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Junru Li,Jianjun Liu,Bo Jiang,Chaolei Zhang,Yazheng Liu 대한금속·재료학회 2017 METALS AND MATERIALS International Vol.23 No.2
The dissolution process of delta ferrites and the influence of high temperature pre-deformation on the dissolutionrate of delta ferrites in martensitic heat-resistant steel 10Cr12Ni3Mo2VN were studied by isothermalheating and thermal simulation experiments. The precipitation temperature of delta ferrites in experimentalsteel is about 1195 °C. M23C6-type carbides incline to precipitate and coarsen at the boundaries of delta ferritesbelow 930 °C, and can be rapidly dissolved by heating at 1180 °C. The percentage of delta ferrites graduallydecreases with heating time. And a Kolmogorov-Johnson-Mehl-Avrami equation was established to describethe dissolution process of delta ferrites at 1180 °C. High temperature pre-deformation can markedly increasethe dissolution rate of delta ferrites. Pre-deformation can largely increase the interface area between delta ferriteand matrix and thus increase the unit-time diffusing quantities of alloying elements between delta ferritesand matrix. In addition, high temperature pre-deformation leads to dynamic recrystallization and increases thenumber of internal grain boundaries in the delta ferrites. This can also greatly increase the diffusing rate ofalloying elements. In these cases, the dissolution of delta ferrites can be promoted.
Bo Jiang,Zhen Mei,Leyu Zhou,Chaolei Zhang,Yazheng Liu 대한금속·재료학회 2016 METALS AND MATERIALS International Vol.22 No.4
Based on 42CrMo steel, a steel with a higher C and Ni content is developed for use in large sized bearing rings. The impact energy and hardness of the quenched and tempered steel increase with the quenching temperature, but then decrease when the temperature is above 925 °C. When the temperature is below 925 °C, some larger M23C6-type carbides (with average diameters of 255.6 μm) exist in the quenched and tempered microstructure. The number of carbides is reduced as the quenching temperature increases. At the same time, the fracture modes change from microvoid coalescence and quasi-cleavage to microvoid coalescence. The number of round quasi-cleavage fractures, which are formed around the carbides, decrease as the number of carbides decrease. The existence of larger M23C6-type carbides leads to round quasi-cleavage fractures and decrease the impact energy. The precipitation strengthening of M23C6-type carbides increases the hardness at a quenching temperature of 925 °C.
Banpu Ruan,Zhenyu Gao,Juan Zhao,Bin Zhang,Anpeng Zhang,Kai Hong,Shenglong Yang,Hongzhen Jiang,Chaolei Liu,Guang Chen,Youlin Peng,Guojun Dong,Longbiao Guo,Zhengjin Xu,Qian Qian 한국식물학회 2017 Journal of Plant Biology Vol.60 No.4
Leaf color-related mutants are important materialsto study the chlorophyll biosynthesis and chloroplastdevelopment. Here, we isolated and characterized a thermosensitiveyellow-green leaf mutant, ygl, through mutagenizedJaponica rice cultivar Zhonghua11 by EMS. The mutantshowed yellow-green leaves only at the seedling stage. Genetic and molecular analyses uncovered that YGL encodean Mg2+-chelatase ChlD subunit, which was a new allele ofChl1/YGL7. Quantitative PCR and GUS staining showedthat the YGL transcripts expressed in all tested organs andsubcellular localization detected YGL protein in the chloroplasts. The mutant displayed yellow-green leaves at 20°C andnormal green leaves at 34°C during the seedling stage. Transcript level of YGL in the ygl mutant was significantlyreduced at 20°C, and increased at 34°C compared with thewild-type plant. Furthermore, the expression of chlorophyllbiosynthesis and chloroplast development related genes wereinfluenced by the mutation of YGL at different temperature. These findings suggested that the YGL gene not only play akey role in chlorophyll biosynthesis, but is affected attranscript level by temperature in rice.