MICROSTRUCTURE STABILITY IN A FULLY LAMELLAR HIGH Nb TiAl ALLOY AFTER LONG TERM THERMAL CYCLING

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1 Ö 49 Ö 11 Vol.49 No Ò 11 Ö ACTA METALLURICA SINICA Nov. 013 pp ßÍ Ø Ç Nb TiAl Ë ÚÒ Ö Þ 1) «) 1) 1) 1) 1) Í Ä Ñ Ø ËÈ, ) Ñ Ä, Đ ß½ Â Ã ( cyc) Ì, Ø À (OM) ½ Ú (SEM) ß Ú (TEM) Ç Â ±Û Ã ÔÜ Ð ß. Ç, ß½ Ç ³ÈÔ»Ü (Al Ü ) ²Å ¼Ã, 900 Ã È Al Ü Ç ± Í, 1000 cyc Ã È²Å α ³Ð Í; 1000 Ã È Al Ü Ç Á ½, 500 cyc Ã ÈÉ Â ¾ÐÓ², Û α ³ Í Á cyc Ã È Ö ÀÐÓ² Á, Ö±Û ¹Ð Ô α ³ Á; 1000 Ã È, Ô α ³Ï É {111} Á, α ³Ü ÐÆ ¹½. ÈÏ Nb TiAl, Ã, ß, ³ ÐÃÆ Ê T146. ÕÜ A Õ Ê (013) MICROSTRUCTURE STABILITY IN A FULLY LAMELLAR HIH Nb TiAl ALLOY AFTER LON TERM THERMAL CYCLIN FAN Lu 1), DIN Xianfei ), ZHAN Laiqi 1), HAO uojian 1), LIN Junpin 1) 1) State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing, Beijing ) National Center for Materials Service Safety, University of Science and Technology Beijing, Beijing Correspondent: LIN Junpin, professor, Tel: (010)63319, linjunpin@ustb.edu.cn Supported by National Basic Research Program of China (No.011CB605500), National Natural Science Foundation of China (No ), China Postdoctoral Science Foundation (No.01M50166) and Specialized Research Fund for the Doctoral Program of Higher Education (No ) Manuscript received , in revised form ABSTRACT Microstructure stability in the fully lamellar alloy were investigated by OM, SEM and TEM after long term thermal cycling (500 and 1000 cyc) at 900 and The results showed that Al segregation could not be eliminated completely after the heat treatment. After long term thermal cycling at 900, the discontinuous coarsening was inclined to occur in the Al segregation region in the alloy. And almost no spheroidized precipitates of α were observed even after 1000 thermal cycles. After long term thermal cycling at 1000, the massive grains were generated in the Al segregation region. After 500 thermal cycles, the spherodized α precipitates were produced within grains which were found at colony boundaries. After 1000 thermal cycles, however, the large equiaxed grains containing different orientation of plate shaped precipitates * Ò Ù ÅÇ Ì 011CB605500, Ò¾ À , ÃÈ À 01M50166 ÓÀ ÃÀ Ù Ç ¼µ Ê : , Ê : Ö :, Ö, 1990 Ó, Ã DOI: /SP.J

2 Ö 11 Ò : ÂÏÓÛ Þ¼ Nb TiAl Þ 1417 of the α phase were observed within the lamellar structure or at colony boundaries. After long term thermal cycling at 1000, the plate shaped or particle shaped α, which is coherent with the matrix, precipitates on the {111} plane in the grain interior. KEY WORDS high Nb TiAl alloy, thermal cycling, thermal stability, phase transformation Nb TiAl ÀÅ Õ Đ «Đ Ñ ±ÎÎ Ñ ± Ñ, Æ Ó Đ ÊÝÑ TiAl ÀÅ , Å º Ò ÔÈß ÃÀ³ÑÑÓ [1 3]. ÆÑ, Nb TiAl ÀÅÑ ±Ó³¹, Ä Ã Í, Ë± Ñ Ñ Ó. ÐÍ, È Ä Õ Ý Ñ Å º ÎÑÓÑ Æ [4,5]. ¾ Ñ TiAl ÀÅ Ô Ñ «Đ Ç Ñ Û [6 8], Æ α + Ñ ¾ Ó ß ² [9,10]. Huang Ô [11] Nb TiAl ÀÅ Ã 700 Í Í, Â Ã ², α ¾Ñ 3 ÆÁ. Å Í Nb TiAl ÀÅÑ È ÁÑ [10 14], ÅÀÅ Ä Ñ «Ù ºÈ. «ÀÅ Í Í ÑÈ Å²¹Ñ, ÆÅÐ ºµÝÑ ±ĐÆÛ Ä ¹. ¹ ÀÅ Ë Ä Ó, Æ Ñ ÙÅÅ Ñ, É Æ Ñ, Æ Ñ Ó Æ ² Î [5,15]. Æ ¹ ÀÅÑ ² ß ²ÜÛÜÔ ĐÝ Õ Ñ Í. ÐÍ, È Nb TiAl ÀÅ Ä ÕÝ Å. Å, ÀÅ ÕÝ Ñ ³«. ¾ Ti 45Al 8.5Nb 0.W 0.B 0.0Y (Ð½, %) ÀÅ Ä Í ( cyc), Ó¾ Û (SEM) Û (TEM), ²Ü Đ Ä ÀÅ ÑÒµ, ÐÐ. È Nb TiAl ÀÅ ÝÑÓ µ¹ ², Nb TiAl ÀÅÑÅ Ñ. 1 ÐÄÂ Ó À Å Ñ Î Á Ti 45Al 8.5Nb 0.W 0.B 0.0Y (Ð½, %), Ti 45Al 8.5Nb(W, B, Y). ÀÅ Ô ½ ËÌ (PAM), ºÔ»Î È ÐÀÀ Å. ß ÀÅ 1340 (α ) 1 h, Ì 900 ÎÈ 30 min, º, Õ α / ¾ Ñ ¾ (FL). Ä ÍÉ Ù Û Ë² 1 mm 1 mm 5 mm, ÐÑË SiC Õ 100, É Ú 15 min. Ä Í YHL(1.5 1) Ñ Ð Ä Ì, Í Å º. Ì Å Ó 1 h, º 1 min Ä. ß ¾ÀÅÉ 3, , cyc Ñ Ä Í, 0 cyc(«ä ) Ó. É ÂÓ Ì«Ð, Ñ Ó. ß Ä ÍÅ ÐÓ ºÅ Ï, ÓØ 5 ml HF+10 ml HNO ml H O Ñ, Ó Á (OM) Ä ÍÅ Ð ¾. É, ß²Ü Đ Ä ÍÉ ÑÀÅÉ Ãº, Ä ÎÎ¾ÑÒ µ, Ã Ó , Ó ZEISS SURPA55 Å Û Ñ ¼ Á, JEM 010 Û½ Ä 0, cyc ÉÉ Î. TEM Ó ÙÛ Ø É» (7 V, 30 ), Û Õ Î ÝÌ Ô Ì, Ñ Đ ¾Õ (α +) (+) Å edge on Æº Ñ TEM»Á, ± 30 Å. Ð É.1 Î Ì ÛÓ 1a c Å ¾ ÀÅ Ä ÅÑ OM, BSE TEM. Å, ÀÅ È Ã ¾ Õ (63± 7 nm) Ñ ¾, ¾ Ð. Ti 45Al 8.5Nb(W, B, Y) ÀÅ ¾ È ÉÕ¼Ý (Al Ý ) ³«½Ä, BSE Á Đ, ² ¹ Û Ñ, ¹ 1b Â. EDS SEM, Õ¼Ý Ð Al Õ Nb.. ÔÀÙ ÎÁÛÓ Ý..1 SEM ÆÅ a b Ti 45Al 8.5Nb(W, B, Y) ÀÅ 900, Ä cyc É BSE. Â, Ý 1b Ä ÅÀÅ, Ä É Al Ý Ø, ÀÅ 500 cyc Ä É, µ Al Ý È³ ÀÀ ¾ cyc Ä É, µ Ý È ² Î (DC)», Å (α +) fine (α +) coarse, Æ ¾ÆºÝÀÀ ¾Æº²Ü. É, ÀÅ 1000 cyc Ä É Ð ³«Å Ñ Â.

$T F 1418 m r 49 P{18 l 900 1000 cyc SEM BSE "KX 500 B + Fig. SEM BSE images of alloy after long term thermal cycling at 900 for 500 (a) and 1000 (b) thermal cycles vs6mq-_)a- α ( J, f α (m V J.$ .. TEM Æ ~ 4a C b J H 900, < 500 C 1000 cyc #LYQ (α +) m TEM :[~.,u, 900 : #LYQ Al α + (u< α ( m), Æ α ( O P sæ m N. ( H H O (~ 1c), #LYQ m O s o. LK#LY<B 9 6>mD D Z V, α m + ZM g O m (Y} l.

.. TEM Æ ~ 4a C b J H 900, < 500 C 1000 cyc #LYQ (α +) m TEM :[~.,u, 900 : #LYQ Al α + (u< α ( m), Æ α ( O P sæ m N. ( H H O (~ 1c), #LYQ m O s o. LK#LY<B 9 6>mD D Z V, α m + ZM g O m (Y} l.

3 T F 1418 m r 49 P{18 l cyc SEM BSE "KX 500 B + Fig. SEM BSE images of alloy after long term thermal cycling at 900 for 500 (a) and 1000 (b) thermal cycles vs6mq-_)a- α ( J, f α (m V J. H 1000 cyc #LYQ, $/%oe", $ l e P Ja I ma A, Æ Al)"s : q-_)a- α ( J, xa " Al) Jm: q- α (.^. ~ 3g 1000 cyc #LYQX} d { Jma Al ) 49 a ~,. q~,b$j, f AF\}aA, l) J s!.m:q- α (, &x.m α :q ql a 70 :t (u~ m J)... TEM Æ ~ 4a C b J H 900, < 500 C 1000 cyc #LYQ (α +) m TEM :[~.,u, 900 : #LYQ Al α + (u< α ( m), Æ α ( O P sæ m N. ( H H O (~ 1c), #LYQ m O s o. LK#LY<B 9 6>mD D Z V, α m + ZM g O m (Y} l. ~ 4c J 1000 cyc #LYQ α / m& DD Z V TEM :[, ~ vz 1 C H H e & DD Z V.,u, & DD Z V m O e q "e"awhh,.yhh m1 BSE TEM B + "KX OM, SEM Fig.1 OM (a), SEM BSE (b) and TEM (c) images of the fully lamellar before thermal cycling ~ 3a g H 1000 #LY 500 C 1000 cyc Q BSE 49 ~,. ~ 3a C b H 1000 #LY 500 C 1000 cyc Q Al y P BSE 49 ~,. X ~,b $J, Al y P Ja A, }s (α +), 1?. 43 "X}, " $ 900 #LYQ6>m &DDZV$/. ~ 3c C d H 1000, #LY 500 C 1000 cyc Q#9 e( V m BSE 49 ~,, ~ 3e C f ) a~. X~,b$J, H 500 cyc #LYQ, R P JB 3 A, Al)

4 r 11 =n : 8!JWow z0 Nb TiAl F 7 z= "KXPl BSE 38 }+ SEM BSE images of lamellae in the Al segregation region (a, b) and microstructure changes (c g) in alloy after long term thermal cycling at 1000 m3 Fig (a, c) after 500 thermal cycles (b, d) after 1000 thermal cycles (e) magnified α + in Fig.3c (f) magnified α + in Fig.3d (g) large equiaxed grains containing different orientation of plate shaped precipitates of the α phase after 1000 thermal cycles

$T F r 49 &x; ) Al:?m& DD ZV m α (vz 1 ) e, & DD Z V Mu<1 H H M&DDm_ \ lm Om;.RmHH α / :?m. H 1000 : #LYQ, TEM 43 (α +) 9 m&?$ ,$i, Al)s :q- α ( J, Æ 1000 cyc #LYQ (~ 5b) α ( 500 cyc(~ 5a) se" :a, Æy ` SEM 43 :^. ~ t5 J Jm α :qy amm SAED SX,.9w1Y Æ." [110].

,$i, Al)s :q- α ( J, Æ 1000 cyc #LYQ (~ 5b) α ( 500 cyc(~ 5a) se" :a, Æy ` SEM 43 :^. ~ t5 J Jm α :qy amm SAED SX,.9w1Y Æ." [110].

5, ÆZ M~ 3g 43iq- α ( 140 α α m4 {1l (α +) TEM 9Z} 900 "KXP Fig.

5 T F r 49 &x; ) Al:?m& DD ZV m α (vz 1 ) e, & DD Z V Mu<1 H H M&DDm_ \ lm Om;.RmHH α / :?m. H 1000 : #LYQ, TEM 43 (α +) 9 m&? V, y 900 (, α m + e O " o. ~ 5a C b J Ti 45Al 8.5Nb(W, B,Y) H 1000, < 500 C 1000 cyc #LYQ Al ) J ( m TEM : [.,$i, Al)s :q- α ( J, Æ 1000 cyc #LYQ (~ 5b) α ( 500 cyc(~ 5a) se" :a, Æy ` SEM 43 :^. ~ t5 J Jm α :qy amm SAED SX,.9w1Y Æ." [110].,u, l Jm:q- α (yam q' E {111} //{0001} C h110i //h110i +! Æ.. q- α (R (m {111} ` J, {111} ql 70.5, ÆZ M~ 3g 43iq- α ( 140 α α m4 {1l (α +) TEM 9Z} 900 "KXP Fig.4 TEM images of alloy after long term thermal cycling at 900 (a) after 500 thermal cycles (b) after 1000 thermal cycles (c) discontinuous coarsening of α / after 1000 thermal cycles m5 1 k( I'l "KXP{ 9Z}d SAED RW 1000 TEM Fig.5 TEM images of α plates precipitated in grain of alloy and their SAED patterns (a) after 500 thermal cycles (b) after 1000 thermal cycles

6 Ö 11 Ò : ÂÏÓÛ Þ¼ Nb TiAl Þ 141 Õ 70 ÑÐÐ. ÐµÄÃ Â Õ¹ α, µ ¹ α Â, Ù È /α SAED Ë, µ ¹ α Ý Ñ³ ¾. 3 Å Í, ¾ ÀÅ ²Ü ĐÕÝ, Ä ÍÉ Ñ. Ñ : (1) Å α ¾Ñ ¾ÇĐÑ Ó, Đ, Ä Î,» ; () 900 Ä É Al Ý È ¾ ² Î, 1000 Â ¾ ; (3) 900 Ä É«Å α Ñ Î, 1000 Ð Â Ñ, Æ Ðµ Õ¹ µ ¹Ñ α Â., ² Î Á, Ñ ±Ñ (α ¾ Ñ ¾Ðµ Ñ ) Ñ (² Î Ð α Ñ Â) [10,16 18]. ¹ 1 Â, ÀÅ ¾ È É, ÀÀ ¾Õ, ÀÅ Ñ ¾ÑÑ ÕÛĐÄ Ñ Á, α ¾ Å Ñ Á Û ¾. ÐÍ, Đ Ä, α ¾ÑÑ ³Þ ÆÛĐÄ, Å α Ñ (α ). Æ, ÀÀ ¾Õ, Ñ Ñ ĐÄ, α Ñ» Æ, ÅÙ È ±Ñ Ç ¾È Æ Æ Ñ [5,9] ( 4b). Ü, Í Â, ÀÅ 1000 Ä É Al Ý È ÂÃ ¾Ñ ( 3a b). Ti45Al8Nb» Ïº Â ÀÅ 1000 ĐÄ ÑÐ½, Đ 8%. ÐÍ,» Ä Î Ñ Ó, Ð (α +) ¾Ñ Ø, ÑÑ, Æ Al Ý ÈÔ Â. 900 ÀÅ 1000 cyc Ä É Al Ý È ¾ ² Î» ( b). ² ÎÕ ¼ ¼, Å «ÜÉ Ñ ² Ñ «Ñ [16]. Ð α / Ñ ÎÁ ÕÑÑ Ø, Ø ÑÜ ÕÛÝ ĐÄ Ñ Ñ [17,19]. ÛÜÔ Đ Í Í, Ä ß ± Ñ² Î Ð. ÆÅ Ð, ÕÛ α Ú«ÁÑ²Ü Õ ÃÐ Ñ Ñ, Ã Ñ α / Ñ [5]. Æ ÆÃ ÜÔ Đ ± Đ Í «² Î» [9,10,13]., 1000 ÀÅ Ä É, «Å ¹ 900 ¾ Ñ² Î». Å» Ä Î Ñ Ó, Ð È Â, Æ ÐµÚ Â Ñ α ( 3), α Ñµ ¹, Ñ Õ¹, Ñ Ç Ñ. ÐÐÝ Ñ Ñ Â Å Ñ, 1000 Đ Ä Ñ, α Ñ, Ð Í² ¾ ( ¾² Î), Å ÑÑ (α +). ÆÂ ÑÅÕÛ 1000 Ti Al Ô Ñ ¼, ÎÁ ÕÑÑØ Ñ [18]. 4 (1) ² Î Á, Å ±Ñ, α ¾Ñ ¾Ðµ Ñ ; É Å Ñ, ² Î Ð α Ñ Â () ÀÅ 900 Ä É, Al Ý È ² Î, Ð α / Ñ ÎÁ Õ ÑÑØ (3) 1000 ÀÅ Ñ Æ Ý ĐÄ Ñ, Ä É, Al Ý È Â ¾ cyc Ä É, Ð ÂÑ Á Ðµ Ñ α Â, Æ {111} /{0001} α 110 α / 110 Æº¾. ÕÜ [1] Kim Y W. JOM, 1995; 47: 39 [] Wu X. Intermetallics, 006; 14: 1114 [3] Lin J P, Xu X J, Wang Y L, He S F, Zhang Y, Song X P, Chen L. Intermetallics, 007; 15: 668 [4] Appel F, Brossmann U, Christoph U, Eggert S, Janschek P, Lorenz U, Mülauer J, Oehring M, Paul J D H. Adv Eng Mater, 000; : 699 [5] Zhao W Y, Pei Y L, Zhang D H, Ma Y, ong S K, Xu H B. Intermetallics, 011; 19: 49 [6] Kim Y W. J Mater Sci Technol, 1994; 10: 79 [7] Es Souni M, Bartels A, Wagner R. Mater Sci Eng, 1995; A19 193: 698 [8] Morris M A, Leboeuf M. Mater Sci Eng, 1997: A39 40: 49 [9] Hu D, odfrey A B, Loretto M H. Intermetallics, 1998; 6: 413 [10] Ramanujan R V, Maziasz P J, Liu C T. Acta Mater, 1996; 44: 611 [11] Huang Z W, Voice W, Bowen P. Intermetallics, 000; 8: 417 [1] Cheng T T. Intermetallics, 1999; 7: 995 [13] Huang Z W, Cong T. Intermetallics, 010; 18: 161

7 14 Ì Ö 49 [14] Beschliesser M, Chatterjee A, Lorich A, Knabl W, Kestler H, Dehm, Clemens H. Mater Sci Eng, 00; A39 331: 14 [15] eng H B, He S Y, Lei T Q. Acta Metall Sin, 1996; 3: 51 (²Æ, ÄÞ, Ö. ÎÀ, 1996; 3: 51) [16] Manna I, Pabi S K, ust W. Int Mater Rev, 001; 46: 53 [17] Qin, Wang J, Hao S. Intermetallics, 1999; 7: 1 [18] Wang X P, Zheng Y R. J Mater Eng, 000; (7): 0 ( ¾, µ. Å³, 000; (7): 0) [19] Tang J C, Huang B Y, He Y H, Xie K. Trans Nonferrous Met Soc China, 000; 10: 10 ( : )

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