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Microstructural Stability and Creep Performance of a Novel Low-Cost Single Crystal Superalloy
Z. H. Tan,X. G. Wang,Y. L. Du,Y. M. Li,Y. H. Yang,J. L. Liu,J. D. Liu,J. G. Li,Y. Z. Zhou,X. F. Sun 대한금속·재료학회 2022 METALS AND MATERIALS International Vol.28 No.7
The increasing pursuit of advanced aero-engines with lower ratio between the cost and performance has greatly promotedthe demanding of single crystal superalloys characterized by low cost and outstanding temperature capability. In this study,a novel low-cost single crystal superalloy was designed and the creep tests as well as micro-characterization were carried outon the experimental alloy. The results illustrated that the novel single crystal alloy exhibited an ideal microstructural stabilitywithout precipitating TCP phases, after long-term thermal exposure at the ultimate service temperature of third generationsingle crystal superalloys. Moreover, the experimental alloy with only 3 wt% Re addition demonstrated remarkable creepresistance and maintained a very low minimum creep rate at 1100 °C/137 MPa and 1120 °C/137 MPa, while the accumulationand coalescence of micro-pores had eventually led to the alloy fracture. Apart from that, the compact interfacial dislocationnetworks the 2nd γ′ phase were observed after high-temperature creep rupture, and the typical a < 010 > superdislocationswith relatively poor mobility was found at 1120 °C. At 760 °C/800 MPa, both the minimum creep velocity and entire creepstain was increased evidently, however, the ultimate creep rupture life of the alloy had still reached 200 h. The correspondingdeformation mechanism was identified as the combination of superdislocation pairs shearing and a/3 < 121 > partial dislocationcutting the γ′ phase with a SISF being generated. In general, the novel single crystal alloy characterized by remarkablemechanical properties and cost reduction possesses a great potential for future application in the advanced aircraft engines.
재래 흑돼지와 중국 재래돈간의 Melanocortin Receptor 1(MC1R) 유전자의 유전자형 분석
이성수,양보석,정진관,고서봉,오성종,양영훈,김규일,이찬동,풍서당 한국동물자원과학회 2001 한국축산학회지 Vol.43 No.1
PCR-RFLP analysis of Melanocortin receptor 1 (MC1R) gene was carried out to investigate the genotype distribution in Korean-Native and Chinese-Native pig breeds(Neijiang, Putian, Wannanhua and Jinhua). Allelic variants of MC1R in pigs were analyzed by digestion of BspH I , AccII and Hha I . Ncijiang. Wannanhua and Jinhua had only MC1R*2 allele which is considered to be typical genotype for Meishan and Large Black. Among 20 Korean-Native Pigs and 5 Putian pigs, 10 and 2 heads had the MC1R*3 allele (*2/3 or 3/3), respectively, which was detected in European pig breeds such as Hampshire, Large White, and Pietrain. The remaining animals possessed the genotype MC1R*2/2, probably reflecting the genetic introgression of MC1R*3 allele into Korean-Native and Putian pig breeds by the crossbreeding for improvement. The alleles MC1R*l and MC1R*4, which are considered to be typical allele for European Wild Boar with wild-type coat color and Duroc with red coat color, respectively, were not detected in pig breeds used in this experiment. These results indicate that the analysis of genotype frequencies of MC1R gene may be a useful tool for the conservation of Korean-Native and Chinese-Native pig breeds.
Al_(2)O_(3)-MgO계 캐스터블 내화물의 내침식성 향상
전명곤,연상흠,양정훈,김재준,황규홍,정두화 慶尙大學校 經營行政大學院 2004 工學硏究院論文集 Vol.20 No.-
To improve the mechanical and chemical properties of unfired Al_(2)O_(3) castables which is widely used in metal line of steel-making ladle, the ρ-Al_(2)O_(3) and /or fine MgO was added as a matrix powders and the degree of spinel formation was studied. Because the spinel was formed at the contact areas between Al_(2)O_(3) and MgO particles and the volume of in-situ formed spinel increased more abnormally at the site of Al_(2)O_(3) particles than MgO side, Al_(2)O_(3) aggregates was more recommendable than MgO aggregates. And to compare the degree of spinel formation in the Al_(2)O_(3)-MgO castable refractories, ultrafine SiO_(2) and Al_(2)O_(3) powders were added and their effects on physical properties such as permanent volume expansion and cold crushing strength were examined. For ρ-Al_(2)O_(3) binder, it could be replaced the alumina cement so that the CaO content could be reduced, but low compressive strength and firing shrinkage inhibit it's application to castables. But MgO powders should be added and the finer the MgO powder, the better the residual expansion and in-situ Spinel formation was observed. And due to Spinel formation and dense microstructure, CA_(6) phase would not formed around alumina aggregates during corrosion so that the corrosion resistance was much more increased.
Effect of welding residual stress redistribution on the Charpy absorbed energy
Yang, Z.,Ha, S.,Jang, B. S.,Lee, Y. 대한기계학회 2018 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.32 No.9
<P>Small specimens enclosing the welded joint are cut out when inspection for the welded joint is carried out. The cutting, however, always leads to the redistribution of residual stresses developed in the original welded joint. This study investigated the difference between the primary and secondary absorbed energy of the welded joint. The primary absorbed energy is the absorbed energy when as-weld residual stress (RS) is present. The secondary absorbed energy indicates the absorbed energy when as-weld RS in the welded joint was redistributed by the wire-cutting (WC) process. Finite element (FE) simulation of the plate welding, WC, and Charpy V-notch (CVN) test was performed to examine the effect of residual stress redistribution on the absorbed energy. Results showed that the secondary absorbed energy was, on an average, 7.8 % lower than the primary absorbed energy. This difference indicates that the primary absorbed energy of the welded joint has been underestimated from the perspective of an inspector. The difference in primary and secondary absorbed energy may not be negligible when designing large welded structures such as large pipelines.</P>
Yang, S.,Yan, X.,Yang, K.,Fu, Z. Pergamon Press [etc.] 2016 Vacuum Vol.131 No.-
This manuscript reports the synthesis of nanoscale Al<SUB>2</SUB>O<SUB>3</SUB>-reinforced Al<SUB>0.4</SUB>FeCrCoNi<SUB>1.2</SUB>Ti<SUB>0.3</SUB> high entropy alloy composites (HEACs) by mechanical alloying (MA) and spark plasma sintering (SPS). The effects of 12 wt% Al<SUB>2</SUB>O<SUB>3</SUB> on the microstructure and mechanical properties were investigated. A major FCC phase along with BCC and Al<SUB>2</SUB>O<SUB>3</SUB> were observed after SPS. Many deformation twinnings were found in HEACs from the SAED pattern. In the composite with 12 wt% Al<SUB>2</SUB>O<SUB>3</SUB> quality fraction, the fracture strength, plastic strain and Vickers hardness of HEACs were as high as 2250 +/- 10 MPa, 20.0 +/- 0.50% and 743 +/- 12Hv, respectively.
Yang, Z.,Cui, Y.,Ni, W.,Kim, S.,Xuan, Y. Springer Science + Business Media 2017 JOURNAL OF CANCER RESEARCH AND CLINICAL ONCOLOGY Vol.143 No.2
<P>Targeting Gli1, a potential diagnostic marker of ESCC stem cells, will have a profound therapeutic and prognostic value.</P>
Properties of Permeable Concrete Substrate Having Dual Pore Structures
Yang, Z. X.,Hwang, Kyu Hong,Yoon, Jeong Bae,Kim, J.O.,Kim, M.C. Trans Tech Publications, Ltd. 2008 Materials science forum Vol.569 No.-
<P>Porous concretes with continuous voids have been gaining more interest as an ecological material because of their useful functions such as water permeability and adsorption ability. Especially, to make porous concrete much more environmentalized, micropores play a role of nest for microorganism and germs to live in. So micropore distribution and the size of micropores especially open pores are the key point . In this study, the size and distribution of micropores of porous concrete were effected by the AE agents to the cement pastes and then by the treating types, treating times, treating temperatures, and the vacuum pressure during the treating. And another group specimens were added sodium bicarbonate and alum. And then physical properties were examined, digital microscope was also used to observe the micropores sizes and distributions. Cracks were observed on the cement-aggregate joint when the amount and vacuum pressure increased. And high treating temperature shows no good on the bonding of cement paste and aggregate.</P>
Reaction sintering and microstructures of zirconia/metal mixed powders
Z.X. Yang,황규홍,이종국,전병세,김환 한양대학교 세라믹연구소 2007 Journal of Ceramic Processing Research Vol.8 No.4
Reaction-sintered zirconia ceramics with a low firing shrinkage were prepared from ZrO2/Al/MgAl powder mixtures by reaction sintering and the effect of the milling characteristics of the raw powders was investigated. The powder mixtures of flaky Al with Ca-PSZ were not effectively comminuted by attrition milling compared with the alumina mixtures. However by using alumina balls rather than zirconia balls the grinding efficiency of attrition milling could be greatly increased. By contrast to fused Ca-PSZ powders natural baddeleyite was much more easily pulverized with MgAl powders. During heating, Mg and Al firstly became to oxide and subsequently converted to spinel (MgAl2O4) and finally the unreacted MgO seemed to stabilize the zirconia. The oxides which formed in the oxidation process had a very fine grain size so that the reaction sintering was more effective in densification and producing a homogeneous microstructure. The mechanical properties of the reactionsintered stabilized zirconia/spinel composite were better than those of the zirconia composite only stabilized by MgO.