Determination of Strain Rate Sensitivity (SRS) for Grain Size Variants on Nanocrystalline Material Produced by ARB and ECAP

Transcription

1 Wol Acaemy of Science, Engineeing an Technology Inenaional Jounal of Maeials an Meallugical Engineeing Vol:9, No:, 05 Deeminaion of Sain Rae Sensiiviy (SRS) fo Gain Size Vaians on Nanocysalline Maeial Pouce by ARB an ECAP P. B. Sob, A. A. Alugongo, T. B. Tengen Inenaional Science Inex, Maeials an Meallugical Engineeing Vol:9, No:, 05 wase.og/publicaion/ Absac Mechanical behavio of 608T6 aluminum is invesigae a iffeen empeaues. The sain ae sensiiviy is invesigae a iffeen empeaues on he gain size vaians. The sensiiviy of he measue gain size vaians on 3-D gain is iscusse. I is shown ha he sain ae sensiiviies ae negaive fo he gain size vaians uing he efomaion of nanosucue maeials. I is also obseve ha he sain ae sensiiviies vay in iffeen ways wih he equivalen aius, semi mino axis aius, semi majo axis aius an majo axis aius. Fom he obaine esuls, i is shown ha he vaiaion of sain ae sensiiviy wih empeaue suggess ha he sain ae sensiiviy a he low an he high empeaue ens of he 608T6 aluminum ange is iffeen. The obaine esuls eveale ansiion a iffeen empeaue fom negaive sain ae sensiiviy as empeaue incease on he gain size vaians. Keywos Nanosucue maeials, gain size vaians, empeaue, yiel sess, sain ae sensiiviy. S I. INTRODUCTION TRAIN RATE SENSITIVITY (SRS) is impoan in eemining he efomaion mechanisms of nanosucue maeials []. Seveal suies on SRS have been caie ou an his has conibue o he pesen conovesies on nanomaeials mechanical popeies. Mos eseaches have epoe ha SRS vaie wih he pocessing paamees an he micosucual vaiables []-[4]. The vaying efiniion of moel equaions of SRS conibues gealy o he pesen conovesies on nanomaeials mechanical popeies. The iffeen mehos an echniques o compue SRS ae explaine in his secion. A. The Mehos of Tensile Tes Duing his echnique, a jump es was conuce using a univesal esing machine by inceasing an eceasing he sain aes by 0 % fo evey 00% incemen of elongaion [5]. The SRS values fo vaious sains wee compue using he expession [5]. P. B. Sob an A. A. Alugongo ae wih he Depamen of Mechanical Engineeing, Faculy of Engineeing an Technology, Vaal Univesiy of Technology, Vanebijlpak 900, Pivae Bag X0, Souh Afica ( baonhe_sob@ock .com, alfayoa@vu.ac.za). T. B. Tengen is wih he Depamen of Inusial Engineeing an Opeaions Managemen, Faculy of Engineeing an Technology, Vaal Univesiy of Technology, Vanebijlpak 900, Pivae Bag X0, Souh Afica ( Thomas@vu.ac.za). SRS σ log σ ε log ε F ( + e ) So F log log F ( + e ) So F ɺ V ( e) L V + () o log log ɺ V ( + e) L V wheeσ an σ ae he flow sesses coesponing o insananeous sain aes ε anε. F an F ae he foces an V an V ae he coss-hea spees befoe an afe he jump. The SRS values a a single sain was calculae, a a fixe sain ae using he expeimenal aa of he coss-hea spees V an V wih he coesponing foces F an F. A seies of SRS values wee compue fom he jump es an ploe as a funcion of sain aes. The SRS was measue a iffeen empeaues in he sain ae jump ensile es []. B. The Compession an Vishay Mico Measuemen Techniques Sabiov [6] suie he elaionship beween SRS of he flow sess an he opeaive efomaion mechanisms in he UFG Al Mg Si (Al608) alloy une compession. Thei esuls of compession esing eveale ha incease SRS ue o gain bounay sliing an mico shea baning offes enhance uciliy a low sain aes. Anohe suy on SRS by [7] eveale ha, he SRS can be calculae by measuing he sain wih a Vishay mico measuemen goup highelongaion uniaxial sain gauge affixe o he mile of he gauge secion. The esuls eveale incease in yiel sengh when he maeial sain-aes ae incease. I was howeve obseve ha a high efomaion empeaue he SRS incease wih inceasing efomaion empeaue []-[4]. Seveal suies have shown ha nanomaeials ae vey sensiive o empeaue []-[5]. Vaying empeaue uing efomaion of convenional maeials o nanosucue maeials affec he SRS of maeials []-[7]. Tempeaue has a vial ole o play uing gain efinemen since all sevee plasic efomaion (SPD) echniques involve hemomechanical pocesses. Kuma [8] epoe ha, he hemoynamic popeies of nanomaeials epen on he size an shape of hei vibaion enegy. Lee an Chiou [9]-[0] also obseve ha he SRS incease wih eceasing gain size. Kuma [8] evelope a heoeical moel an suie he size an shape effec on sain an sain ae. The heoeical esuls wee compae wih expeimenal esuls in he o Inenaional Scholaly an Scienific Reseach & Innovaion 9() schola.wase.og/ /

2 Wol Acaemy of Science, Engineeing an Technology Inenaional Jounal of Maeials an Meallugical Engineeing Vol:9, No:, 05 Inenaional Science Inex, Maeials an Meallugical Engineeing Vol:9, No:, 05 wase.og/publicaion/ eseach an i was shown ha he expeimenal aa suppos he heoeical evelope moel. Guisbies [] evelope a moel peicing he size epenence of meling an cohesive enegy of nanocysalline. Fom he suies, obaine esuls wee compae wih iffeen moels peicing he size epenence. Zhang [] also emonsae ha, a simple moel, fee fom any ajusable paamee can be evelope fo he meling enhalpy an meling enopy of nanocysals. The iea was base on Mo s equaion fo meling enhalpy an meling enopy fo non-semiconuco cysals moel of size epenen meling empeaue. The bulk popeies of cysals epen on hei sucue bu a nanoscales, in aiion o he sucue hei size an shape ae impoan faco which influences hei popeies. The mos impoan chaaceisic of maeials a nanoscales is hei high suface o volume aio which affecs hei hemoynamic popeies an SRS []. I is now well known ha he meling empeaue of nanopaicles epens on hei size [3]; hus size an empeaue ae impoan paamees when suying nanomaeials mechanical popeies. Alhough he size-epenen popeies ae so useful, a unique aemp o esablish a quaniaive moel escibing he size epenence of SRS, base on simple consieaion of suface/volume aio, canno saisfacoily inepe he sochasic naue of gain size. Thus, i is necessay o moel quaniaively SRS as funcion of gain size vaians (3-D gain). In his pape, he SRS is compue on gain size vaians an he effec of pocessing empeaue on SRS ae iscusse fo a 3-D gain efome by Accumulaive Roll- Boning (ARB) an Equal Channel Angula Pessing (ECAP). The popose moels ae ese wih aa fom gain efomaion in nanocysalline aluminum samples. II. METHODOLOGY The mos impoan mechanical chaaceisic of supeplasic maeial is he high sain ae sensiiviy of is flow of sess [], [3]. The chaaceisic equaion which escibes maeial yiel sess ( σ ( ) ) an sain ae ( εɺ ) can be elae hough a powe law usually wien as σ m ( ) Kɺ ε () whee m is he empeaue epenen sain ae sensiiviy (SRS) faco. K is a popoionaliy consan ha is being ignoe by aking logaihm of boh sies of he equaion when he SRS is compue as ( σ ( ) ) ( ɺ ε ) log m (3) log By employing he iffeen moels of sain( ε ) fo 3-D gain uing gain efinemen, he coesponing sain aes ( εɺ ) fo,, an 3 uing gain efinemen ae efine as ( ) ZV ( ) CDW M + c ( ) εɺ (4) whee c local ciical gain size, Z an D ae Consans, W()incemen of he Wiene pocess, V efine ae of gain beakage, CD, + CD 4(Hm)(h 0 )/((k)(t)), T m T{ln(m 0 /m) an M 0 M 0 exp{-t m (inf)/t}. ( εɺ ) ( ) εɺ 3 whee O an I ae consans 3 Raio 3 3 O + IW Raio ( ) (5) (6) ( εɺ ) (7) M M0 on nanomaeial s gain subjece o plasic efomaion is given by [4]. The maeial yiel sess σ ( ) 3 ' ( ) + σ ( ) A B C (8) σ 0 ' wheeσ 0 σ 0 +K is bulk yiel sess, A K is HPR B K hh / RT, popoionaliy consan, [ m ] C K [ hh / RT ], K m is a consan, h is aomic iamee in he case of meal, H m is he bulk meling enhalpy, R is ieal gas consan, T is he oom empeaue, K > 00K an σ 0 >0K. Equaions ()-(8) ae solve simulaneously using Engineeing Equaion Solve sofwae (F-Cha Sofwae, Mason, W53744, USA) an also employing he fac ha, gain size isibuion evolve as lognomal isibuion [5]. III. RESULTS AND DISCUSSION τ To es he moels popose in his epo, he aa fom (nanocysalline) aluminum sample (some of which ae foun in ohe epos, [6]) ae use, which ae M 0 0.0nm s -, m4, CC, a0.90, D0-4, h 0 0.5nm, T m ( )933.47K, CV 0 0.3, Raio 0.8, Raio.07, H m ( )0.7KJMol, σ 0 6.7MPa, K.3, σ MPa, Inenaional Scholaly an Scienific Reseach & Innovaion 9() schola.wase.og/ /

3 Wol Acaemy of Science, Engineeing an Technology Inenaional Jounal of Maeials an Meallugical Engineeing Vol:9, No:, 05 K30.77MPa_nm /, R8.3JK - mol -, T 300K. The aiional aa obaine fom his wok ae O0.0035, I., c.95, 0 00nm, Z0.4 an The τ aiional aa wee obaine hough cuve fiing of he empiical aa fom he iffeen measues of he sizes. The obaine esuls ae pesene in he plos below. Inenaional Science Inex, Maeials an Meallugical Engineeing Vol:9, No:, 05 wase.og/publicaion/ Fig. Yiel sess an sain aes a iffeen empeaues an SRS calculae a he slops of he gain size vaians TABLE I THE RESULTS OF SRS MEASUREMENT AT SIX TEMPERATURES ON GRAIN SIZE VARIANTS Tempeaue ( o C) SRS) (SRS) (SRS) 3 (SRS) The SRS values fo he gain size vaians wee calculae fom he slopes of he plos a iffeen empeaue using ( log( σ ( ) )) an ( log( εɺ )); hese values ae pesene in Table I. IV. THE SENSITIVITY OF NANOMATERIALS The vaiaion of SRS wih empeaue is shown in Fig. fo six empeaues. I is obseve ha, a a empeaue ange fom oom-empeaue up o 400 o C, no ponounce SRS is Inenaional Scholaly an Scienific Reseach & Innovaion 9() schola.wase.og/ /

4 Wol Acaemy of Science, Engineeing an Technology Inenaional Jounal of Maeials an Meallugical Engineeing Vol:9, No:, 05 Inenaional Science Inex, Maeials an Meallugical Engineeing Vol:9, No:, 05 wase.og/publicaion/ foun fo. By inceasing he esing empeaue fuhe, he SRS also incease an ecease fo gain size vaians. The iffeen esuls of SRS fo gain size vaians ae ue o iffeen gain cuvaues uing gain efinemen. The highe amoun of high angle gain cuvaues is he main eason fo he enhance SRS an he lowe amoun of low angle gain cuvaues is he main eason fo a lowe SRS fo gain size vaians. The esuls obaine inicae a change in he efomaion mechanism of he ula-fine gain egime ue o iffeen gain cuvaues uing gain efinemen. The hemal acivae ecovey pocesses aking place a he gain cuvaues ae he ominaing efomaion mechanisms. Suying he effec of cuvaue on SRS i is obseve fom Fig. ha, a a empeaue of 400 o C iffeen SRS ae eveale fo he gain size vaians. Fom he iffeen SRS eveale a a empeaue of 400 o C he maeial SRS is high fo aius measue along 3 since he gain cuvaue fo 3 is highe when compae wih he cuvaues of, an. When he empeaue incease fom 400 o C o 500 o C he SRS incease along 3 an ecease along, an since he gain cuvaue of 3 is highe when compae wih he cuvaues of, an. The SRS eceases moe along when compae o while an 3 incease a a empeaue of 400 o C o 500 o C since he gain cuvaue of is lowe han he cuvaue of, an 3. The vaiaion of SRS wih empeaue in gain size vaians suggess ha, he SRS fo 608T6 aluminum a he low an he high empeaue ens ae iffeen. This suggess ha, iffeen ynamic sain aging (DSA) mechanisms ominae he behavio of,, 3 an a iffeen empeaue anges since a exemely low empeaue he SRS is small an a high empeaue he SRS incease an esuls o maeial haening. The high empeaue behavio oes no appea o be ue o sucual changes such as pecipiaion, which coul change he naue of he ae conolling obsacles o islocaion moion. Fom his suy, i has been eveale ha nanomaeials ae vey sensiive o empeaue uing manufacuing. V. THE STRAIN RATE SENSITIVITY AND GRAIN SIZE VARIANTS The pimay easons fo incease an ecease in SRS is ue o iffeen gain cuvaues, gain cuvaue iffusion, gain cuvaues sliing meiae by islocaion aciviy an conolle plasiciy on he gain size vaians uing gain efinemen. I is obseve fom Fig. 3 ha he SRS vay wih gain size vaians ue o iffeen gain cuvaues. I is obseve fom Fig. 3 ha a a gain size of 0nm iffeen SRS ae eveale fo he gain size vaians. Fom he iffeen SRS eveale a a gain size of 0nm he maeial SRS is high fo aius measue along 3 an low fo aius measue along, an since he gain cuvaue of is highe han he cuvaues of, an. I is obseve a a gain size of 40nm ha SRS incease when measue along,, an ecease along 3 ue o highe gain cuvaues of,, an lowe gain cuvaue of 3. I is also obseve a a gain size of 60nm o 80nm ha, he SRS incease along 3,, an ecease along. I is fuhe obseve a a gain size of 00nm ha, he SRS incease moe along when compae o, an 3 ue o highe gain cuvaue of. Fig. Vaiaion of (SRS) wih Tempeaue a six empeaues wihin he negaive SRS ange fo gain size vaians Fig. 3 Vaiaion of he sain ae sensiiviy (m) wih size (nm) a six empeaues wihin he negaive SRS ange The esuls in Fig. 3 show a clea fashion ha, he SRS coninuously incease an ecease a iffeen empeaues on gain size vaians. The incease in SRS is iecly elae o a change in he ae conolling mechanism fo plasic efomaion. Thee have been epos of boh incease an ecease SRS wih eceasing gain size in meals [], [7] simila o he esul obaine in his eseach. VI. CONCLUSIONS The cuen wok was aime a eemining he effec of SRS on gain size vaians. To achieve ha he chaaceisic σ an equaion which escibes maeial yiel sess ( ( ) ) sain ae( εɺ ) was moifie o be applicable o 3-D gains. The moels of sain fo 3-D gain wee also ansfome ino Inenaional Scholaly an Scienific Reseach & Innovaion 9() schola.wase.og/ /

5 Wol Acaemy of Science, Engineeing an Technology Inenaional Jounal of Maeials an Meallugical Engineeing Vol:9, No:, 05 Inenaional Science Inex, Maeials an Meallugical Engineeing Vol:9, No:, 05 wase.og/publicaion/ a moel of sain ae. Fuhemoe, he sochasic naues of he gain size vaians wee also aken ino consieaion I can be conclue ha he effec of efomaion empeaue le o iffeen SRS ue o iffeen gain cuvaues of he gain size vaians. I was also obseve ha, he SRS of he gain size vaians ecease an incease wih inceasing empeaue. The incease an ecease in SRS wih empeaue fo he gain size vaians suggess ha, he SRS fo 608T6 aluminum a he low an he high empeaue ens ae iffeen. This inicaes ha, iffeen ynamic sain aging (DSA) mechanisms ominae he behavio of he gain size vaians a iffeen empeaue anges since a exemely low empeaue, he SRS is small an a high empeaue; he SRS incease an esuls o maeial haening. I can be conclue ha incease in empeaue impac he SRS of nanosucue uing gain efinemen. ACKNOWLEDGMENT This maeial is base on he wok which is suppoe financially by he Naional Reseach Founaion (NRF) an Vaal Univesiy of Technology (VUT). REFERENCE [] Keicbeg, A. & Pokoshkin, S. & Bailovski, V. & Guneov, D. & Khomuov, M. 04. Influence of he sain ae an efomaion empeaue of he efomabiliy of Ti Ni SMAs: A peliminay suy. Maeial Science an Engineeing 63(04)009 [] Picu, R. C. & Vincze, G. & Ozuka, F. & Gacio, J. J. & Bala, F. & Maniay, A. M Sain ae sensiiviy of he commecial aluminum alloy AA58-O. Maeials Science an Engineeing A 390 (005) [3] May, J. & Hoppel, H. W. & Goken, M Sain ae sensiiviy of ulafine-gaine aluminium pocesse by sevee plasic efomaion. ScipaMaeialia 53(005)89-94 [4] Lee, W. S. & Lin, C. F. &Chen, T. H. & Hwang, H. H Effecs of sain ae an empeaue onmechanical behavio of Ti 5Mo 5Z 3Al alloy. J Mech Behav Biome Mae 008; (4): [5] Anon, S. & Bane, S. & Maeyz, F Deeminaion of he sainae sensiiviy an he acivaion enegy of efomaion in he supeplasic aluminium alloy Al-Mg-Mn-Sc. RMZ Maeials an Geoenvionmen, Vol. 56, No. 4, pp , 009 [6] Sabiov, I. & Bane, M. R. & Esin, Y. & Hogson, P. D The effec of sain ae on he efomaion mechanisms an he sain ae sensiiviy of an ula-fine-gaine Al alloy. Scipa Maeialia 6 (009) 8 84 [7] Ba, L. B. &Thomas, B. C. &Mois, F. D The Sain-Rae Sensiiviy of High-Sengh High-Toughness Seels. Sania Repo San [8] Kuma, R. & Shama, G. & Kuma, M. 03. Effec of size an shape on he vibaional an hemoynamics popeies of nanomaeials. Jounal of hemoynamics Vol. pp 5 [9] Lee, W. S. & Lin, C. F. &Chen, T. H. & Hwang, H. H Effecs of sain ae an empeaue onmechanical behavio of Ti 5Mo 5Z 3Al alloy. J Mech Behav Biome Mae 008;(4): [0] Chiou, S. T. & Tsai, H. L. & Lee, W. S Impac mechanical esponse an micosucual evoluion of Ti alloy une vaious empeaues. J Mae Pocess Technol009;09 (5):8 94. [] Guisbies, G. 00. Size epenen maeials popeies owas a univesal equaion. Nanoscale Reseach Lees, Vol. 5, No.7, pp [] Zhang, Z. & Lii, X. X. & Jiang, Q Finie size effec on meling enhalpy an meling enopy of nanocysals. Physical B Vol. 70, No. 3-4, pp [3] Xiong, S. & Qi, W. & Cheng, Y. & Huang, B. & Wang, W. & Li, Y. 0. Univesal elaion fo size epenen hemoynamic popeies of meallic nanopaicles. Physical Chemisy Chemical Physics, Vol. 3, No., pp [4] Zhao, M. & Jiang, Q Revese hall-pech elaionship of meals in nanomee size. Emeging Technologies-Nanoeleconics, IEEE Confeence on Vol. pp , (0-3 Jan. 006) [5] Tengen, T. B. & Iwankiewicz, R Moelling of he gain size pobabiliy isibuion in polycysalline. Composie Sucues 9(009) [6] Tengen, T. B. 008.Analysis of Chaaceisic of Ranom Micosucues of Nanomaeials. PhD. Thesis. Wiwaesan Johannesbug. [7] Meyes, M. A. & Misha, A. & Benson,. J Mechanical popeies of nanocysalline maeials. Pogess in Maeials Science 5(006) Inenaional Scholaly an Scienific Reseach & Innovaion 9() schola.wase.og/ /