10.063~070(B04_윤성식).fm

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1 J. of Advanced Engineering and Technology Vol. 1, No. 1 (2008) pp Mg-3%Al-1%Zn w ƒœ» y Á x*á **Á Á w œw *w s l I ûer ** t Effect of Thermomechanical Treatment on Microstructure and Mechanical Properties in a Mg-3%Al-1%Zn Alloy Seong Sik Yoon, Moo Hyon Cho*, Woo Suk Jo**, Jo Won Kang, and Woo Yang Jang Dept. of Metallugical Engineering, Chosun University, Gwangju, , Korea *Dept. of Applied Advanced Materials, Seongnam polytechnic College, Seongnam-City, , Korea **AShinpoong Industry CO.,LTD. (Received : Sep. 01, 2008, Revised : Sep. 16, 2008, Accepted : Sep. 22, 2008) Abstract : The effect of thermomechanical treatment conditions on the microstructure, recrystallization behavior and tensile properties in a Mg-3%Al-1%Zn alloy has been studied. Recrystallization temperature of the sheet hotrolled is risen with increasing hot-rolling temperature due to lack of lattice defects such as deformation twins and dislocations. Comparing tensile strain of the sheets which is hot-rolled at different temperature with annealing temperature, the largest elongation is obtained in the sheet hot-rolled at 230 o C and then annealed at 200 o C and/or the sheet hot-rolled at 180 o C and then annealed at 300 o C. With increasing annealing temperature of the hot-rolled sheet, the size of dimples on the fracture surface is decreased and is uniformed throughout fracture surface, but fracture mode is changed to intergranular fracture by annealing above 400 o C. Keywards : Mg alloy, thermomechanical treatment, recrystallization, mechanical property 1. ƒ 1.74 g/cm 3 Mg ƒ ƒ w q sw š», m»» w t v [1]. ù Mg Mg w w w w y ù w ƒ š ƒ hcp» ƒœ š [2]. t w» w e q œ š ù w š z œ v w» ƒ. wr Mg w 200 o C x ƒ w» e q œ w t œ w» w Mg w q l v x w q, p ful { m»» f Corresponding Author Tel : wyjang@chosun.ac.kr wš w ƒ š [3]. Mg w v xœ x x, x x œ Mg w, j» w w w j w. v x w š Mg w t w» w Mg w q, j» w w» y y k. w Mg w q w yw x ƒ f w» w ƒ j» w v w [4,5]. ƒœ Mg w Mg-3%Al-1%Zn w q ƒœ, w w» w y, y w Mg-3%Al-1%Zn w x e w ³ wš w. 63

2 64 Á xá Á Á Tghxq7tqyuigxi y u u rgsgxx Al Zn Mn Si Fe Cr Ni Be Mg Bal. 2. x 2.1. r Mgw q POSCO q (t = 3 mm) yw Table Φ 127 mm L 250 mm»( w ; 25 ton) w r ƒƒ 130~ 320 o C 20 ƒ w z w Ì w ̃ 1.6 ~ 1.8 mm q w z w» w Ar» w 150 ~ 400 o C ƒƒ 30 w. q t y w» w q y w z œþw j» d w» w w j»(10 10 mm) r qw SiC w z ù (0.05 µm) w w. r vj (0.82 g) + (2 ml) + k (14 ml) + (2 ml) yw w z Ÿwx x w w. j» s y»(image-pro) w d w x y w» w f x» w d w. xw 1 kg, 15 w ƒ r 3z d w s³ w. w - x š w» w x» xw. xr fq w ASTM sub-size r(t = 25 mm) w 1 mm/min xw - x š w. q q y FESEM w. 3. š 3.1. y Figure 1 8m/min š wš pass 10 ~17% Ì 130, 180, o C 5z w q ùkü. ƒ 130 o C Figure 1 (a) w w x ü x [6] š ù. ù ƒ 180 o C Figure 1 (b) x w x ƒ ù 3 µm w w w. wr ƒ 230 o C Figure 1 (c) 4~5µm j» w š w ü x / x ƒ ù ƒ 320 o C 230 o C w w ùkû y xk ƒœ w w» ë w w, w, ƒœ w w [7]. Figure 1 r 150 ~ 400 o C ƒƒ 30 w w Figure o C w q 150 o C 30 min w w x sww x û. ù 200 o C 30 min w x û ü x w. ƒ 250 o C 30 min w s³ j»ƒ 3 µm w ù x w. 300 o C 30min 350 o C 30 min x p 350 o C 30min û. 180 o C w q 150 o C 30 min 200 o C 30 min x û ù 250 o C 30 min œw» 1«1y (2008)

3 Mg-3%Al-1%Zn w ƒœ» y q I uigxgui s g t rt xxqp tqq u tt xxu s qy q g q )g! Q 7h& Q 7i! Q 7g pp! Q o C 30 min. ù 350 o C 30 min w w ùkþ. wr 230 o C w q ƒ 150 o C 30 min 200 o C 30min û x ù. ƒ 250 o C 30min w r ù s³ j» 5~6µm ƒ û r f x ƒà ùkû. w 320 o C w q w x w ü x. ƒ 150 o C 30min 200 o C 30min û x ù. ƒ 250 o C 30 min 300 o C 30 min û x ù. w j» x j», x, x, w, j», x z r Ì w. w ü w œ š w ü sw x j w. y yw» w œ ù» w x w jš w š ƒ y yw» w w x ƒ ƒ w [8,9]. Figure 2 ƒ o C x j»ƒ»» w š w w» w w j» w. û x ƒw w ƒ ƒw» w š f j» w. ƒ û, x ƒ ƒw w j»ƒ wš w w. 3.3.» 1) ƒ q ƒƒ 150 ~ 400 o C w r f y Figure 3 J. of Adv. Eng. and Tech., Vol. 1, No. 1 (2008)

4 66 Á xá Á q Gui i gxitg sq r tq tqq t xxqpg p tqg qgxqpg ˆg u qy q g q. 130 o C w f HV = 84.8 ù ƒ w f ww w ùkþ 320 o C f HV = 76.3 w. w y x, ü w». w w ƒ û x f š ƒ j» ùkù ƒ x š p x ù û ùkù. wr y r ƒ ƒw f ww. 130 o C w 150 ~ 400 o C w f ƒ w w w ùkþ. s 200 o C ƒ f w x z û». 180 o C 230 o C w r w f wwù w ùkû. 180 o C q f ww 200 o C 230 o C q f ww 250 o C. w w q ƒ x w ƒ w» w š û ù» [7,10]. wr 320 o C w q y w ùkû. yƒ ƒœ w w w x y w». 2) Figure 1 2 r xw - x š w Figure 4. ƒ 180 o C r k w 36.5 kgf/mm 2, 6.1%. ù q ƒƒ 200, o C w w 27.3, kgf/mm 2 w 9.5, % ƒw. 230 o C q k w ƒƒ 34.3 kgf/mm % ù ƒ w w wš ƒw. ƒ 200, o C ƒw w ƒƒ 23.2, kgf/mm 2 w 18.2, % ùkþ. w ƒ 320 o C r k w ƒƒ 38.2 kgf/mm % ùkþ ù 200, o C w w ƒƒ 27.2, kgf/mm 2 w œw» 1«1y (2008)

5 Mg-3%Al-1%Zn w ƒœ» y q! 7tg squ Vuiwq tg p q ˆgx q r tq tqq t xxqpg g! Q 7h& Q 7i! Q 7g pp! Q 7 u t g qgxu s qy q g q T 4 qi gxxu g u xuyu qy q g q ƒƒ 16.8, % ùkþ. w w,, j», ü w w w w. x Mg-3%Al-1%Znw hcp x r w sww w» y z z, e x j» w. Figure 4 w y x j» š û x w x» w ƒwš w. wr w y ƒ ƒ w x r [7, 10, 11]. w œ y y j w w x ùkù. ƒ r w w Figure 4 w x w. ƒƒ r w 200 o C w r p w 230 o C w r ƒ j ùkû 300 o C 180 o C w r ƒ j ùkû x w w w» w. wr r ƒ 400 o C w w ww w w w». Figure 5 Figure o C w ƒ ƒ w r q x w ùkü. 180 o C w z 200, o C w w r q ùkü Figure 5 k q p j ƒ w v w ù x j ùkù. ƒ w v j» w š q w ³ w x û ù 400 o C J. of Adv. Eng. and Tech., Vol. 1, No. 1 (2008)

6 68 Á xá Á q"s q gu i ˆq r tq tqq t xxqpg pg qgxqp)g& Q 7h! Q 7g pi! Q q#@ gi s g t t u s q uxqr gi q rgiq rgs!5x` gxx tqq t xxqpg & Q 7 u tg qgxu s qy q g q )gg xxqph Q 7i! Q 7g pp" Q 7 w w q. w 320 o C w r k x q ù kþ. ù o C w ù w r w v š œw» 1«1y (2008)

7 Mg-3%Al-1%Zn w ƒœ» y q$@ gi s g t t u s q uxqr gi q rgiq rgs!5x` gxx tqq t xxqpg! Q 7 u tg qgxu s qy q g q )gg xxqph Q 7i! Q 7g pp" Q 7 s 300 o C q p ùküš. ù 400 o C w w q û. 4. Mg-3%Al-1%Zn w q ƒœ w w» w y, y w. 1. w w ƒ û x x w w ƒw ù w w ùkþ. 2. w x ùkû. ƒ û x, x ƒw w ww j» wù ƒ w š w w» w w w. 3. ƒƒ r w w w w 200 o C 230 o C w r ƒ j ùkû 300 o C 180 o C w r ƒ j ùkû. 4. q w q ƒ w v j» w š q ³ w x û ù 400 o C w q. š x (1) wk«, y,, y,, 17(6), 41 (2004). (2) Y. Kojima, T. Aizawa, S. Kamado and K. Higashi, Mater. Sci. Forum, 3, (2003). (3),,,, ½,, ¼,, q x x, w 2 (2008). (4) Shoichiro, Y., Hisashi, N., Hirokuni, Y. and Manabe, K., J. Mater. Processing Technol., 142(3), 609 (2003). (5) Chen, F. K., Huang, T. B. and C.K. Chang, Int l. J. Machine Tools Manufacture, 43(15), 1553 (2003). J. of Adv. Eng. and Tech., Vol. 1, No. 1 (2008)

8 70 Á xá Á Á (6) Su, C. W., Lu L. and Lai, M.O., Philosophical Magazine, 88(2), 181 (2008). (7) Humphreys, F.J. and Matherly, M., Recrystallization and Related Annealing Phenomena, Pergamon, New York, 178 (1995). (8) Baker, I., Intermetallics 8, 1183 (2000). (9) Doherty, R. D., Huges, D.A. and Humphreys, F. J., Mater. Sci. Eng., A238, 238 (1997). (10) Beer, A. G. and Barnett, M. R. ibid., A485, 318 (2008). (11) Chang, J. C., Wang, J. Y., O, C. M. and Lee, S., Mater. Processing Tech., 140, 588 (2003). œw» 1«1y (2008)