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Guoxing Qiu,Dongping Zhan,Changsheng Liu,Min Qi,Zhouhua Jiang,Huishu Zhang 한국원자력학회 2019 Nuclear Engineering and Technology Vol.51 No.5
The effects of Y and Ti on the microstructure stability and tensile properties of the reduced activationferritic/martensitic steel have been investigated. The addition of Y and Ti affected the prior austenitegrain size due to the pinning of the inclusions. Ti addition of 0.008 wt% to the steel was intended topromote the precipitation of nano-sized carbides with a high resistance to coarsening. 8Ti14Y exhibited ahigher yield strength and a lower DBTT than the other alloys due to the fine grain size and additionalprecipitation hardening by (Ti, Ta)-rich MX. After thermal exposure at 550 C for 1500 h, yield strengthwas dropped significantly in exposed 0Ti13Y. On the contrary, a lower reduction of YS was observed in8Ti14Y. The M23C6 in 0Ti13Y and 8Ti14Y and MX in 25Ti14Y and 39Ti15Y coarsened seriously duringageing, which could be responsible for the reduction of the tensile properties of alloys.
Guoxing Qiu,Dongping Zhan,Changsheng Liu,Min Qi,Zhouhua Jiang,Huishu Zhang 한국원자력학회 2019 Nuclear Engineering and Technology Vol.51 No.6
In this paper, the CLAM steel strengthened by micro-scale YeZreO was prepared by vacuum inductionmelting followed by electroslag remelting (VIM-ESR). Yttrium (Y) and zirconium (Zr) were easy to aggregatesinto massive yttrium-zirconium-rich inclusions in the steel melted by vacuum inductionmelting (VIM), which would interrupt the continuity of the matrix and reduce the mechanical propertiesof steel. Micron-sized YeZreO inclusions would be produced with the removal of original blocky YeZrrichinclusions and the submicron-sized inclusions smaller than 0.2 mm could be retained in the steel. The small grain size and the better refinement and distribution uniformity of YeZreO inclusions afterremelting would be responsible for the better yield strength and toughness. For VIM-ESR alloy, the ultimatetensile strength is 749 MPa and the yield strength is 642 MPa at room temperature, meanwhilethey are 391 MPa and 367 MPa at 600 C, respectively. Meanwhile, the ductile-brittle transition temperature(DBTT) reduced from 43 C (VIM) to-76 C (VIM-ESR).
Qiu, Guoxing,Zhan, Dongping,Li, Changsheng,Yang, Yongkun,Jiang, Zhouhua,Zhang, Huishu Korean Nuclear Society 2020 Nuclear Engineering and Technology Vol.52 No.4
Y-containing CLAM steels were melted via vacuum induction melting and electroslag remelting. In this study, the evolution, microstructure, and mechanical properties of the alloy inclusions (ESR-1 (0 wt.% Y), ESR-2 (0.016 wt.% Y) and ESR-3 (0.042 wt.% Y)) were investigated. Further, the number of inclusions in ESRed steel was observed to obviously decrease, and the distributions were more uniform. The fine Y-Al-O inclusions (1-2 ㎛) were the main inclusions in ESR-2. The addition of Y affected the prior austenite grain size (PAGZ), increasing the tensile strength at test temperature. Low ductile-brittle transition temperature (DBTT) was obtained because of the fine PAGZ and dispersive inclusions. For the ESRed CLAM steel with 0.016 wt.% Y, the yield strengths were 621 MPa at 20 ℃ and 354 MPa at 600 ℃ in air. Further, the uniform elongation and elongation of the ESR-2 alloy were 5.5% and 20.1% at 20 ℃, respectively. Meanwhile, the DBTT tested using full-size Charpy impact specimen (55 cm × 10 cm × 10 cm) was reduced to -83 ℃.
Zhou, Hua,Zhang, Jiangli Techno-Press 2014 Structural Engineering and Mechanics, An Int'l Jou Vol.52 No.2
This paper presents detailed analysis of the internal forces of interior beam-column joints of reinforced concrete (RC) frames under seismic action, identifies critical joint sections, proposes consistent definitions of average joint shear stress and average joint shear strain, derives formulas for calculating average joint shear and joint torque, and reports simplified analysis of the effects of joint shear and torque on the flexural strengths of critical joint sections. Numerical results of internal joint forces and flexural strengths of critical joint sections are presented for a pair of concentric and eccentric interior connections extracted from a seismically designed RC frame. The results indicate that effects of joint shear and torque may reduce the column-to-beam flexural strength ratios to below unity and lead to "joint-yielding mechanism" for seismically designed interior connections. The information presented in this paper aims to provide some new insight into the seismic behavior of interior beam-column joints and form a preliminary basis for analyzing the complicated interaction of internal joint forces.