AN INVESTIGATION ON THE CREEP BEHAVIOR OF PURE Mg

Μέγεθος: px

Εμφάνιση ξεκινά από τη σελίδα:

Download "AN INVESTIGATION ON THE CREEP BEHAVIOR OF PURE Mg"

Ἡρόδοτος Μεσσηνέζης
6 χρόνια πριν
Προβολές:

1 Ù Ù 11 Vol. No «11 Ù «ACTA METALLURGICA SINICA Nov. 008 pp Mg ²» ¼ (Đ Ý Ê ß Ï Ö Đ ÑÛ Ö, 11189) ( ß ³ ¼, 111) ¾ ß Â Mg Ø 75 00, 15 0 MPa ĐÈ Þ: Ò ĐÈ, Ú Ø ÈÈ, ÅÕ; Ó Ø ¹, È Æ, ÈÏ; ¹ Ê ¹ È, È ¼Ò.» Ú ½, Ú Â Mg Ø ÅÕ Ê, Ê n ¹.3.9, Å± Ê, n >7; kj/mol.» Ê Ã ± Å Ã, Â Mg Ü Î Æ ÎÆ Í, Î ÆÃ ÎÆÄÖ. Â Mg,, Î Æ, ÎÆ TG111.8, TG16. ¹º ± A ¹ (008) AN INVESTIGATION ON THE CREEP BEHAVIOR OF PURE Mg YAN Jingli, SUN Yangshan, XUE Feng Jiangsu Key Laboratory for Advanced Metallic Materials, Southeast University, Nanjing TAO Weijian Nanjing Welbow Metals Co.,Ltd., Nanjing 111 Correspondent: SUN Yangshan, professor, Tel: (05) , yssun@seu.edu.cn Supported by Natural Science Foundation of Jiangsu Province (No.BK0008) and the Foundation for Excellent Doctoral Dissertation of Southeast University Manuscript received , in revised form ABSTRACT The creep behaviors of pure Mg in different states at the temperature range of under the stress range of 15 0 MPa were studied. The results indicate that the grain size has remarkable effect on the creep behavior. The as cast Mg with coarse column grains has low creep rate. However, the creep rate increases significantly as the grains become fine equiaxed due to dynamic recrystallization after extrusion, and decreases when the grains coarsen after annealing. The stress exponents n lie in a range of.3.9 under low stresses, which is corresponding to dislocation climb mechanism. However, the n values are over 7 under high stresses. The apparent activation energies range from 76.0 to 89. kj/mol. According to the stress exponents and the activation energies as well as the microstructure analysis during creep, the creep are affected by dislocation climb, grain boundary sliding and twinning, among which the former two mechanisms play dominant role. KEY WORDS pure Mg, creep, dislocation climb, grain boundary sliding ÖÆ ÔÙ Å Ç Ð º. ½µ Ä ² Û ÓÖÁ Þ Ö ÞÅ * Å Þ BK0008 Ã Þ Ø³ Þ Ù Û ³ : , Û ³ : ÊÞ : ²Å,, 1981 Í, ³ Í Ë µ ÜºÖÁÓ Ü, Þ À Ó ¾ÃÍÎ ²³. «, ÖÆ Ö «, ², Ä Ö É, «² Ý, ÖÆ À. Đ², ¼ßË Ö Æ ¹ Ü ¼Î Í Ý [1 ]. Ö Ô ÖÆ ² Ö Â. ¼º ß ² Ö Æ ÑÖ

$u 11 Æ%Lm : I Mg ie p8, 1355 :G >rn 7KV\Uk., & 6hV g G k S _ Li^, qg ed k. gj k< C, ) g W * J 5 Y C - L aq k s ) C. 9 G 5 <E. <, O Q, -R: a h f r k ), 6 X p r N C& > k L. Q k G E l?$

2 u 11 Æ%Lm : I Mg ie p8, 1355 :G >rn 7KV\Uk., & 6hV g G k S _ Li^, qg ed k. gj k< C, ) g W * J 5 Y C - L aq k s ) C. 9 G 5 <E. <, O Q, -R: a h f r k ), 6 X p r N C& > k L. Q k G E l? d G E k 5 <edz q ) C -K Mg C ( T, T tj, CJlQZ) )$> yl S! Q k 9C x) k G E, " E G f 1 > S Xy G q9 qnjk q. : M k Q< d k, & N G E i 5 < Z K Mg k! 6 9uÆ` (a=0.31 nm, c= Yk L, E* VK Mg CN> ykg q9l 0.51 nm), s> r r. K Mg ^! k ) S a G e J. ).8.9 MPa,! k( L O r, N) 1 '1 [! 6. Y. <, C jr N G q9 k 0! kk Mg w } % # ;G l } 9 ) f,!ok Mg 7f. a)oivk Mg kg ed, Y /, K >99.90%, N GB k /= J N 5 kxj rn G q9 k, 9 ~. p } p C 315 t & } e Q q, Y (w }) > 7Æjm >rn CJlQ! _!. ~ 9 360, p }%> ~ 9 350, p } 9 9 # 9`,.K Mg kg q9k -&). 1, p } S k u S I:.. ` H J C CO " i ) k f\ C Ql v 80 &, * V O, & : q,. ` > 9 500, ` y $ 9 1 L 3 h, a h V1 Y< { y k 5 d. Shi L Northwood ))$!Q ku.!.g ku 0!Bw!~ Jones o Vagarali L Langdon C -K Mg kg (GB/T ) ~ko LBU (!9 100 mm, `, hf<w pg k?ded; Roberts C [+ 10 mm). G C RD 3 m&>g eq -i({v! W CG v Æ k!; Milic ka q, >?dc ±1 k 7. T5 Z0!>{T o G 9 d xqm< Wk) = ( Æ > m< W 5* (OM) LMyz* (SEM) <, G E k5< O d x J } x W M k W l y< W Y d k 6 Y<C JEOL JEM000EX m(sz* (TEM) } x< W W > = pg f? ded. $`, Q q. ) k - \ p V O }G q9 k - C, '1 O>S{k, >! Power Law (w_ ) s + 1a 9K Mg kw Z. %+i= 9F, K [5 7] m [8] [9] [10] [11] [1] + J js Y (a) as cast (b) as extruded 1 Mg Fig.1 Microstructures of pure Mg (c) annealed for 1 h after extrusion (d) annealed for 3 h after extrusion m

3 1356 Þ Ü Ù Mg Û ±É Ø, Ø 1 mm, µ, µm Ý. ÔÐË, Ù ½ Î, Ì Ç ÓÓ, É Í 30 0 µm, Á 1b. 1c Ä d ÔÐË Ã Mg 1 Ä 3 h º ÀÂË., º ÀÂË, Ç ÓÓ µµ, É Í 100 Ä 00 µm «. ÎÃ Mg Û Ù 15, 0 0 MPa. Ç, «Ö ËÉ, Ò, «Ö ÚÇ Ý. Ë ÀÜ, ÍÕ ÀÜ, Ú 1 Æ Ú Ý «ÍÀ, Ú Æ Ú ÝÅÕ, Ç Â Ú 3 Æ. ε s Æ. Ã Mg Û Ù 75 00, 15 0 MPa 1. Ç ¹ßÌØ, Ã Mg Ö Ç, 150, 0 MPa É, s 1. Ä/ Ë À Ü, À. µ É Ã Mg 150, 0 MPa Á 3a, 3b ( )., Ú 1 Æ Ñ É, ²Õ ½ºÈ, «Â Æ. ² Creep strain s, % Creep strain s, % (a) 0 MPa 5 MPa 30 MPa 35 MPa 0 MPa Time, h (b) 90 min 15 min Time, min Ú Â Mg 15, 0 0 MPa Fig. Creep curves of as cast pure Mg specimen at 15 under the stress range of 0 0 MPa (a) and 0 MPa (b) 3a : Û Ã Mg Ù ½µÅÖ ( s 1 ); 3 h º ÀÂ Ù µ ( s 1 ); «1 h º ÀÂ Ù É s 1, ²Î 0%; Ô Ð Ù s 1, º Û Ù 3. Î Î, Û Î½µ 3 µýñ Æ ( b) 90 min( ) Ä 15 min( Ë ) Ë ÕÎ ¾, Á. Ú 1 Æ, Üº ÀÜ, µ É 1 Ü Ä Mg Ú Å, 15 0 MPa Ð À Æ Table 1 Steady state creep rates of the as cast pure Mg at the temperature range of under the stress range of 15 0 MPa (10 8 s 1 ) Temperature Stress, MPa Creep strain s, % Creep rate s, 10-1 s (a) 10 As-cast. s,10-8 s -1 As-extruded 8 Annealed for 1 h 15.8 Annealed for 3 h Time, h 50 (b) Time, h 3 ß ÈÂ Mg 150, 0 MPa Fig.3 Creep curves (a) and creep rate curves (b) of the pure Mg treated at different conditions

Ù 11 Æ±ÄÑ : Á Mg Ô Đ 1357 3 µ 5 Â Mg Ú Ø 15, 0 MPa Ê Fig.

$image showing the fracture morphology, ÐÄÆ ε s ½ Ë Å É Power Law À [1] : ε s = Aσ n exp( Q app /(RT)) (1) Â Mg 15, 0 MPa È TEM È Fig.$ stage, sub grains formed. Â Æ Ë, Ü Ïµ À ÎÜº ; Ü, ¾¾, Ï Ó Ï ( a ³ ), ² ÙÚ ÕÓ, ÒÆ Î. Üº Ä Ë Æ «Ö. Õ, Î Æ Ë, Ù Ó Î Í, Á b. Ã Mg Û Ù 15, 0 MPa Ë Á 5. Ç 5a, ºÃ½ À Ó, ² Ã;, É ÎßÌ.

stage, sub grains formed. Â Æ Ë, Ü Ïµ À ÎÜº ; Ü, ¾¾, Ï Ó Ï ( a ³ ), ² ÙÚ ÕÓ, ÒÆ Î. Üº Ä Ë Æ «Ö. Õ, Î Æ Ë, Ù Ó Î Í, Á b. Ã Mg Û Ù 15, 0 MPa Ë Á 5. Ç 5a, ºÃ½ À Ó, ² Ã;, É ÎßÌ.

4 Ù 11 Æ±ÄÑ : Á Mg Ô Đ µ 5 Â Mg Ú Ø 15, 0 MPa Ê Fig.5 Microstructures of the as cast pure Mg specimen after creep at 15 and 0 MPa (a) optical photograph showing the wedge shaped crack at triple joint grain boundaries (b) SEM image showing the fracture morphology, ÐÄÆ ε s ½ Ë Å É Power Law À [1] : ε s = Aσ n exp( Q app /(RT)) (1) Â Mg 15, 0 MPa È TEM È Fig. TEM photographs of the as cast pure Mg during steady state creep at 15 and 0 MPa (a) initial stage, dislocation cells (sub boundaries) formed, as shown by arrows (b) final stage, sub grains formed. Â Æ Ë, Ü Ïµ À ÎÜº ; Ü, ¾¾, Ï Ó Ï ( a ³ ), ² ÙÚ ÕÓ, ÒÆ Î. Üº Ä Ë Æ «Ö. Õ, Î Æ Ë, Ù Ó Î Í, Á b. Ã Mg Û Ù 15, 0 MPa Ë Á 5. Ç 5a, ºÃ½ À Ó, ² Ã;, É ÎßÌ. 5b Î Ë ÓÓ., À Î., A Ôº, σ Ô Ü Ë, n Ô Ë, R Ô, Q app Ô, T Ô Ëß. (1) Ì ln ε s = lna + nlnσ Q app /(RT) () ¼ (), Ë n É, ln ε s ½ lnσ» ; «Q app ËÉ, ln ε s ½ 1/T». ¼ Ë n Ä Q app Õ. 6 Ô ¼ Û Ù» ½ Ë ( 6a) Ä ( 6b) Ý. Ç Ë n Ä Å. ¹ [13,1], n=3, ÏÂ ( Ï»Þ ) ; n= 6, Ï ; n >7, Ô (1). Ç, Q app 135 kj/mol (Mg Ä ), Ý Mg Ä ; Q app 80 kj/mol (Mg Ä ), Ý Ä. «Ö ËÉ, Ù Ë Àº.3.9,

5 1358 Þ Ü Ù Æ Five Power Law [15], ÔÝ Ï ; «² Ë, Ë º 7. «, Ç ÉÀ, kj/mol, ºÃ Mg Ä (80 kj/mol), ÔÝ Ä., º Ð ( fcc, bcc Ä hcp Ó) À, Ï ½ Ä [15]. «½ Mg ln ( s, s -1 ). ln( s, s -1 ) (a) 100 o C 15 o C 150 o C 175 o C.7.3 n= ln (, MPa) (b) 76. Q app =86.7 kj/mol MPa 0 MPa 5 MPa 30 MPa 35 MPa 0 MPa /T, 10-3 K -1 6 Ê Fig.6 Stress σ (a) and temperature T (b) dependences of steady state creep rate ε s 3.0 Ä, ß «Ö É (<0.5 T m ), Ä Ô Õ. Đ², ÕÌ µ ¹ Power Law Q app ½ Ð Ä [15]. Î [15 17] Î ÅÐÂ ( Mg), Óº Ä. Ô, ÀÅµ Power Law Î, ½ Ä µ½ Æ, ÇÅ º Ä, «º Ä Ï Ä [18 0]. Ì½. ÑÉ, µ ºÃ Mg Õ ¹, µ ßËÅ Îµ, Æ º ÐÅ µ. Î µî [8 10,1,1,] Ã Mg. Ç, µ Ë¼ µ, ÅÌ «, Ô Ë À , º Ä, ¹ËØ ¹ º Ý Ï. Æ µ Î Ü, É, Ï Ò. ØÉ, Ô µý Ë É ÓÔ Å «. Ð Æ ÆÎ Ï ( Ï Ï Ó) (Ï ± Ä) Ì ÎÓ µ Î, Langdon [3] É : ε s = ε g + ε gbs + ε diff(l) + ε diff(gb) + ε twin + (3), ε g Ï, ε gbs Ï, ε diff(l) Ä ε diff(gb) ÄÄ Ä, ε twin Î. ÔÉ Ï»Ä Mg À Ð Table Creep mechanisms of pure Mg reported in the previous investigations Temperature, Stress σ, MPa (Strain rate, s 1 ) n Q app, kj/mol Mechanism Ref [8] ( 10 6 ) [9] ( 10 6 ) [9] [10] (>37) 77 > /σ [10] (>37) 77 < [10] < /σ, [1] > σ 5 [1] [1] [1] [] Note: 1 dislocation climb, cross slip, 3 Nabarro Herring diffusion, slip motion of dislocations on pyramidal slip system limited by nucleation of kink motion, 5 nonconservative motion of jogs on screw dislocations gliding in basal plane

6 Ù 11 Æ±ÄÑ : Á Mg Ô Đ 1359, Ô ÉÐ. º Û À, É²Ü Ù TEM Ä, Ï Ò., ËÙ Ì ¾ Î Ó Ì ( 5a), «Ó Ô± Ï, Á 7, ß Ï Å. Langdon [3,] ¹ ß, Ï Ò, «É ß, º ÎÀ. Bell Ä Langdon [5] ¹Î Mg 0.78Al Æ Ï, É 357 µm Ù 00, 0.7 MPa É Ï ÍÅ Í Æ 6%. Æ¼, µ Ù ß, É (ÔÐ Äº 1 h Ù ),. Á Ô½ ± Ï, Ô ÉÇ, ÀÅ, Ì ¹ÁØ «Ï, ² Ö, «É Í ß «Ö É. Ì ß Ì ÔÊ Î Ï, «Î Ï, Ò Ï ½µÒ. ±º Ä ² Ö ËÉÆ Î [15], É, (3) Ä ( ε diff(l) Ä ε diff(gb) ) Í µ. Æ¼, ËÙ Ì ¾ Î, ß Î ÃÖ Å. Ô Æº É Î º Îµ. Æ, É, Ý Ï Ï Ä Î, Ò ε s = ε g + ε gbs + ε twin () Ï Ä Ï Å Ø. «, Ù Ô, () Ö ßÎ, µ Í ß ½ Ë Ð É Ó «Å., Íµ ¹ º Å² ¾, µ¹å º Ù Ã. 7 ÎÆ Ò Fig.7 Schematic of cuneiform crack caused by grain sliding (1) É Õ µ Ö. Ó É, Û ÉÉ, «Ö; ÔÐËÆÎÎ ÉÇ, É ; º Ë±º É, É ½Ó. () Û Ã Mg Ù «Ö Ë, Ë n À º.3.9, «² Ë, n >7; kj/mol. ¼ Ý µ Ë ßÂÐ, Ë, Ý Ï ; «, Ô Ä. Ðµ Ð ßÎ ÝÂÐ º Ö. ÆÌ Ä, Ã Mg Ý Ï Ï Ð Î, Ï Ä Ï Åµ Ø. ¹º [1] Luo A A. Int Mater Rev, 00; 9: 13 [] Wang Q D, Zeng X Q, Lü Y Z, Ding W J. Mater Rev, 000; 1(3): 1 (¾, Á, Í,. ¹, 000; 1(3): 1) [3] Wang X Q, Li Q A, Zhang X Y. Light Metals, 007; 6: 5 (¾ ³, Ã, ÆÐ., 007; 6: 5) [] Zhang J, Pan F S, Li Z S. Foundry, 00; 53: 770 (Æ µ, Í, Ã. Ú, 00; 53: 770) [5] Mordike B L. Mater Sci Eng, 00; A3: 103 [6] Pekguleryuz M O, Kaya A A. Adv Eng Mater, 003; 1: 866 [7] Zhang X M, Peng Z K, Chen J M, Deng Y L. Chin J Nonferr Metals, 00; 1: 13 (Æ Þ, Đ,, Ô. Æ Þ, 00; 1: 13) [8] Shi L, Northwood D O. Acta Metall Mater, 199; : 871 [9] Jones R B, Harris J E. Joint Int Conf Creep, Part 3A, London: The Institution of Mechanical Engineers, 1963: 1 [10] Vagarali S S, Langdon T G. Acta Metall, 1981; 9: 1969 [11] Roberts S. Trans Am Inst Min Metall Eng, 1953; 197: 73 [1] Milička K, Čadek J, Ryš P. Acta Metall, 1970; 18: 1071 [13] Kim W J, Chung S W, Chung C S, Kum D. Acta Mater, 001; 9: 3337 [1] Chung S W, Watanabe H, Kim W J, Higashi K. Mater Trans JIM, 00; 5: 166 [15] Kassner M E, Pérez Prado M T. Fundamentals of Creep in Metals and Alloys. Oxford: Elsevier Ltd., 00: 1 [16] Sherby O D, Burke P M. Prog Mater Sci, 1968; 13: 33 [17] Sherby O D, Weertman J. Acta Metall, 1979; 7: 387 [18] Poirier J P. Acta Metall, 1978; 6: 69 [19] Nabarro F R N. Mater Sci Eng, 00; A : 659 [0] Nabarro F R N. Acta Mater, 006; 5: 63 [1] Tegart W J. Acta Metall, 1961; 9: 61 [] Northwood D O, Daly K E, Smith I O. Mater Sci Eng, 1985; 7: 51 [3] Langdon T G. Philos Mag, 1970; (178): 689 [] Langdon T G. J Mater Sci, 006; 1: 597 [5] Bell R L, Langdon T G. J Mater Sci, 1967; : 313

Σχετικά έγγραφα

RELATIONSHIP BETWEEN MECHANICAL PROPERTIES AND LAMELLAR ORIENTATION OF PST CRYSTALS IN Ti 45Al 8Nb ALLOY

RELATIONSHIP BETWEEN MECHANICAL PROPERTIES AND LAMELLAR ORIENTATION OF PST CRYSTALS IN Ti 45Al 8Nb ALLOY 49 11 Vol.49 No.11 2013 È 11 Ç 1457 1461 ² ACTA METALLURGICA SINICA Nov. 2013 pp.1457 1461 Ti 45Al 8Nb ± PST ² ¾ Á ¼ Í Æ Ç È Ì Ï Ç É (À Å ³ Í Å ÑĐ, À 210094) Â ± ³ÛØ ÉØ Ø À Ò Ti 45Al 8Nb (À µ, %) ºÔÙ Ýº½