Mechanical alloying of Fe100−x−yNbxBy (x = 5, 10; y = 10, 15): from pure powder mixture to amorphous phase

In e me allics. Vol. 16. Núm. 9. 2008. Pag. 1073-1082 h p://dx.doi.o g/10.1016/j.in e me .2008.06.006 1 Mechanical alloying o Fe100-x-yNbxBy (x=5, 10; y=10, 15): F om pu e powde mix u e o amo phous phase J.J. Ipus, J.S. Blázquez, V. F anco, A. Conde* Dp o. Física de la Ma e ia Condensada, ICMSE-CSIC, Uni e sidad de Se illa, P.O. Box 1065, 41080, Se illa, Spain. Abs ac The mechanical alloying p ocess o Fe75Nb10B15 and Fe85Nb5B10 sys ems has been s udied om an ini ial mix u e o elemen al powde s. The amo phiza ion p ocess is moni o ed by X- ay di ac ion, Mössbaue spec oscopy and magne iza ion measu emen s. An amo phous phase (wi h a Cu ie empe a u e o ~250 K) is o med a e 400 h milling only o Fe75Nb10B15 alloy, whe eas a bcc supe sa u ed solid solu ion is he inal p oduc a e milling Fe85Nb5B10 alloy. Fo bo h cases, a dispe sion o ~10 % in he Fe con en o he powde pa icles pe sis s a e 400 h milling. Powde pa icle size, C con en and la ice pa ame e o bcc phase a e la ge o he alloy wi h he highes Nb con en . Keywo ds: A. Nanos uc u ed in e me allics; A. Magne ic in e me allics; C. Mechanical alloying and milling. *Co esponding au ho : P o . A. Conde Depa amen o de Física de la Ma e ia Condensada. Uni e sidad de Se illa. Apa ado 1065, 41080 Se illa (Spain). Phone : (34) 95 455 28 85/ Fax : (34) 95 461 20 97 E-mail: [email p o ec ed] In e me allics. Vol. 16. Núm. 9. 2008. Pag. 1073-1082 h p://dx.doi.o g/10.1016/j.in e me .2008.06.006 2 1 In oduc ion Nanoc ys alline ma e ials a e de ined by a c ys al size below 100 nm. As a limi , amo phous ma e ials a e solid sys ems whe e he s uc u al long ange o de is los . These ma e ials ha e ecei ed much a en ion due o hei physical p ope ies (mechanical and magne ic), which a e clea ly di e en om hose exhibi ed by con en ional mic os uc u es and, in some cases, imp o e hei echnological applicabili y [1,2,3]. One way o ob ain nanoc ys alline ma e ials is by pa ial de i i ica ion o a p ecu so amo phous alloy du ing con olled he mal annealing. This echnique con ols he mic os uc u e o ma e ials and hus op imizes he p ope ies o he inal p oduc . Ano he possibili y is mechanical alloying, which has become a e y e sa ile echnique o di ec ly p oduce me as able mic os uc u es (amo phous, nanoc ys allines, supe sa u a e solid solu ion, e c) [1] om elemen al powde s o alloys. Du ing his milling p ocess he ma e ial is submi ed o ac u e and cold welding phenomena, as well as in ensi e plas ic de o ma ion, which de ine he powde mo phology, mic os u u e and p ope ies. The con inuous s o ing o de ec s in he c ys alline phase du ing milling p ocess uns abilizes i , leading o nanoc ys alline and/o amo phous s uc u es [1]. Nanoc ys alline Fe-M-B ype alloys (M= Z , Nb, e c), so-called Nanope m [4], a e a ac i e due o hei so magne ic p ope ies a e op imum he mal ea men and a e used in comme cial applica ions such as elecommunica ions, mic o de ices and powe elec onics [5,6]. Al hough hese sys ems a e gene ally ob ained by apid quenching and subsequen annealing, nanoc ys alline alloys o hese composi ions can be di ec ly ob ained by mechanical alloying o elemen al powde s. As so magne ic p ope ies depend on he s uc u e o he ma e ial [7,8,9], i s s uc u al cha ac e iza ion In e me allics. Vol. 16. Núm. 9. 2008. Pag. 1073-1082 h p://dx.doi.o g/10.1016/j.in e me .2008.06.006 3 is a e y impo an ask o unde s and he sys em beha io and o p edic i s possible echnological capabili ies. In his s udy, wo Fe100-x-yNbxBy (x=5, y=10 and x=10, y=15) alloys we e p oduced by mechanical alloying om a mix u e o pu e elemen s and hei mo phological, composi ional and mic os uc u al e olu ion, as well as hei he mal s abili y, we e s udied as a unc ion o milling ime. The amo phiza ion o he e na y FeNbB sys em by apid quenching me hods has been s udied p e iously [10]. Whe eas composi ions simila o Nb10 can be ob ained in amo phous s uc u e, hose simila o Nb5 can no be ob ained as amo phous. 2 Expe imen al Fe100-x-yNbxBy (x=5, y=10 and x=10, y=15) composi ions we e p epa ed by ball milling in a plane a y mill F i sch Pul e ise e 4 Va io om elemen al powde s ( 99 % pu i y), wi h pa icle size d <200 m o Fe and Nb and d <1 mm o B. Fo simplici y, he s udied alloys will be named in he ollowing by hei Nb con en : Nb10 o Fe75Nb10B15 and Nb5 o Fe85Nb5B10. The ini ial powde mass was 30 g and he ball o powde a io was 10:1. The o a ional speed o he disk which suppo s he ials was 150 pm and ha o he ials was 300 pm in opposi e di ec ion. A e selec ed imes, some powde was aken ou om he ials o cha ac e ize he mo phology, composi ion, mic os uc u e and he mal e olu ion. The opening and closing o he ials was done unde a gon a mosphe e in a Sa on Omega glo e box o a oid oxygen and humidi y con amina ion. Pa icle size dis ibu ion and mo phology we e s udied by scanning elec on mic oscopy (SEM) using seconda y elec ons (SE) and backsca e ed elec ons (BSE) modes in a Jeol JSM-6460 LV ope a ed a 30 kV. Composi ional e olu ion was s udied In e me allics. Vol. 16. Núm. 9. 2008. Pag. 1073-1082 h p://dx.doi.o g/10.1016/j.in e me .2008.06.006 4 by ene gy dispe si e X- ay (EDX) analysis using an Incax-sigh o Ox o d Ins umen s. Phase composi ion and s uc u e we e s udied om X- ay di ac ion (XRD), using Cu K adia ion, and Mössbaue spec ome y (MS). Mössbaue spec a we e eco ded a oom empe a u e in a ansmission geome y using a 57Co(Rh) sou ce. Values o he hype ine pa ame e s we e ob ained by i ing wi h NORMOS p og am [11]. The isome shi , I, was quo ed ela i e o ha o -Fe a oom empe a u e. Magne iza ion was measu ed using a maximum applied ield o 1.5 T, in he empe a u e ange om 77 o 440 K, e e y 15 K, in a ib a ing sample magne ome e (VSM). The alues o magne iza ion we e ob ained by ex apola ion o ze o ield o he linea i ing o he high ield magne iza ion. The mal cha ac e iza ion o he samples was s udied by di e en ial scanning calo ime y (DSC) using a Pe kin-Elme DSC7 in A a mosphe e. 3 Resul s 3.1 Mo phology and composi ion Figu e 1 shows SEM images o bo h alloys ob ained a e di e en milling imes. Fo bo h alloys a sho milling imes, <20 h, he pa icles a e o med by join laye s and inclusions, which p esen di e en composi ion. In o de o app ecia e his he e ogenei y in mo e de ail, igu e 2 shows SE ( igu e 2a) and BSE ( igu e 2b) images aken on a ypical pa icle a e 2 h milling o Nb10 alloy. Figu e 2c shows EDX spec a aken on he di e en poin s ma ked in igu e 2a. The A spec um, on a da k inclusion, only shows he emission line o bo on besides he ypical backg ound a low ene gy, so his zone is ich in his ligh elemen . The B and C spec a show zones ich in Fe and Nb, espec i ely. The e o e, he he e ogenei y o he indi idual powde pa icles is e idenced o sho milling imes in he condi ions used in his s udy. In e me allics. Vol. 16. Núm. 9. 2008. Pag. 1073-1082 h p://dx.doi.o g/10.1016/j.in e me .2008.06.006 5 A e 20 h milling, he powde s show po es and c acks on hei su ace o Nb10 and Nb5 alloys bu no clea laye s and, o longe milling imes, 100 h, agglome a ion o powde is obse ed. This p ocess seems o depend on milling condi ions, as o he au ho ha e de ec ed agglome a ion o pa icles much ea lie o simila composi ions (e.g. a e 5 and 15 h o Fe84Nb7B9 alloy wi h mo e ene ge ic milling condi ions [12]). The pa icles ha o m hese agglome a es a e la ge o Nb10 han o Nb5 alloy. A e 400 h milling, he agglome a es a e no obse ed o Nb10 alloy bu , o Nb5 alloy, he pa icles a e s ill agglome a ed. F om SEM images, a s a is ical analysis o he a e age pa icle size e olu ion, <d>, has been pe o med o e ~100 pa icles pe sample (Figu e 3) o bo h alloys. A e 20 h milling, <d> inc eases o e <d> > 200 m o bo h alloys. As milling ime inc eases, a dec ease in <d> is obse ed and, abou 100 h milling, his alue is s abilized, being smalle o Nb5 alloy (~ 25 m) han o Nb10 alloy (~ 50 m). This indica es ha a s a iona y si ua ion be ween cold welding and ac u e has been achie ed. The composi ional e olu ion was s udied by EDX om a s a is ical se o ~20 pa icles o each sample. As B con en canno be quan i a i ely measu ed by EDX, composi ional analysis o he sys ems is e e ed o he ela i e amoun s o Fe and Nb. In igu e 4, his og ams o Fe con en o he powde pa icles a e p esen ed o Nb10 and Nb5 alloys a e di e en milling imes. Fo sho milling imes, ≤5 h, i is possible o ind Nb ich pa icles and a high ac ion o Fe ich pa icles in bo h alloys. A e 10 h milling, in Nb5 alloy a s ong educ ion in he b oadening o he composi ional dis ibu ion, ΔCFe, is obse ed (calcula ed as he di e ence in Fe/Fe+Nb a io be ween he Fe iches and he Fe poo es powde pa icles ound). Howe e , his educ ion occu s o 20 h in he Nb10 alloy, being a wide composi ional dis ibu ion o he alloy In e me allics. Vol. 16. Núm. 9. 2008. Pag. 1073-1082 h p://dx.doi.o g/10.1016/j.in e me .2008.06.006 6 wi h a highe Nb con en . Fo longe milling imes, > 20 h, he b oadening o he dis ibu ion o Fe con en is almos cons an and, a he end o he s udied ange, he e is no a unique composi ion bu a ce ain b oadening is ound (ΔCFe =16 a . % o Fe o Nb10 and 8 a . % o Fe o Nb5). Small Fe con amina ion is ha d o measu e in such Fe ich composi ions. Howe e , C is easily quan i ied as he ini ial powde mix u e o his s udy is C ee. The e o e, igu e 5 shows he C concen a ion as a unc ion o he milling ime. Fo bo h alloys, a linea inc ease wi h he milling ime is obse ed in he explo ed ange, being he amoun o C highe o Nb10 (~2 a . %) alloy han o Nb5 (~1 a . %) alloy a e 400 h milling, in ag eemen wi h he expec ed inc ease o ha dness as Nb inc eases in Fe based alloys [13]. Simila C con amina ion has been ound in o he ball milled sys ems [14]. 3.2 S uc u al e olu ion 3.2.1 X- ay di ac ion Figu e 6 shows he XRD pa e ns o bo h alloys as a unc ion o milling ime. Fo sho milling imes,  20 h, a sligh b oadening o (110) di ac ion peak o he α- Fe phase can be obse ed o bo h alloys. The ull wid h a hal maximum (FWHM) is app oxima ely he same o bo h alloys a his s age; FWHM inc eases om 0.26 o 0.52 ± 0.10º om 1 o 20 h, espec i ely. This e ec can be ela ed wi h he dec ease o he c ys alline size and an inc ease o mic os ains. A e 50 h milling, a s ong b oadening o (110) peak is obse ed, as well as a shi o lowe alues o 2 posi ion o his peak. Mo eo e , he di e en maxima o bcc- Nb a e no longe de ec ed. These e ec s a e ela ed o he Nb inco po a ion in o he bcc- Fe la ice and o he o ma ion o he supe sa u a ed solid solu ion. Fo longe milling In e me allics. Vol. 16. Núm. 9. 2008. Pag. 1073-1082 h p://dx.doi.o g/10.1016/j.in e me .2008.06.006 7 imes, >200 h, he XRD pa e n o Nb10 alloy shows a halo cen e ed a 2 ~ 44º and he -Fe (200) peak is educed, being unapp eciable o =400h. This is ela ed o he o ma ion o he amo phous phase in he powde pa icles. 3.2.2 Mössbaue spec ome y Mössbaue spec a along wi h he hype ine magne ic ield dis ibu ions o he di e en samples a e shown in igu es 7 and 8 o Nb10 and Nb5, espec i ely. Mössbaue spec a we e i ed using a e omagne ic si e con ibu ion wi h HF =33 T o pu e α-Fe phase (si e-F) and wo hype ine magne ic ield dis ibu ions; one o low ield con ibu ions, D1 ( om 0 o 10 T) and o he o high ield con ibu ions, D2 (>8 T). Fu he mo e, o he si e con ibu ion bu pa amagne ic wi h quad upola spli ing ~0.5 mm/s (si e-P) is necessa y o i he spec a o Nb10 o long milling imes. I is wo h men ioning ha , o such complex sys ems as he s udied he e, he e is ambigui y be ween low ield e omagne ic si es (< 5 T) and pa amagne ic ones. Fo 10 h milling, he spec a only show a sex e wi h na ow abso p ion peak (wid h ~0.30 mm/s) and hype ine magne ic ield 33 T o bo h alloys, indica ing ha he α-Fe la ice has no been signi ican ly a ec ed by milling, in ag eemen wi h EDX (he e ogeneous powde pa icles, no eally alloyed) and XRD (la ice pa ame e close o pu e α-Fe) esul s. Fo Nb10 alloy spec a a  20 h, wo new con ibu ions appea , D1 and D2. This shows he exis ence o Fe a oms in h ee di e en main en i onmen s: i s (si e- F), pu e bcc-Fe phase en i onmen ; second (D1), Nb ich en i onmen s; and hi d (D2), Fe ich en i onmen s. This la e con ibu ion can be ela ed wi h Fe a oms in he α-Fe phase bu in he p esence o impu i ies o Nb, B and/o C (due o con amina ion by he g inding media) o o Fe a oms a he in e ace egion o nanoc ys als [15]. Howe e , in he Nb5 alloy, along wi h he c ys alline con ibu ion, si e-F, only he D2 dis ibu ion is In e me allics. Vol. 16. Núm. 9. 2008. Pag. 1073-1082 h p://dx.doi.o g/10.1016/j.in e me .2008.06.006 8 obse ed (D1 is negligible). This means ha , in Nb5 alloy, Nb ich en i onmen s a e no as signi ican as in Nb10 alloy, as i would be expec ed. 4 Discussion 4.1 Simula ion o powde size e olu ion As i was p e iously men ioned, o 20 h milling, c acks a e obse ed in he pa icles su ace, which may cause he ac u e o he pa icles when he milling con inues. The change in he e olu ion end o <d> could be asc ibed o changes in he mechanical p ope ies o he sys em due o apid accumula ion o de ec s in o he pa icles [16]. This changes he balance be ween he wo p ocesses esponsible o he e olu ion o <d>: ac u e and cold welding. In ac , a quali a i e change in he mechanical beha io o he powde is clea ly obse ed o milling imes longe han 50 h. Un il 50 h milling, he powde s icks on he ial wall and ball su ace. Howe e , o longe milling imes he powde de aches om milling media su aces, no iceably inc easing he amoun o loose powde . Based on hese wo p ocesses, a basic simula ion algo i hm was pe o med o ob ain a i s app oxima ion o he endency ollowed by <d> du ing milling. The ini ial sys em consis o 500 equally sized pa icles. Once a andom pa icle is chosen, i s p obabili y o be cold welded wi h ano he pa icle is de ined by Pcw =exp(-di/dc). This exp ession depends on he size o he i pa icle, di, and a c i ical size, dc. Pa icles wi h di>dc will end o ac u e, while i di <dc, he pa icle will end o join wi h ano he . As can be in e ed om he expe imen al e olu ion o <d>, dc is no cons an du ing he milling p ocess. In ou simple simula ion, only wo di e en alues o dc we e used (suppo ed by he ab up change in he mechanical p ope ies de ec ed be ween 20 and 50 h. A dc alue 100 imes he ini ial size was used o ep oduce he apid inc ease in <d> a sho milling imes. Fo long milling imes, he cons an expe imen al alue o In e me allics. Vol. 16. Núm. 9. 2008. Pag. 1073-1082 h p://dx.doi.o g/10.1016/j.in e me .2008.06.006 9 <d> was used as dc. Simula ion esul s ep oduce he expe imen al ones a e p ope ly escaling he i e a ion s eps wi h he milling ime (see igu e 3). 4.2 Simula ion o composi ional e olu ion EDX esul s indica e ha he composi ion o pa icles is no unique, e en a long milling ime bu composi ional dis ibu ions achie e a s a iona y si ua ion. The pa ame e ΔCFe was simula ed conside ed a sys em o pa icles de ined by a 100 componen s bina y a ay, being 0 o Nb and 1 o Fe (1 % in composi ional esolu ion). Two andom pa icles will in e ac changing a po ion o hei a ays wi h he same alea o y size. The e o e, powde pa icles size and numbe emain unchanged and only composi ional e olu ion is simula ed in his e y simple simula ion. Resul s a e shown in igu e 9a along wi h expe imen al ones o compa ison. Expe imen al and simula ion esul s ag ee e en quan i a i ely (once i e a ion s eps a e con enien ly escaled), showing a s a iona y si ua ion o he sys em wi h a composi ional dis ibu ion and, he e o e, he exis ence o a ce ain deg ee o he e ogenei y (ΔCFe =18 a . % o Fe o Nb10 and 14 a . % o Fe o Nb5). O he pa ame e which enables o ollow he composi ional e olu ion is he mos p obable Fe con en in he pa icles, CFe, (shown in igu e 9b). This pa ame e apidly dec eases wi h he milling ime close o he nominal composi ion o bo h alloys. A e 20 h milling, CFe= 89 and 95 ± 2 a . % o Nb10 and Nb5, espec i ely. An inc ease wi h espec o he nominal composi ions (88 and 94 a . % o Nb10 and Nb5, espec i ely), al hough in o he expe imen al e o , would no be su p ising and could be expec ed due o Fe con amina ion om milling media. The e olu ion o CFe was also ob ained om he simple simula ion desc ibed abo e (also shown in igu e 9b, using he In e me allics. Vol. 16. Núm. 9. 2008. Pag. 1073-1082 h p://dx.doi.o g/10.1016/j.in e me .2008.06.006 16  Fo milling imes ≥50 h, he only phase p esen in he samples is a bcc Fe(Nb,B) supe sa u a ed solid solu ion o bo h alloys. A e 400 h, only o he alloy wi h he highes Nb con en , he p esence o amo phous phase is e idenced by an amo phous halo obse ed by XRD, as well as he de ec ion o an exo he mic p ocess in DSC asc ibed o c ys alliza ion. This amo phous phase is s able up o 850 K.  Fo he alloy wi h he lowes Nb con en , a e 50 h milling no new Fe a omic si es appea , being he mo e impo an con ibu ion a 33 T. Howe e , o he alloy wi h he highes Nb con en , he Fe a omic en i onmen con inuously e ol es inc easing he ac ion o pa amagne ic en i onmen s.  The Cu ie ansi ion o amo phous phase in he alloy wi h he highes Nb con en is below oom empe a u e (~250 K). This phase, de ec ed by magne iza ion measu emen o milling imes ≥200 h, was also de ec ed by X- ay di ac ion and Mössbaue spec oscopy echniques. Acknowledgmen s This wo k was suppo ed by he Spanish Go e nmen and EU FEDER (P ojec MAT 2004-04618) and by he PAI o he Regional Go e nmen o Andalucía (P ojec P06-FQM-01823). J.J.I. acknowledges a ellowship om he Spanish Minis y o Educa ion and Science. J.S.B. acknowledges a esea ch con ac om he Regional Go e nmen . Re e ences [1] C. Su yana ayana, P og. Ma e . Sci. 46 (2001) 1-184. [2] H. Glei e , P og. Ma e . Sci. 33 (1989) 223-315. In e me allics. Vol. 16. Núm. 9. 2008. Pag. 1073-1082 h p://dx.doi.o g/10.1016/j.in e me .2008.06.006 17 [3] H. Glei e , Ac a Ma e . 48 (2000) 1-29. [4] K. Suzuki, N. Ka aoka, A. Inoue, A. Makino, T. Ma sumo o, Ma e . T ans. JIM 31 (1990) 743-746. [5] A. Makino, T. Ha anai, A. Inoue and T. Ma sumo o, Ma e . Sci. Eng. A 226-228 (1997) 594-602. [6] M.E. Mc. Hen y, M.A. Willa d, D.E. Laughlin, P og. Ma e . Sci. 44 (1999) 291- 433. [7] A. He nando, M. Vázquez. T. Kulik, C. P ados, Phys. Re . B 51 (1995) 3581. [8] I. Chicinas, N. Juma e, Gh. Ma ei, J. Magn. 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Pag. 1073-1082 h p://dx.doi.o g/10.1016/j.in e me .2008.06.006 18 [19] J.Y. Yang, T.J. Zhang, K. Cui, X.G. Li, J. Zhang, J. All. Comp. 242 (1996) 153- 156. [20] J.J. Suñol, A. González, J. Sau ina, Ll. Escoda, P. B una, Ma e . Sci. Eng. A 375-377 (2004) 874-880 [21] J.S. Blázquez, V. F anco, C.F. Conde, A. Conde, In e me allics 15 (2007) 1351- 1360. [22] J. To ens-Se a, J. Rod íguez-Viejo, M.T. Cla ague a-Mo a, J. Non-C ys . Sol. 353 (2007) 842-844. [23] V. F anco, C.F. Conde, A. Conde, J. Magn. Magn. Ma e . 303 (1999) 60-62. [24] D. Oleszak, P.H. Shingu, J. Appl. Phys. 79 (1996) 2975-2980. [25] D. Hende son, J. Non-c ys . Solids 30 (1979) 301-315. [26] A. Makino, K. Suzuki, A. Inoue, T. Masumo o, Ma e . Sci. Eng. A 179-180 (1994) 127-131. In e me allics. Vol. 16. Núm. 9. 2008. Pag. 1073-1082 h p://dx.doi.o g/10.1016/j.in e me .2008.06.006 19 Figu e cap ions Figu e 1. SEM images o bo h alloys a e selec ed milling imes. Figu e 2. a) SE image, b) BSE image o a ypical pa icle o Nb10 alloy a e 2 h milling and c) EDX spec a o selec ed poin s indica ed in a). Figu e 3. Expe imen al and simula ed da a o he a e age powde pa icles size as a unc ion o he milling ime o bo h alloys. Figu e 4. His og ams o he pe cen age o Fe con en in o al Fe+Nb con en o bo h alloys a selec ed milling imes. Figu e 5. C con en as a unc ion o milling ime o bo h alloys. The slopes o he di e en i ed lines a e also indica ed. Figu e 6. XRD pa e ns o bo h alloys a e selec ed milling imes. Figu e 7. Mössbaue spec a and hype ine magne ic ield dis ibu ions o Nb10 alloy a e selec ed milling imes. Figu e 8. Mössbaue spec a and hype ine magne ic ield dis ibu ions o Nb5 alloy a e selec ed milling imes. Figu e 9. Expe imen al and simula ed alues o a) ΔCFe and b) CFe as a unc ion o he milling ime (expe imen al) and i e a ion s eps (simula ion). Ho izon al lines a 88 and 94 a .% Fe co espond o he nominal alues o Nb10 and Nb5, espec i ely. I e a ion s eps axes ha e been con enien ly escaled o show he ag eemen wi h he expe imen al da a. Figu e 10. a) La ice pa ame e , b) minimum c ys al size and c) maximum mic os ain as a unc ion o milling ime o bo h alloys. Figu e 11. A ea ac ion o he di e en Mössbaue con ibu ions o he o al i ing as a unc ion o milling ime o bo h alloys. In e me allics. Vol. 16. Núm. 9. 2008. Pag. 1073-1082 h p://dx.doi.o g/10.1016/j.in e me .2008.06.006 20 Figu e 12. Magne iza ion cu es as a unc ion o empe a u e o Nb10 alloy a e 100, 200, 300 and 400 h milling. Figu e 13. DSC scans a 40 K/min o bo h alloys a e selec ed milling imes. Symbols a e supe imposed o e he cu es o dis inguish hem. Figu e 14. XRD pa e ns o Nb5 alloy a e di e en hea ed empe a u es. Figu e 15. XRD pa e ns o Nb10 alloy a e di e en hea ed empe a u es. Figu e 16. Mössbaue spec a and hype ine magne ic ield dis ibu ion o Nb5 alloy a e annealed ea men . Figu e 17. Mössbaue spec a and hype ine magne ic ield dis ibu ion o Nb10 alloy a e annealed ea men . In e me allics. Vol. 16. Núm. 9. 2008. Pag. 1073-1082 h p://dx.doi.o g/10.1016/j.in e me .2008.06.006 21 Figu e 1 2 h 500  m 20 h 500  m 200  m 100 h 100  m 400 h Nb10 500  m 2 h 20 h 500  m 100  m 100 h 50  m 400 h Nb5 In e me allics. Vol. 16. Núm. 9. 2008. Pag. 1073-1082 h p://dx.doi.o g/10.1016/j.in e me .2008.06.006 22 Figu e 2 50 m A B C B Fe. Nb 0 2 keV c ) a ) b) Fe. Nb In e me allics. Vol. 16. Núm. 9. 2008. Pag. 1073-1082 h p://dx.doi.o g/10.1016/j.in e me .2008.06.006 23 Figu e 3 0 100 200 300 400 0 100 200 300 Nb10 Nb5 i e a ion s ep (x103) <d> [m] milling ime [h] 0 5 10 15 20 25 30 35 simula ed In e me allics. Vol. 16. Núm. 9. 2008. Pag. 1073-1082 h p://dx.doi.o g/10.1016/j.in e me .2008.06.006 24 Figu e 4 4 8 12 2 4 6 2 4 2 4 6 Nb10 0.2 0.4 0.6 0.8 1.0 2 4 % Fe 4 8 12 Nb5 2 h 4 8 10 h 2 4 6 20 h 4 8 12 50 h 0.2 0.4 0.6 0.8 1.0 4 8 400 h % Fe In e me allics. Vol. 16. Núm. 9. 2008. Pag. 1073-1082 h p://dx.doi.o g/10.1016/j.in e me .2008.06.006 25 Figu e 5 0 100 200 300 400 0.0 0.6 1.2 1.8 C [%] milling ime [h] N5B N10B (7 ±2)*10-4 a . % C /h (3.6±0.3)*10-3 a . % C /h In e me allics. Vol. 16. Núm. 9. 2008. Pag. 1073-1082 h p://dx.doi.o g/10.1016/j.in e me .2008.06.006 32 Figu e 12 100 200 300 400 0 30 60 90 120 400 h 300 h 200 h 100 h M 0 [emu/g] T [K] In e me allics. Vol. 16. Núm. 9. 2008. Pag. 1073-1082 h p://dx.doi.o g/10.1016/j.in e me .2008.06.006 33 Figu e 13 400 500 600 700 800 900 1000 empe a u e [K] 400 h 400 h 50 h 50 h 20 h 20 h 5 h 5 h Nb10 Nb5 0.2 W/g (exo) dH/d In e me allics. Vol. 16. Núm. 9. 2008. Pag. 1073-1082 h p://dx.doi.o g/10.1016/j.in e me .2008.06.006 34 Figu e 14 40 50 60 600 K 800 K as-milled 2  [deg ee] 1000 K 500 1000 0,286 0,288 T [K] a [nm] In e me allics. Vol. 16. Núm. 9. 2008. Pag. 1073-1082 h p://dx.doi.o g/10.1016/j.in e me .2008.06.006 35 Figu e 15 40 50 60 600 K 800 K as-milled 2  [deg ee] 1000 K 500 1000 0 50 100 T [K] X C [%] In e me allics. Vol. 16. Núm. 9. 2008. Pag. 1073-1082 h p://dx.doi.o g/10.1016/j.in e me .2008.06.006 36 Figu e 16 0,1 0,2 0,08 0,16 0,24 0,2 0,4 -8 -6 -4 -2 0 2 4 6 8 0 5 10 15 20 25 30 35 0,2 0,4 0,6 as-milled 600 K ela i e ansmi ion p obabili y 800 K eloc y [mm/s] B hyp [T] 1000 K In e me allics. Vol. 16. Núm. 9. 2008. Pag. 1073-1082 h p://dx.doi.o g/10.1016/j.in e me .2008.06.006 37 Figu e 17 0,1 0,2 -8 -6 -4 -2 0 2 4 6 8 0,1 0,2 0,03 0,06 0 5 10 15 20 25 30 35 0,1 as-milled p obabili y eloci y [mm/s] ela i e ansmi ion 600 K 800 K B hyp [T] 1000 K