서지주요정보
γ기지 TiAl 합금 및 CP-Ti의 연속 냉각 변태 거동의 실시간 측정 = In-situ measurement of continuous cooling transformation behaviors of γ-based Ti-Al alloys and of CP-Ti
서명 / 저자 γ기지 TiAl 합금 및 CP-Ti의 연속 냉각 변태 거동의 실시간 측정 = In-situ measurement of continuous cooling transformation behaviors of γ-based Ti-Al alloys and of CP-Ti / 김성곤.
저자명 김성곤 ; Kim, Seong-Kon
발행사항 [대전 : 한국과학기술원, 2002].
Online Access 원문보기 원문인쇄

소장정보

등록번호

8013356

소장위치/청구기호

학술문화관(문화관) 보존서고

DMS 02006

휴대폰 전송

도서상태

이용가능

대출가능

반납예정일

초록정보

The real time resistivity-temperature-time measurement system has been modified to operate under high vacuum system. Present study thus allowed to estimate the environmental effect, in particular, the oxygen effect on the α→$γ_L$ lamellar reaction in T-45.5at.%Al alloy. The results of the present study are in good agreement with previous results measured under Ar+He gas atmosphere in Ti-45.5at.%Al alloy except the data at relatively slow cooling rates, i.e., at cooling rates less than about $20℃s^{-1}$. The present data showed significantly lower α→γL lamellar start temperatures at these slow cooling rates. Apart from this difference, two results are very close each other. Namely the lamellar start temperatures are similar each other at relatively fast cooling rates. Similar results were also obtained with respect to the transition cooling rate$(70℃s^{-1})$ for the $α→α_2$ ordering reaction as well as to the ordering start temperature(1070℃). The effect of B addition on the continuous cooling transformation behavior of Ti-45.5at.%Al alloy was also quantitatively measured. The addition of small amount of B(0.05at.%) raises the Tα transus temperature by 20℃ and enhances the lamellar formation kinetics. At the same time, the B addition significantly raises the lamellar stability by enlarging the lamellar formation regime toward much faster cooling rates. This is believed to be related to the effect of B to enhance nucleation and growth kinetics of lamellar formation in Ti-45.5at.%Al alloys. The addition of B tends to slightly lower the $α→α_2$ ordering start temperature. The β→α transformation kinetics of CP-Ti during continuous cooling was also measured using the measurement apparatus. Unlikely from the pure Ti case, the massive transformation occurs at medium cooling rates, about 90℃/s to 600℃/s. Its start temperature is estimated to be about 890℃, which is close to the To temperature. The reason for the appearance of massive transformation in CP-Ti is because CP-Ti contains a significant amount of Fe as an impurity, which leads to the $T_o(β→α)$ vs. composition curve being parallel to the composition axis due to its retrograde solubility. The martensitic transformation starts to occur at cooling rate about 500℃/s, which is much slower compared with that (about 3000℃/s) reported in a pure Ti case. This retardation effect of martensitic transformation is also believed to arise from the presence of significant amount of Fe in CP-Ti, which is one of strong β-stabilizers.

서지기타정보

서지기타정보
청구기호 {DMS 02006
형태사항 iv, 121 p. : 삽도 ; 26 cm
언어 한국어
일반주기 저자명의 영문표기 : Seong-Kon Kim
지도교수의 한글표기 : 박중근
지도교수의 영문표기 : Joong-Keun Park
학위논문 학위논문(박사) - 한국과학기술원 : 재료공학과,
서지주기 참고문헌 수록
주제 연속냉각변태거동
Continuous Cooling Transformation
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