Ø 48 Ø 10 Vol.48 No.10 2012 10 Ø 1160 1165 ACTA METALLURGICA SINICA Oct. 2012 pp.1160 1165 Ï DP1180 Æ É ¹Ã ³Ê µ Ô 1) Õ 1) ÙÝ 1) Ñß 1,2) ÐÛÚ 1) 1) ÙºÒ Ù» Ù, 100083 2) ÓÞ, 100043 Ü ĐÛÊ Hopkinson É Þ DP1180 ÎÂÜĵ Ý» 0.001 s 1 Ê 500, 1750 s 1 к ÊÐ ÉÂÍĐ, Swift Í ÍĐÖ Ð Á Ï, ± Crussard Jaoul ÅÀ Swift Ö.  : к ÊÐ ÉÂ, É, Ù Ý À À²; Ù Ý À ; ÜÈ Ý À Æ 3.12% Ï 1.28%. ¹ Ý, Ð ² ± Ý Ñ, Í ÆÄ, ËÁÏ 90 nm, «µđí Ò (GNB) É DP1180 Üĵ ¹ Ý ÄÔµ Å ; Ý» 1750 s 1 Ê, È T=103 Ð Æ. Üĵ, ¹ Ý,, Crussard Jaoul, ĐÍ Ò ¾± TG142.41 ÁÅ A Á ± 0412 1961(2012)10 1160 06 BEHAVIOUR AND MECHANISM OF STRAIN HARDEN- ING FOR DUAL PHASE STEEL DP1180 UNDER HIGH STRAIN RATE DEFORMATION DAI Qifeng 1), SONG Renbo 1), FAN Wuyan 1), GUO Zhifei 1,2), GUAN Xiaoxia 1) 1) School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083 2) Shougang Research Institute of Technology, Beijing 100043 Correspondent: SONG Renbo, professor, Tel: (010)82377990, E-mail: songrb@mater.ustb.edu.cn Supported by High Technology Research and Development Program of China (No.2009AA03Z518) and Basic Theory Research Fund of Engineering Research Institute of USTB (No.YJ2010 006) Manuscript received 2012 06 20, in revised form 2012 07 16 ABSTRACT Strain hardening behaviour and mechanism of a cold rolled dual phase steel DP1180 under quasi static tensile condition at a strain rate of 0.001 s 1 by electronic universal testing machine, and dynamic tensile condition at strain rates of 500 and 1750 s 1 by split Hopkinson tensile bar (SHTB) apparatus were systematically studied. According to the modified Swift true strain stress model, the experimental data was regressed by using nonlinear fitting method, and strain hardening exponent in the modified Swift model was calculated by a modified Crussard Jaoul method. The results revealed that there are two stage strain hardening characteristics of DP1180 steel at the strain rate range of 0.001 1750 s 1, the strain hardening ability of the stage I was enhanced with increase of strain rate, while the strain hardening ability of the stage II was weakened, and the transition strain was decreased. The ferrite near the martensite regions formed cell blocks with dislocation structures, with a size of 90 nm, due to the limit of deformation compatibility, * Á ¹ Ôß Ä È 2009AA03Z518 Ê À Ú ß ÙÂ ß Ù È YJ2010 006 Û» : 2012 06 20,» : 2012 07 16 «Ê :, Å, 1986 Æ, Æ DOI: 10.3724/SP.J.1037.2012.00364
Ø 10 Ñ : DP1180 ÛÃ Ü ºÞÚÐ 1161 and the existence of geometrically necessary boundary (GNB) made DP1180 steel not instantly damaged under deformation at high strain rates. In addition, the adiabatic temperature rise of T = 103 made martensite easy to have plastic deformation at a strain rate of 1750 s 1. KEY WORDS dual phase steel, high strain rate, strain hardening, modified Crussard Jaoul analysis, geometrically necessary boundary ÝÅ º Þ Ö»³ Ö» Ó ÝË Æ, Ø ¼¾Ì Ö Å [1 8]. ² Å«Õ Þ 10 3 s 1 ŵ, Á ß ½ Û, º Þ º³ÏÃÝÅ Æ Á Õ Ô Û [9]., ÝÅ Ë» ¼ ÜÒ Å., ÕÇ Ó [10] Ñ Å Ö 600 MPa ºÚÝÅ ¹ Ç, ² ¾ Ë ; Kamp Ó [11] Hollomon Jaffe ÑÓÖ 800 Ë 1000 MPa ÏÃÝÅ Ë Æ Ç; Colla Ó [12] Hollomon, Pickering, Crussard Jaoul Ë Bergstrom 4 Ö Ñ DP600 Ë DP450 ÝÅ ¼. ÝÅ º Þ ¼ Å, ʳ 1000 MPa º³ÏÃÝÅ º Þ ¼ËÜÒ. Ë», ¼Ô ¼³, ¹ Ó Ë³ Õ Ø³ Ó, ¼ Åß ÇÑ¼Ô ß º [13]. Å, Ç» ÊÃÎ Ë Hopkinson ʱ (split Hopkinson tensile bar, SHTB) ÊÃÎ Á, Ð Swift Î Õ º³ÏÃÝÅ DP1180 º Þ (500 Ë 1750 s 1 ) ºÂ, ² Ð Crussard Jaoul «Ð Swift, Á DP1180 ÝÅ º Þ Å Õ Û, ² ÜÒ. 1 Î Î ÏÃÝÅ Û (Ó, %) ¼: C 0.19, Si 0.75, Mn 1.95, Cr 0.02, Nb 0.044, P 0.005, S 0.003, Fe º. Ïà ¼ 1.0 mm. Ïà  ¼ ̼ 50 mm 200 mm 1 mm, Gleeble 3500 Ü ± Ö Ö Ä Î. 10 /s ÞÆ 820 ² 150 s, 5 /s ÞÐÏ 710, 50 /s Ï ÈÖÆÏ 240, ± ÅË Ä, 240 s, ÃÏ, ² 1. 4%( Ý ) Í Ì, ² Û ¹½ (OM) ¹. Photoshop Ä Å Ç, ² Imagetool ² ß ÝÅ ¹ Õ µ ÌË Ý.» ÊÃÎ CMT4105 ¼Ô ܱ, ØÊÃÎ SHTB [9] ±, Î ±.» Þ¼ 0.001 s 1, ÊÃÎ ½ 2 Ö Þ¼ 500 Ë 1750 s 1.» Ë ÊÃÎ Ì ² 2. 2 κ  2.1 ² 3 ¼ DP1180 ÝÅ ¹. Â, Ù ¼ Å ËÑ ÝÅ. DP1180 ¹ ß Ã, DP1180 ÝÅ Õ µ ̼ 3.14 µm, Ì ² ѹ Nb, ѵ,  µ³ ; Õ 1 ÍĐ DP1180 Üĵ Õ³Õ Æ± Fig.1 Schematic diagram of continuous annealing for dual phase steel DP1180 2 к ÉÂÍĐÊÐ ÉÂÍĐÉ ˱ Fig.2 Geometries of tensile specimens for low strain rate (a) and high strain rate (b) tests (unit: mm)
1162 Ñ Ø Ø 48 Ý º, 68.7%, Ù Å ³ Ë Î ³, Ç Ê³ 1180 MPa. Õ ¼. ² DP1180 ÝÅ Õ Mn Ç º, ² ѹ Cr, Ç Ö Ë È, Ͼ Ë. µ ÃË ËÐ, Feret Þ [14] ¼ 1.35. 2.2» ² ½ ÍÌ ² 4 ¼ DP1180 ÝÅ Þ¼ 0.001 s 1» ÊÃÎ ÊÃÎ Ë Þ ¼ 500 Ë 1750 s 1 ºÂ.  Á, DP1180 ÝÅ ³ Þ ², ß Ðà ³ R p0.2 Ë Ê³ R m Þ Á Á, ³ Ö. 1 ¼ DP1180 ÝÅ» Ë Î ÊÃÛ Æ. Dz 4 Ë 1 Â, DP1180 Ý Å ³ ÞÁ Áº, ß Ðó Ç 723 MPa Á 988 MPa, ʳ Ç 1207 MPa Á 1515 MPa, ³ Ö.»³ Ç 0.60 Á 0.66, Þ DP1180 ÝÅ» ³ Ç. ² 5 ¼ DP1180 ÝÅ SHTB ÊÃÎ Þ Ë«ºÂ. ² ³ ØËÏ Ê, Þ Å¾ ß,  Á, SHTB ÊÃÎ Þ¾ Ç Ú,  ³Đ ß. 2.3 Ç È ÝÅ ¼, Å Õ Å ¼, Å, ½ ÜÒ Å¾ ¾ n ² Æ Õ ¾ ß ÝÅ [15,16]. Á, ½ Ð C J [17,18] Ð Swift ±, Đ Swift [19] ¼Ô, Đ Hollomm ¼Ô. ½ Ð C J DP1180 º³ ÏÃÝÅ Þ ¼±. DP1180 ÝÅ Þ ¼Ð Swift [12] ε p = ε 0 +cσ m (1) Õ, ε p ¼Î ; σ ¼Î ; ε 0 Ë c ¼¼Ô ; m ¼Ð Swift, Þ, m Ë. ² 6 ÁÑ DP1180 ÝÅ Þ¼ 0.001, 500 Ë 1750 s 1 ε p σ ºÂ ºÂ. 1 DP1180 Đ¼ ÌĐ Ï ÐËÄ Ü Table 1 Quasi static and dynamic tensile properties of DP1180 steel Strain Proof Tensile Percentage Yield rate strength strength elongation after ratio 3 DP1180 Üĵ Fig.3 OM image of DP1180 steel (F ferrite, M Engineering stress, MPa martensite, ND normal direction, RD rolling direction) 1800 1600 1400 1200 1000 800 600 400 200 0.001 s -1 500 s -1 1750 s -1 0 0 1 2 3 4 5 6 7 8 9 10 Engineering strain, % 4 DP1180 µ µ Ý ¹Á Fig.4 Engineering stress strain curves for DP1180 steel at different strain rates ε, s 1 R p0.2, MPa R m, MPa fracture A 50, % R p0.2 /R m 0.001 723 1207 9.0 0.60 500 875 1380 8.3 0.63 1750 998 1515 7.7 0.66 Strain rate, s -1 10 4 10 3 10 2 1750 s -1 500 s -1 10 1 0 2 4 6 8 10 12 14 16 18 Time, ms 5 DP1180 µ SHTB Ð ÉÂÍĐ Ý ÊÅ ¹Á Fig.5 Strain rate time curves for DP1180 steel under dynamic tensile test with split Hopkinson tensile bar (SHTB)
Ø 10 Ñ : DP1180 ÛÃ Ü ºÞÚÐ 1163 p 0.10 0.08 0.06 0.04 0.02 0.00 Measured 0.001 s -1 Measured 500 s -1 Measured 1750 s -1 Fitted 0.001 s -1 Fitted 500 s -1 Fitted 1750 s -1 0 200 400 600 800 1000 1200 1400 1600 1800, MPa 6 DP1180 µ µ Ý Swift ÍĐÖ ß Ï¹Á Fig.6 Measured and fitted true strain strain curves for DP1180 steel at different strain rates Þ¼ 0.001, 500 Ë 1750 s 1 Ë, ºÂ  R 2 ¼ 0.978, 0.991 Ë 0.985, º, ¼Î ºÂ È. ½ Ð Swift Â Õ DP1180 ÝÅ Þ. 2.4 ËÀ Das Ë Chattopadhyay [20] Ð C J Ñ Ä DP780 ÝÅ Û, Ý Ë ÝÅ ³ Ç, ². ÆÚÓ [15] Ð C J Ñ DP600 ÃÝÅ Ö Û, ² ÑÝÉ ¼ Ý «. Ð C J º³ÏÃÝ Å º Þ ³. (1) ¹ ²  РC J ln dσ dε p = (1 m)lnσ ln(cm) (2) Þ DP1180 ÝÅ Ð C J ln(dσ/dε p ) lnσ ºÂ ² 7.  Á,» Êà ÊÃ, DP1180 ÝÅ ³ 2 ¾ Þ., ÝÅ ³ 2 ¾, Ì Æ Ç ¼ Ý É [15,20], ε t. ² (2) Â, ln(dσ/dε p ) lnσ  Þм 1 m. 2 ¼ DP1180 ÝÅ Þ Ð C J ¼¾, m 1 Ë m 2 ÚÅ Ë ÚÆ Ð Swift. ² Ð Swift Õ, ¼, m ¼ Hollomm Õ n, Å, Ð Swift Õ m, Æ ³. Ö Þ (0.001 s 1 ) º Þ (500 Ë 1750 s 1 ), DP1180 ÝÅ ÚÅ Ö ³ ln(d /d p ) 11.5 11.0 10.5 10.0 9.5 9.0 8.5 8.0 7.5 Stage I t1 =3.12 Stage II t2 =2.75 0.001 s -1 500 s -1 1750 s -1 t3 =1.28 7.0 6.4 6.5 6.6 6.7 6.8 6.9 7.0 7.1 7.2 7.3 7.4 7.5 7.6 ln 7 DP1180 Üĵ µ Ý C J ¹Á Fig.7 Modified C J plot of DP1180 steel at different strain rates (ε t1, ε t2 and ε t3 indicate transition strain in the modified C J plot at strain rates of 0.001 s 1, 500 s 1 and 1750 s 1, respectively) 2 DP1180 ÞÆ ß Ñ Ð C J ½ Ø Table 2 Parameters related to strain hardening behaviour of DP1180 steel at different strain rates ε, s 1 Stage I Stage II Transition m 1 1 m 1 m 2 1 m 2 strain ε t, % 0.001 4.91 3.91 14.56 13.56 3.12 500 3.73 2.73 15.86 14.86 2.75 1750 3.04 2.04 16.77 15.77 1.28 Note: m 1 and m 2 indicate strain hardenging exponet in the modified swift mode of stage I and stage II, respectively Õ, ÚÆ º Æ. Ç 2  Á, ÚÅ Ö Þ Á, Þ 1 m 1 Ç 3.91 Á 2.04, m 1 Ç 4.91 Æ 3.04. Ì,, DP1180 ÝÅ Þ Á ÆÁ³. ÚÆ º Þ Á, Þ 1 m 2 Ç 13.56 Æ 15.77, m 2 Ç 14.56 Á 16.77, Ì, º, DP1180 ÝÅ Þ Á ÆÆ., ε t Þ Á Æ. 2.5 Ä ² 8 ¼ DP1180 ÝÅ Þ¼ 1750 s 1 Î ÝË ÎÁ TEM Ê. º Þ, ÝÅ Õ µ ³ ÕÔÐ«Ç Î. Ö, µ Ä Õ Î µ, ¼ Î, Ô Î Á. Ç ² 8 Õ µ Ä Õ Î ÎÁ Î ÎÁ Ç Î. Dz 8 Õ Â, µ ÕÊ Å [21] (cell block, CB), ¼ Î, Ì Å ²Å α (dense dislocation wall,
1164 Ñ Ø Ø 48 8 DP1180 Üĵ Ý» 1750 s 1 Í TEM É Fig.8 TEM image of dislocation structure in DP1180 steel deformed at strain rate of 1750 s 1 (Area A is larger cell block with 0.7 0.8 µm; areas B and C are smaller cell blocks with about 90 nm) DDW) ½. ² 8 Õ ¾ A ¼ Å, Ì ¼ 0.7 0.8 µm; ¾ B Ë C ¼ Å, Ì ¼ 90 nm. Ì ¼, ŵ Þ, µ Õ ¾ Åß «, µ ¾ «, Ç µ Æ, ² 8 Õ ²Å α ½ Å. ÌÖ µ Î, ¼Ñ Ö¼Ô Æ Ç [22]. DP1180 ÝÅ, Þ, ¼Ô РƲ, ¼Ô Á ¹ [23]. Î Ë«Á, ¾ Ý, Å, µ Õ, µ ³ ¹Æ µ ̼ 0.7 0.8 µm Å ¹, ² Þ ¾ «ÖÆ, 90 nm ŵ. ½ ÅË Î ¼ Î Ó (geometrically necessary boundary, GNB) [21,24], ² Ì GNB Ê DP1180 ÝÅ º Þ Å Ð«, ³Åß Þ, Ì DP1180 ÝÅ Þ Á ³ Á Ã Þ Ì. ² 9 ¼ DP1180 ÝÅ Þ 1750 s 1 TEM Ê.  Á, Ç ËÁ Æ, Ç Õ. Æ Ô Ç Î, Ì Î Ä, Æ Æ» ² Ç. ص, Õ DP1180 ÝÅ ± º Þ ÊÃÎ, Ì¼Ö Þ» Û.» Å Â Å¾Ó Å,  ¼ ž Å 9 DP1180 Üĵ Ý 1750 s 1 Ð TEM É Fig.9 TEM image of plastic deformation of martensite for DP1180 steel at strain rate of 1750 s 1. Å» ÊÃ, ² º ÊÃÅ Õ ¹ Ë Ó, Ç Æ Ë«Æ½¹ È Õ, Ç ¹ ɺ. É T  ² «[25,26] : T = G ρc v = η ρ ε2 ε 1 σ c v dε (3) Õ, G ¼Ü ÆË ÆÝ ; ρ ¼¼Ô, ¼ 7.8 g/cm 3 ; c v ¼Ó, ¼ 0.48 J/(g K); η ¼ Ý, ¼ 0.95; ε 1 ¼ Î, ¼ 0; ε 2 ¼ Î ; ε ¼Î ; σ ¼Î. Å (1)  «Á DP1180 ÝÅ Þ¼ 1750 s 1 Ë, T=103. ²ÅÂ, Å Õ É¼ 103, º Þ ¼Ô ¹, Å, µ ³ º, É, ÖÑ» ³, ± Ç. ² 7 Ë 2, ÚÅ Ö, Þ Á m Æ, ÆÁ³. ÌÙ ² DP1180 ÝÅ Ù ², Þ º, Õ Î Á, Î Ë Ó Î Á. Ì Ñ DP1180 ÝÅ R p0.2 Þ Á Á. DP1180 ÝÅ º Þ Ç Å¾ Þ³ Ë É Ë «Å ¾ Å : Å, º Þ, ¼ ÔЫ, Î Á, Î «Ì Ç«, ¼¼Ô ³ Á ; ØÅ, É ¼Ô, Î «, ¼Ô³ Ö. Å, DP1180 ÝÅ º Þ Ê³ Ð Ì ¾ Ç, ² ʳ Þ Á Á,
Ø 10 Ñ : DP1180 ÛÃ Ü ºÞÚÐ 1165 º Þ, Ë Þ³ É. ² 7 Ë 2, ÚÆ º, Þ Á m Á, ÆÆ. Ë [16,17,20] Ð C J ÁÑÝÅ» ÜÒ: ÚÅ, ³Â Î Å Ç ; ÚÆ, Å Ë ¹ Ç.  Á, Å Ç ÚÆ ÆÆ Ù. ²² 8 Ë 9 Â, ÚÆ ÆÆ ¼: Å, É Ç, Ô Å Å ÆÆ; Æ, ² Æ Å Î, Å», ºÑ Í, Ç. Õ ¾ DP1180 ÝÅ ÚÆ Õ Æ Þ Á Æ, Ë ε t Þ Á Æ. 3 º (1) Ð Swift Î Â Õ DP1180 ÝÅ º Þ ÊÃÕ. (2) Ð C J Ñ DP1180 ÝÅ Û,» Ë ÊÃ, Ê : ÚÅ, Þ Á Æ Á³; ÚÆ, Þ Á ÆÆ; Ý É Þ Á Æ. (3) DP1180 ÝÅ º Þ, ³ ² Ð Þ ÀÒ, Î Å. Ö, Å ÖÆ Å, Ì ¼ 90 nm. ² Î Ó Ê, DP1180 ÝÅ º Þ Å Ð«, ³Åß Þ. (4) DP1180 ÝÅ º Þ, É Ç, Ô Å Å ÆÆ. ² Æ Å Î, ºÑ Í, Ç. ÚÆ Æ Þ Á Æ, Ë ÝÉ Þ Á Æ. ¼ÁÅ [1] Chongthairungruang B, Uthaisangsuk V, Suranuntchai S, Jirathearanat S. Mater Des, 2012; 39: 318 [2] Giri S K, Bhattacharjee D. J Mater Eng Perform, 2012; 21: 988 [3] Pouranvari M. Mater Sci Eng, 2012; A546: 129 [4] Queiroz R R U, Cunha F G G, Gonzalez B M. Mater Sci Eng, 2012; A543: 84 [5] Ahmad E, Manzoor T, Ziai M M A, Hussain N. J Mater Eng Perform, 2012; 21: 382 [6] Nouri A, Saghafian H, Kheirandish S. Int J Mater Res, 2010; 101: 1286 [7] Calcagnotto M,Adachi Y,Ponge D,Raabe D. Acta Mater, 2011; 59: 658 [8] Sun X, Choi K S, Soulami A, Liu W N, Khaleel M A. Mater Sci Eng, 2009; A526: 140 [9] Huh H, Kang W J, Han S S. Exp Mech, 2002; 42(1): 8 [10] Deng Z J, Liu J, Wang H, Li P H. J Mater Therm Treat, 2011; 32: 111 (ÔÆ, Ù º, Ò, Ê.»Ó à Ú, 2011; 32: 111) [11] Kamp A, Celotto S, Hanlon D N. Mater Sci Eng, 2012; A538: 35 [12] Colla V, De Sanctis M, Dimatteo A, Lovicu G, Solina A, Valentini R. Metall Mater Trans, 2009; 40A: 2557 [13] Sung J H, Kim J H, Wagoner R H. Int J Plast, 2010; 26: 1746 [14] Beynon N D, Jones T B, Fourlaris G. Mater Sci Technol, 2005; 21: 103 [15] Kuang S, Kang Y L, Yu H, Liu R D. J Mater Eng, 2009; (2): 11 ( Ù, Ö, É, Ù.»Ó, 2009; (2): 11) [16] Ramos L F, Matlock D K, Krauss G. Metall Trans, 1979; 10A: 259 [17] Samuel F H. Mater Sci Eng, 1987; 92: L1 [18] Jha B K, Avtar R, Dwivedi V S, Ramaswamy V. J Mater Sci Lett, 1987; 6: 891 [19] Swift H W. J Mech Phys Solids, 1952; (1): 1 [20] Das D, Chattopadhyay P P. J Mater Sci, 2009; 44: 2957 [21] Yu Y N. Fundamentals of Materials Science. Beijing: High Education Press, 2006: 566 (¹.»ÓÀÚÙÂ. : ¹Ò À À, 2006: 566) [22] Winther G, Jensen D J, Hansen N. Acta Mater, 1997; 45: 5059 [23] Sha G Y, Sun X G, Liu T, Zhu Y H, Feng X G. Chin J Mater Res, 2010; 24: 567 ( À, Î, Ù, ½, γ.»Óß Ú, 2010; 24: 567) [24] Hughes D A, Hansen N, Bammann D J. Scr Mater, 2003; 48: 147 [25] Wu Z Q, Tang Z Y, Li H Y, Zhang H D. Acta Metall Sin, 2012; 48: 593 ( ²,,, ÅÆ. ÒÚ, 2012; 48: 593) [26] Wu C C, Wang S H, Chen C Y, Yang J R, Chiu P K, Fang J. Scr Mater, 2007; 56: 717 (ÞÖ Ó: ÜØÒ)