables us to directly fabricate Mg2X semi-conductive material performs. Precise control of chemical composition leads to investigation on the dilution and enrichment of X in Mg2X. Two types of solid-state reactivity are introduced: e.g. synthesis of Mg2Si from elemental mixture Mg - Si is nucleation-controlled process while synthesis of Mg2Sn from Mg - Sn, diffusion-controlled process. Thermoelectricity of these Mg2X is evaluated for discussion on the validity and effectiveness of this new PM route as a reliable tool for fabrication of thermoelectric compounds.
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Zhongzheng Pei,Renbo Song,Yifan Feng,Jie Xu 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.11
Here we utilized two cooling methods, forced air cooling and furnace cooling, to obtain two different triplex microstructureswhich were martensite-based and bainite-based, respectively. Compared with furnace cooled samples, the forced air cooledsamples presented about 5% higher ultimate tensile strength, 10% higher hardness and 43% lower Charpy impact energyvalue. Nano-indentation test was conducted to reveal the local mechanical properties. The nano-hardness of martensite,bainite and the mixture microstructure is 5.633 GPa, 4.200 GPa and 5.082 GPa, respectively. Mn, S, C and Si segregationat the grain boundaries in martensite are severely detrimental to the toughness. High rotation angle grain boundaries andprecipitates of rare earth element enhanced the toughness of bainite. Martensite with high density dislocations in fine lathsexhibited higher nano-hardness than bainite with lower density dislocations in wider sized laths. The interaction of the twophases with martensite twinning sub structure between bainite laths showed intermediate nano-hardness.
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Role of Subordinate Phases on the Dry Impact‑Abrasion Behavior of Low Chromium Cast Iron
Yu Pei,Renbo Song,Yi Li,Zhiyang Zhao,Yingchao Zhang 대한금속·재료학회 2020 METALS AND MATERIALS International Vol.26 No.12
In order to study the resistance mechanism of materials having high resistance to impact-abrasion, synergistic effect ofsubordinate phases of 2.20 wt%C–3.45 wt%Cr–3.06 wt%Mn–1.32 wt%Si–0.51 wt%Cu–0.31 wt%Ni–0.002 wt%B cast ironwas investigated under dry impact-abrasion. Subordinate phases consist of graphite, secondary precipitates and retainedaustenite. Results show that the synergistic effect of above subordinate phases can prevent matrix and carbide from peelingoff, and minimize the damage of carbide to matrix. This effect reduces the depth and width of groove from 7 to 1.2 μm andfrom 14 to 2.5 μm respectively. Above significant improvement is owing that: (1) Graphite can disperse external/internalstress, and fill carbide peeling pits. (2) Secondary precipitates, such as [Fe, Ni] and [Cr, Ni], can disperse the concentratedstress of carbide, inhibiting peeling. (3) Retained austenite can disperse the internal concentrated stress which is transferredfrom the carbide and fine precipitates to matrix.
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Yifan Feng,Renbo Song,Zhongzheng Pei,Renfeng Song,Guoyu Dou 대한금속·재료학회 2018 METALS AND MATERIALS International Vol.24 No.5
The microstructure and impact toughness of the as-cast Fe–24.8Mn–7.3Al–1.2C austenitic steel after solution treatmentand subsequent aging treatment were investigated in the present work. Research on the κ-carbides precipitation behaviorwas carried out by transmission electron microscope. The results show that nano-sized coherent κ-carbides were obtained inthe as-solutionized steel after aging treatment, which produced precipitation hardening. After being aging treated at 550 °Cfor 1 h, the steel with regular hexagonal grain structure exhibited a good combination of yield strength (~ 574 MPa) androom-temperature impact toughness (~ 168 J). In the present steel, the typical cube-on-cube orientation relationship betweenaustenite and κ-carbides was observed. However, due to the long aging isothermal time and high C content, the coarseintergranular κ′-carbide was formed and grew along the austenite grain boundary, which caused this orientation relationshipto be destroyed and a dramatical increase of the coherency strain energy at grain boundary. Furthermore, serious embrittlementof grain boundaries caused that cleavage cracks trend to propagate along the grain boundaries. Accordingly, theroom-temperature impact toughness decreased sharply. After aging isothermal time prolonging to 13 h, the Charpy V-notchimpact toughness was only ~ 5 J and fracture mode turned to fully brittle fracture accompanied with fl at facets, shear cracksand well-developed secondary crack.
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Thermoelectric Material Design in Pseudo Binary Systems of on the Powder Metallurgy Route
Aizawa Tatsuhiko,Song Renbo,Yamamoto Atsushi 한국분말야금학회 2006 한국분말야금학회 학술대회논문집 Vol.2006 No.1
New PM route via bulk mechanical alloying is developed to fabricate the solid solution semi-conductive materials with and for 0 < x, y < 1 and to investigate their thermoelectric materials. Since is n-type and both and are p-type, pn-transition takes place at the specified range of germanium content, x, and tin content, y. Through optimization of chemical composition, solid-solution type thermoelectric semi-conductive materials are designed both for n-and p-type materials.
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Yongjin Wang,Yingchao Zhang,Renbo Song,Liang Huang,Yu Pei 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.10
The effect of austenitizing temperature on microstructure evolution and impact toughness of a newly developed Fe–3.0C–2.8Si–2.0Mn–0.9V–0.2Cr bainite ductile iron was investigated in this research. The ductile iron specimens were heat treatedunder different continuous cooling process, involving austenitizing between 900 and 980 °C and followed tempering at200 °C. Optical microscopy, X-ray diffraction, scanning electron microscope and transmission electron microscope tests wereconducted to investigate the microstructure evolution. Impact toughness and Rockwell hardness were measured. The resultsshowed that the microstructure of the ductile iron mainly consisted of graphite, acicular bainite and retained austenite aftercontinuous cooling process. The austenitizing temperature could change the volume fraction and size of bainite and retainedaustenite. There existed a C-area, where retained austenite accumulated near the graphite, except for specimen austenitizedat 920 °C. The impact toughness of specimens increased first and then get worse with the increasing of austenitizing temperature. The impact toughness was related with the volume fraction of bainite and the morphology of retained austenite. The fracture mechanism of the bainite ductile iron belonged to cleavage fracture. Chunky graphite acted as the source ofmicrocrack during the impact process. The bulky retained austenite behaved as a prior path for the microcrack propagation,while the bainite and thin filmy retained austenite limited its propagation.
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