http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
Effect of Vibration on Microstructures and Mechanical Properties of 304 Stainless Steel GTA Welds
Chih-Chun Hsieh,Chien-Hong Lai,Weite Wu 대한금속·재료학회 2013 METALS AND MATERIALS International Vol.19 No.4
This study investigates the microstructures and mechanical properties of 304 stainless steel at various vibration frequencies during simultaneous vibration welding. The experimental results demonstrated that simultaneous vibration welding could accelerate the nucleation and grain refinement of the microstructures. The effect of the grain refinement was more evident at the resonant frequency (375 Hz) and a minimum content of residual δ-ferrite (4.0%). The γ phase grew in the preferential orientation of the (111)direction with and without vibration. The full width at half maximum of the diffraction peak widened after the vibration, which was attributed to the grain refinement. The residual stress could be efficiently removed through simultaneous vibration welding when the amplitude of the vibration was increased. Furthermore, the lowest residual stress (139 MPa) was found when the vibration frequency was 375 Hz. The hardness and Young’s modulus exhibited slight increases with low and medium frequencies. The hardness values were increased by 7.6% and Young’s modulus was increased by 15% when the vibration frequency was resonant (375 Hz).
Effect of a Carbon Additive on the TbCu7-type Melt-spun Sm(Co, M)7 (M=Ti, Zr, Hf, V and Ge) Ribbons
Chih-Chieh Hsieh,Shih-Teng Huang,Jin-Sheng Guo,Chih-Wei Shih,Wen-Cheng Chang,Huang-Wei Chang,Chun-Chung Shaw 한국물리학회 2013 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.63 No.3
The effect of a carbon additive on the microstructure and the magnetic properties of melt-spunSmCo7−xMxCy (M=Ti, Zr, Hf, V and Ge; x = 0 - 0.3 and y = 0 - 0.1) ribbons was studied. Based on the XRD and the TEM analyses, a pure 1:7 phase could be formed for the C-containingribbons with M= Ti and Ge. However, carbide phases, i.e., Sm2C3 for M=Zr and Hf, and SmCoC2for M=V, respectively, were found. Nevertheless, a slight C addition may effectively refine themicrostructure and improve both the intrinsic coercvity and the magnetic energy product in all thestudied ribbons. Among them, the SmCo6.9V0.1C0.1 ribbons with r = 58.7 emu/g, iHc = 13.5kOe and (BH)max = 9.3 MGOe, and the SmCo6.9Hf0.1C0.1 ribbons with r = 61.6 emu/g, iHc =11.8 kOe and (BH)max = 10.3 MGOe are most suitable for the bonded magnet applications.
Chih-Chun Hsieh,Xiaofei Guo,Chia-Ming Chang,Weite Wu 대한금속·재료학회 2010 METALS AND MATERIALS International Vol.16 No.3
The purpose of this study is to discuss the development of dendrite δ-ferrite and the precipitation behavior of σ phase in the overlapping heat-affected zones, or the fusion zones, during the multipass dissimilar stainless steels welding process. The color metallographic and color separation techniques were used to clearly identify the δ, σ, and γ phases. The experimental results indicated that the grain refinement was very obvious in the second and third pass fusion zones (304-1 and 304-2) when the welding pass was increased from 1 to 3. This refining phenomenon was attributed to the higher cooling rate and the degree of supercooling. The δ phase precipitated in the secondary and the tertiary dendrite arms of the δ-ferrite and it was able to grow on the dendrite arms along the [111] crystallographic in a 45o angle. The σ phase was also able to form stably after the phase decomposition of δ-ferrite into globular and lacy morphologies.
Chih-Chun Hsieh,Yi-Chia Liu,Jia-Siang Wang,Weite Wu 대한금속·재료학회 2014 METALS AND MATERIALS International Vol.20 No.4
The aim of this study is to discuss the effect of microstructural development with different Ti contents inFe-based hardfacing alloys. A series of Fe-Cr-C-Si-Mn-xTi alloy fillers was deposited on SS400 low carbonsteel substrate using oscillating gas tungsten arc welding. The microstructure in the Fe-based hardfacing alloywithout Ti content addition included: the primary γ, eutectic γ+(Fe,Cr)3C, eutectic γ+(Fe,Cr)2C and martensite. With increasing Ti contents, the microstructures showed the primary TiC carbide, γ phase and eutectic+(Fe,Cr,Ti)3C. The amount and size of TiC carbide in the hardfacing layers increased as the Ti contentincreased. However, the eutectic γ+(Fe,Cr,Ti)3C content decreased as the Ti content increased. Accordingto the results of the hardness test, the lowest hardness value (HRC 54.93) was found with 0% wt% Ti andthe highest hardness (HRC 60.29) was observed with 4.87 wt% Ti.
Microstructural Development of Brass Alloys with Various Bi and Pb Additions
Chih-Chun Hsieh,Jia-Siang Wang,Paxon Ti-Yuan Wu,Weite Wu 대한금속·재료학회 2013 METALS AND MATERIALS International Vol.19 No.6
In the study, using the gravity casting method, adding 1.52%Pb, 0.5%Bi, 1%Bi and 1.5%Bi into the brass (Cu- 40%Zn) alloy. The microstructural changes from the Widmanstätten into the networked structures when Pb was added to 1.5%. The microstructure was an acicular Widmanstätten when Bi contents were 0.5% and 1% and it was a plate Widmanstätten when Bi contents were 1.5%. There were four kinds of precipitation morphologies of Bi particles. The precipitation morphologies of Bi particles can be divided into a globular (<1 μm), a disc (=1 μm), discontinuous massive (>1 μm), and continuous block structures (about 20~30 μm). The Pb particles were embedded in the networked α phase and the Bi particles precipitated at the α/α and the α/β’ grain boundaries. The XRD analysis showed the high proportion of β’ phase with 0.5% Bi-brass and 1% Bi-brass and indicated a lower one with Pb-brass and 1.5% Bi-brass.
( Chih Chun Hsieh ),( Tao Chih Chang ),( Dong Yih Lin ),( Ming Che Chen ),( Wei Te Wu ) 대한금속재료학회 ( 구 대한금속학회 ) 2007 METALS AND MATERIALS International Vol.13 No.5
The purpose of this study is to investigate the precipitation characteristics of σ phase in the fusion zone of stainless steel welds at various welding passes during a tungsten arc welding (GTAW) process. The morphology, quantity, and chemical composition of the δ-ferrite and σ phase were analyzed using optical microscopy (OM), a ferritscope (FS), a X-ray diffractometer (XRD), scanning electron microscopy (SEM), an electron probe micro-analyzer (EPMA), and a wavelength dispersive spectrometer (WDS), respectively. Massive δ-ferrite was observed in the fusion zone of the first pass welds during welding of dissimilar stainless steels. The σ phase precipitated at the inner δ-ferrite particles and decreased δ-ferrite content during the third pass welding. The σ and δ phases can be stabilized by Si element, which promoted the phase transformation of δ→σ + γ2 in the fusion zone of the third pass welds. It was found that the σ phase was a Fe-Cr-Si intermetallic compound found in the fusion zone of the third pass welds during multi-pass welding.
Phase Transformations of 24Cr-14Ni-0.7Si Stainless Steel under Different Aging Conditions
Chih-Chun Hsieh,Dong-Yih Lin 대한금속·재료학회 2010 METALS AND MATERIALS International Vol.16 No.2
This study discusses the development of a phase transformation in 24Cr-14Ni-0.7Si stainless steel after aging under various aging temperatures, times, and N2/Air ratios. The observation of OM indicated that the initial state of δ-ferrite in the test material appeared as complete dendrite structures at short aging times and then exhibited lacy and dispersed structures when the aging time increased. This led to a gradual austenitization transformation as the nitrogen/air ratio increased, accelerating the δ/σ phase transformation and retarding the δ/γ phase transformation at the same time. The δ/σ phase transformation was dominant when the aging temperature was 800 °C. A line scanning analysis of the EPMA showed that the X-ray spectrum of Cr at the δ/γ interphase boundary was raised. In addition, Si showed lower X-ray spectrum energy after the δ/γ phase transformation. Clearly, Si had a stabilizing effect on the δ-ferrite and σ-phase. Furthermore, it had the fastest precipitation ratio for the δ/σ phase transformation at 800°C among all aging temperatures.
Chih-Chun Hsieh,Ming-Shou Shi,Weite Wu 대한금속·재료학회 2012 METALS AND MATERIALS International Vol.18 No.1
The purpose of this study is to discuss the effect of annealing temperatures on growth of intermetallic phases in Al/Cu composites during the accumulative roll bonding (ARB) process. Pure Al (AA1100) and pure Cu (C11000) were stacked into layered structures at 8 cycles as annealed at 300 °C and 400 °C using the ARB technique. Microstructural results indicate that the necking of layered structures occur after 300 °C annealing. Intermetallic phases grow and form a smashed morphology of Al and Cu when annealed at 400 °C. From the XRD and EDS analysis results, the intermetallic phases of Al2Cu (θ) and Al4Cu9 (γ2) formed over 6 cycles and the AlCu (η2) precipitated at 8 cycles after 300 °C annealing. Three phases (Al2Cu (θ), Al4Cu9 (γ2), and AlCu (η2)) were formed over 2 cycles after 400 °C annealing.
( Chih Chun Hsieh ),( Dong Yih Lin ),( Wei Te Wu ) 대한금속재료학회 ( 구 대한금속학회 ) 2007 METALS AND MATERIALS International Vol.13 No.5
The dispersion strengthening behavior of the σ phase in 304 modified stainless steel as hot-rolled at 1073 K has been investigated in this study. The morphology, quantity and chemical composition of the σ phase were analyzed using optical microscopy (OM), X-ray diffractometry (XRD), ferritscope (FS), and image analysis (IA). The amounts of σ phase in the stainless steels increased gradually at 1073 K as the reduction ratio increased from 0% to 75%. The XRD analyses showed that a higher reduction ratio enhanced the conversion of δ-ferrite (110) to σ phase (542). The σ phase was precipitated homogeneously at the recrystallized ferrite grains when the reduction ratio was increased from 0% to 75%.