http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
고온자전 합성법에 의해 제조된 TiNiFe합금에서 Incommensurate 상의 형성
조재섭,김도향,김용석,Cho, Jae-Seob,Kim, Do-Hyang,Kim, Yong-Seog 한국현미경학회 1996 Applied microscopy Vol.26 No.3
Structure of premartensite in $Ti_{50}Ni_{49}Fe_1\;and\;Ti_{50}Ni_{50}$ prepared by self-propagating high temperature synthesis (SHS) method has been investigated by a detailed transmission electron microscopy. $Ti_{50}Ni_{49}Fe_1$ consists of microdomain area and needle type domain area. On the other hand, $Ti_{50}Ni_{50}$ consists of microdomain-free and microdomain area, and needle type domain area. Various types of extra superreflections, such as 1/2<100>, 1/2<110> and 1/4<210> type superreflection have been observed in the selected area electron diffractions from microdomain area. Such extra superreflections are due to transformation from B2 structure to distorted B2 structure or premartensite. The present study shows that incommensurate phase forms as an intermediate phase during martensitic transformation. Particularly, in Fe-free $Ti_{50}Ni_{50}$, two types of matrix phases have been observed, microdomain and microdomain-free area. Types of extra superreflections in $Ti_{50}Ni_{50}$ are different from those in $Ti_{50}Ni_{49}Fe_1$, i.e. 1/7<321> type superreflections have been observed, instead of 1/2<110>, 1/2<100>, 1/4<210> types in $Ti_{50}Ni_{49}Fe_1$.
Al-Zn-Mg계 알루미늄 합금의 유동성에 미치는 합금원소의 영향
조재섭 ( Jea Sup Cho ),김지훈 ( Jee Hun Kim ),심우정 ( Woo Jeong Kim ),임항준 ( Hang Joon Im ) 한국주조공학회 2012 한국주조공학회지 Vol.32 No.3
Al-Zn-Mg alloys, being high strength aluminum alloys, have attracted attention as a material of automobile parts that require higher mechanical properties and lightness. Automobile parts with complex shapes are manufactured by low-priced casting method, but Al-Zn-Mg alloys are difficult to cast because of its poor hot cracking, feeding, and fluidity. Thus fluidity experiments on Al-Zn-Mg alloys were conducted for the castability evaluation. The effects of Mg and Zn, representative elements of Al-Zn-Mg alloys, on fluidity were observed. Spiral mold was used for fluidity experiments and the lengths of solidified specimens were measured after melting and gravity casting. Correlation between microstructures and fluidity length based on the alloy composition was considered. According to the experimental results, as the amount of Mg and Zn increased, fluidity decreased. Also, it was confirmed that fluidity change by the variation of Mg composition was greater than that of Zn.
Ti/Ni 다층계면 확산 반응에 의한 TiNi 금속간 화합물의 형성
김도향,조재섭 대한금속재료학회(대한금속학회) 1997 대한금속·재료학회지 Vol.35 No.11
Formation kinetics of TiNi intermetallics at the interface between Ti and Ni plate has been studied. Two types of the interfaces have been studied: Ni/Ti single-interface type; and Ti/Ni/Ti/Ni multi-interface type. After pressurization at 800℃ Ti₂ Ni and TiNi₃ form at the interface. Higher pressure promotes a more uniform and thicker reaction layer. TiNi intermetallic layer forms between Ti₂Ni and TiNi₃, growing steadily with time. Growth of TiNi satisfies the 'parabolic law', while thickness of Ti₂Ni and TiNi₃, remains nearly constant. In the case of Ti/Ni/Ti/Ni multi-layer interface, TiNi forms more effective y than that in Ti/Ni single-layer interface due to the cooperative growth of TiNi from neighbouring Ti₂Ni and TiNi₃. Thicknes measurement shows that TiNi forms by a volume diffusion mechanism at the interface. Calculated chemical diffusion coefficient, D^v is D^v=1.0014exp(-1148062/RT), and activation energy for the diffusion process is 1148062 J/㏖.
Ni/Ti 계면반응에 의한 NiTi 형성 : 속도론적 고찰
김용석,김도향,조재섭,홍민종 대한금속재료학회(대한금속학회) 1998 대한금속·재료학회지 Vol.36 No.8
Diffusion kinetics for growth of NiTi at Ni/Ti interface has been investigated. The temperature dependence of the intrinsic diffusion coefficient of Ni, Ti in NiTi intermetallic compound was obtained by D_(Ni)(NiTi) (㎠/sec) = 9.8401×10^(-6)·exp(-95950/RT) and D_(Ti)(NiTi)(㎠/sec) = 1.9111×10^(-5)·exp(-101730/RT). The activation energies of the intrinsic diffusion coefficients of Ni, Ti are 9.5950(±0.84)×10⁴(J/㏖) and 10.173(±3.02)×10⁴(J/㏖) respectively. The parabolic growth constant(k_p^(NiTi)(㎠/sec)) of NiTi calculated by using the equations given by Shatynski. Hirth and Rapp was 1.0797×10^(-5)·exp(-109980/RT) for the temperature range between 800 and 950℃. The activation energy of the growth rate constant is 1.0998(±0.17)×10^5(J/㏖). Present study suggests that the calculation of growth rate constants by the method of Shatynski, Hirth and Rapp can be applied successfully when the interface layer growth follows the parabolic law.
Al-Zn-Mg-Cu계 알루미늄 합금의 열간 균열 특성에 미치는 합금조성의 영향
김지훈 ( Jee Hun Kim ),조재섭 ( Jae Sub Jo ),심우정 ( Woo Jeong Sim ),임항준 ( Hang Joon Im ) 대한금속재료학회(구 대한금속학회) 2012 대한금속·재료학회지 Vol.50 No.9
Hot tearing was the most significant casting defect when the castability evaluation of the Al- Zn-Mg-Cu alloy system was conducted. It was related to the solidification range of the alloy. Therefore, the hot tear susceptibility of the AA7075 alloy, whose solidification range is the widest, was evaluated. The hot tear susceptibility was evaluated by using a mold for a hot tearing test designed to create the condition for the occurrence of hot tear in 8 steps. According to the tearing location and shape, a hot tear susceptibility index (HTS) score was measured. The solidification range of each alloy and hot tear susceptibility was compared and thereafter the microstructure of a near tear defect was observed. As a result, the HTS of the AA7075 alloy was found to be 67. Also, the HTS in relation to a change in Zn, Mg, Cu composition showed a difference of about 6-11% compared to the AA7075 alloy.