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RISS 인기검색어
- 검색키워드
- 저자 : Huiqin Chen (검색결과 4 건)
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Behavior and Mechanism of Void Welding Under Thermal Mechanical Coupling
Fei Chen,Xitao Wang,Huiqin Chen,Shue Dang 대한금속·재료학회 2022 METALS AND MATERIALS International Vol.28 No.7
Shrinkage cavity, microporosity, blowhole and the likes are the typical void defects in ingot. Only through reasonable hightemperature deformation and heat preservation process can the void defects be closed and welded to ensure the high qualityof forgings. However, there are few researches on the welding behavior of voids, and the understanding of the void weldingmechanism is still insufficient. In order to further study the welding behavior of void and explore the welding mechanism,the welding process of void and microstructure evolution around void under thermal mechanical coupling were studied byphysical simulation. The results show that heating temperature, holding time, plastic deformation play an important role invoid welding. The void welding degree increases with the increase of heating temperature, holding time and plastic deformation. Besides, there are three main welding mechanisms for void defects, including the volume of microvoids decreasesdue to vacancy diffusion, the void welding mechanism caused by the austenite-ferrite transformation at lower temperaturesand the void welding mechanism caused by recrystallization and grain growth of austenite grains at higher temperatures.
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Physically-Based Constitutive Modelling of As-Cast CL70 Steel for Hot Deformation
Fei Chen,Xiaodong Zhao,Jinyu Ren,Huiqin Chen,Xiaofeng Zhang 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.6
In order to conduct numerical simulation of plasticity forming and confirm the processing parameters of heat deformationfor as-cast CL70 steel, the hot deformation behaviors of as-cast CL70 steel were studied by isothermal compression testswhich used a Gleeble-1500D thermal mechanical simulation tester for the deformation temperatures ranging from 1173 to1523 K and the strain rates ranging from 0.001 to 1 s−1. Flow stress curves of the steel were obtained under high temperature. The flow stress constitutive models of the work hardening-dynamical recovery period and dynamical recrystallizationperiod were established for as-cast CL70 steel. In work hardening-dynamic recovery period, the flow stress was predicted byemploying the evolution rule of dislocation density in the constitutive model. In dynamic recrystallization period, the flowstress after the critical strain was predicted by employing the dynamic recrystallization kinetics in the constitutive model. To improve the prediction accuracy of the model, the dynamic recovery coefficient is modified in the traditional physicallybasedconstitutive model. The results indicate that the proposed physically-based constitutive model has high accuracy inpredicting the flow stress under hot deformation for as-cast CL70 steel.
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Lingyue Tan,Silin Han,Shuhui Chen,Tao Hang,Huiqin Ling,Yunwen Wu,Ming Li 대한금속·재료학회 2021 ELECTRONIC MATERIALS LETTERS Vol.17 No.2
Thermal treatment is an effective way to decrease the resistivity and internal stress by inducing grain growth accompaniedwith redistribution of embedded impurities. With the narrowing of Cu interconnects in IC packaging, the increased resistanceis becoming the main issue that hindering the electrical performance of IC. Herein, a laser annealing method by linerscanning (LALS) to anneal the Cu interconnects were reported which provide a gradient thermal field for the crystallographic/microstructure transition. The impacts of laser annealing on the sheet resistance of the electroplating Cu films wereinvestigated in aspects of microstructure and phase field simulation. Cu films treated by LALS owned larger average grainsize, better recrystallization fraction, and significantly higher average grain aspect ratio than conventional annealing, whichindicated the increased driving force for grain boundaries evolution by LALS method. This study exhibited the direct evidenceon the impacts of laser annealing process on the resistance of electroplated Cu films. The laser annealing process witha local temperature gradient caused a significant decline in Cu electrical resistance compared to the conventional annealingprocess, indicating its extraordinary potential in improving Cu wire conductivity. This work will provide a scientific basis forselecting the post-treatment process for electrodeposited Cu films to achieve ideal electrical properties and microstructurein electronics industry applications.
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Fengming Qin,Yajie Li,Wenwu He,Xiaodong Zhao,Huiqin Chen 대한금속·재료학회 2017 METALS AND MATERIALS International Vol.23 No.6
The aging precipitation behavior in Mn18Cr18N austenitic stainless steel was investigated at temperatures from600 °C to 900 °C. During isothermal aging treatment, the primary precipitate was Cr2N with a = 0.478 nm and c =0.444 nm, and it preferentially nucleates along initial grain boundaries and gradually grows towards the interior ofgrains in discontinuous cellular way. Meanwhile, a small amount of granular face-centred cubic M23C6 with a =1.066 nm also were observed, which mainly form along grain boundaries. The effect of these precipitates onmechanical properties of the alloy was studied. It was found that precipitates result in degeneration of the matrixhardness. Meanwhile, the SEM morphologies of aged tensile sample show that the brittle fracture predominatesduring deformation, i.e. the fracture mode transforms from intergranular fracture to transgranular fracture with theincreasing of aging time. Compared with the solution-treated sample, the strength of the aged tensile samplesslightly decreases and plasticity remarkably deteriorates.
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