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1 [ ] œwz, 21«6y(2008) J. of the Korean Society for Heat Treatment, Vol. 21, No. 6, (2008) pp. 300~306 š y w p x*, **Á **Áy y* * ** w œ w œw, w» gœ Solid State Diffusion Brazing of the Aluminum Alloy Castings According to the Heat Treatment Conditions J. H. Sun*, **, S. Y. Shin**, J. W. Hong* *Department of Advanced Materials Engineering, Chungbuk National University, 410, Sungbong-Ro, Heungduk-Gu, Cheongju , Korea **Department of Eco Materials & Processing, Korea Institute of Industrial Technology 7-47, Dongdo-Dong, Yeonsu-Gu, Incheon, , Korea Abstract Solid state diffusion brazing of aluminum castingsg (AC4C) and wrought alloysg (Al6061) was conducted in order to improve thermal conductivity and temperature uniformity of the aluminum heater which was generally fabricated by casting method. Tensile strength and thermal conductivity are raised with increasing brazing temperature, obtaining MPa and 206 W/m ½ K at 540 o C 5hrs brazing conditions, respectively. The diffusion brazed heater, shows maximum temperature difference of 4 o C, exhibits a enhanced temperature uniformity compared with the cast heater having the maximum temperature difference of 11 o C. (Received October 17, 2008; Revised October 23, 2008; Accepted October 31, 2008) Key words: Solid state diffusion brazing, Aluminum castings, Heat treatment, Metal heater, Semiconductor 1. CVD/PVD œ r j p w ƒ j» w k l» ü ƒ l(sheath heater) ü w xk. l 400 o C w œ l œ w, w w. l w š j wš» œ w w x lƒ š [1]. ù x l» w ƒ w w ³ ƒ x l w v w. rƒ l ww l ³» w w. w w, y w š. œ w y š ù, w š ü w» k û û. l w y w w» v w [2, 3]. ù ƒ w w ƒ û wœ ƒ w e š p ù. û w ƒ w š y w»» jhhong@cbnu.ac.kr

2 š y w p 301 Table 1. Chemical compositions of the base metals Chemical composition (wt%) Alloy Al Cu Si Mg Zn Fe Mn Ni Ti Pb Sn Cr AC4C Bal. < < 0.35 < 0.55 < 0.35 < 0.10 < 0.20 < 0.10 < 0.05 < 0.10 Al 6061 Bal < 0.25 < 0.7 < 0.15 < 0.15 Table 2. Major properties of the base metals Tensile Strength (MPa) Al6061 AC4C Alloy Al-Mg-Si system (Wrought alloy) Al-Si-Mg system (Casting alloy) M.P. ( o C) 582~ ~610 š. w y w p w ù š, x» ƒ š w [4-6]. x l w AC4C w Al 6061 w š y w w w p sƒw. 2. x 2.1 w Table 1 yw Al AC4C Al 6061w w w r j» l w φ200 mm t15 mm w. w Al AC4C Al 6061 w p Table 2 ùkü. 2.2 w š y w w 5 C o k z 500, C ww z o þ g. w ƒƒ 2 5 g w 5MPa š w. w 100 Tonf š œ w v w w 5 10 Torr š 6 œ» w. O ~ 176 T ~ 284 Hardness O (H B ) T Thermal Conductivity (W/mÁK) Fig. 1. Schematic diagram of the tensile test specimen. 2.3 w w y w» w Ÿwx (PHDT-M, Nikon) w r e Keller (20 ml distilled water, 20 ml 32 HCl, 20 ml 65% HNO 3, 5 ml 40% HNO 3 ) w. w X-ray z» (XRD, D8 discover, Bruker) w w y w. 2.4 w d w d w» w Fig. 1 w xr w. x x»(mts 810 series) w 3 mm/min x d w. w w t w y wœ q w w» w y w ƒ [4, 6].

3 302 xá Áy y Fig. 2. Schematic diagram and feature for the thermal conductivity test.»(mhv-2000) w w d w w y y w. 2.5 d w d Fig. 2 e w Al 6061 t w (Static comparative method) w. w qƒ w š ƒ w, d w. K 1 K q = T 1 A 1 = T 2 A 2 L 1 L 2 K = K 2 A 2 L T A 1 L 2 T 1 (1) (2) K 1 t r K 2 d r w yw» w torr œ» w d w 5 š, ùƒ w» w 75 µm w. d w r x s 5 mm, ¼ 5 mm, Ì 8mm w ¼ w w ƒ ew w. 2.6 l ³ 300 mm x l w z Al 6061 w š y ww l ³ d w. d l 200 mm r e k z 10 w r t d w 400 o C ƒ k z, r ƒ e d w r w. 3. š 3.1 w Al AC4C w Al 6061w š y wp w sƒw. (555 o C) w ƒ w š š y w x w e y. Fig. 3 w ùkþ. Al-Si œ y x. ƒ 500 o C w 100 µm w»œ w w y w š ƒ 540 o C ƒw» œ w w x w y w. Fig o C o C 5 w XRD ùkü. 500 o C 5 y Al 2 O 3,» t w y w y w w š w û. 540 o C 5 w Al, Si y Mg 2 Si w y š y. w ƒ w œ ƒ y y y w š y w y y» ƒ š y y ƒ w w j š [5]. š y w y w w y w» w 540 o C 5 w y w.

4 š y w p 303 Fig. 3. Microstructure of the diffusion brazed joint with various temperature and time. Fig. 4. XRD patterns of the joint specimens at 500 o C and 540 o C brazing temperature. 3.2» w w w w yw y w w ƒ w š ƒ ƒw. w d mw» p sƒw. Fig. 5 d ùkü. 2, ƒ 500 o C w ƒ 13.8 MPa û ù ƒ 540 ƒw MPa š w. ù d 10.3% û w q w ƒ w û. 2 w w yy x». 5, 540 o C MPa 23.2% Al AC4C q w w ƒ š w x w y w. w Fig. 6 w d y w ƒ ƒwš ¼ w ƒ w y w. 500 o C 2 ƒ H B =63 Fig. 4 XRD y w w w y» w q.

5 304 xá Áy y Fig. 6. Hardness in the joint area with various temperature and dwell time. Fig. 5. Mechanical strength with various brazing temperature and time; (a) tensile strength and (b) elongation. 3.3 d w Al AC4Cw W/mÁK Al 6061w W/mÁK. w mw l w j. w r d w Al 6061w w p y w. Fig. 7 w r d ùkü. 2, 500 o C W/m K ƒ 520 o C ƒw 179 W/mÁK Fig. 7. Thermal conductivity of the joint specimen brazed with various temperature and dwell time.. w 5 ƒ 500 o C W/mÁK Al 6061w w. w 540 o C W/mÁK Al 6061 w w 110%. ƒ w» w x w w w (Fig. 8). ƒ 500 o C AC4C d 1 mm w»œ y ù, w ƒ 540 o C ƒw ü»œ x w y w. ƒ ƒw w š Áƒ y w

6 š y w p 305 Fig. 8. Macrostructure of the solid state diffusion brazed specimen. Fig. 9. Temperature uniformity of the fabricated aluminum heater; (a) cast heater and (b) diffusion brazed heater. ƒ xw»œ jš w ƒ j ƒ. w Al 6061w z yx w ü w s (Phonon) w š w w û ƒ š [7]. w 540 o C» ü š T6 ùkü. 3.4 ³ š y ww l ³ d w» w 300 mm l w z Al 6061 w š y ww. x l š y w ƒƒ l w 400 o C ƒ k z, r ƒ e d w r w Fig. 9 ùkü. l o C~408.6 o C s r

7 306 xá Áy y 11.1 o C d š, w l o C~403.9 o C s r 4 o C d. mw wx l ³ ƒ y w. 4. œ x l ³ w» w Al AC4C w Al 6061 w š y wp w. 1. ƒw w ƒ ƒw 540 o C 5 5MPa 123 MPa 23% ùkü. 2. XRD 520 o C w w w y 540 o C. 540 o C w y w y, w w ƒ w. 3. ƒw Al AC4C / Al 6061 w r ƒw, 540 o C 5 5MPa Al W/ mák. w ü y w,»œ š z» w š q. 4. l ³ d w x l 11.1 o C r wx l 4 o C r, š y w mw w l r ƒ w y w. z» w 2007 w w. š x 1. T. Osawa : Welding Journal, 74(6) (1995) J. T. Niemaann and G. W. Wille : Welding Journal, 57(10) (1978) R. S. Timsit and B. J. Janeway : Mater. Res. Soc. Symp. Proc., 314 (1993) T. Osawa and I. Kawakatsu : Jpn. Inst. Light Metals, 29(3) (1979) Mel M. Schwartz : The Materials Information Society (2003) D. P. Sekulic, P. K. Galenko, M. D. Krivilyov, L. Walker and F. Gao : Int'l. J. of Heat and Mass Transfer, 48 (2005) ª : qxwuqwl k (1991) 477.