Issue 14

D. Firrao et tructure; (iii) ith the overp perature att front inciden ation on mec tigate these k ng n slip and m e one that pr hereafter indi ncreases upo ation rates aluminium a fluenced by e temperatu tter of fact, i ounced in all r stress rema has to note view, so tha 31 [4], even ritical comp Sixties, it wa Pa for copp nd 100 MPa f comparison for pure iro or mechanic ion tests, me fault energy, ith the defo gards Cr-Ni range betwe 5 to 10 mJ/m lues will def Tab. 1 * . On brass plastic s. peratures an . common o he respective

alii, Frattura ed complete r ressure wave enuation insi ce point. hanical twin inds of defo echanical tw edominates i cated as  c,slip n lowering t (10 -5  10 -1 s -1 ) lloys, with th composition re (it increas n close-pack oys, as stainl rkably increa that the exis t Schmidt’s before the e onent for me s possible to er, 55-90 MP in silver-gold , values from n at 15 K. al twinning, chanical twin  sf , and incre rmation rate stainless stee en 400 and 2 2 passing fro orm mainly b the contrary, ally deforms d very high d bjects under Hall-Petch t

Integrità Strutt ecrystallizatio being still a de the mater s and multip rmation mec inning is rul n objects exp , has values i he temperatu , maximum v e minimum variations (e es for decrea ed metals the ess steels. Th ses. tence of a c law, which a xistence of d chanical twin suggest som a for Cu-8.9 alloys [5], w 5 to 35 MP hereafter ind s appear only ases as the la and it seem l, there is a d 00 K [8, 9, m 300 to 20 y slip. This b additions of by twinning eformation going explo ype relations

urale, 14 (2010) n with a to ctive, newly ial, recrystall le slip bands hanisms [3]. ed by the re osed to a de n the vicinity re or increa alues for  c,s ones being on ven small tr sing tempera increase of e deformatio ritical compo llows to dete islocation w ning deform e values for % Al alloys, ith data rang a have been icated as  c, at higher ap tter increases s to mildly ecrease of  s 10]. In partic 0 K. ehaviour is o alloying elem easier than C rates mechan sions, the co hips [11, 12]

81-92; DOI: 10 tally fine str formed cryst ization phen in FCC meta spective valu tonation fron of 10 -4  10 -5 sing the defo lip vary from e order of m aces of forei tures) mostly  with 1/T i n rate has a nent of shea rmine the lo ere postulate ation existed critical twinn 300 MPa fo ing from 75 suggested fo , has usua plied stresses . decrease up f values betw ular, for a st twin bserved in A ents causing u, because th ical twinning mpetition b , namely

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14.09

gra rec If c twi evi Du exp Cry In res Th the roo to 4 Th inc less me wh As kno wit han at t Th val  c,tw Co tem mJ 16% Me sho fac to C It c def In def val for the 13

in boundarie rystallization omplete recr nning or mu dent in zones e to the lack losion, it can stal deformat single crystal olved shear s e critical reso elastic shear m temperatu MPa for co e critical she rease its valu in the FCC tals (almost n en d  /dt incr it regards m wn early fr h crystals ori d, debate to he end of th ues are listed silver, 100 M alloys at 75% MPa for tin us, the critic ues than  c,slip in is mainly i ntrary to  c,s perature as d /m 2 per ever Cr and 13% tals and meta w the highes ilitate twinnin u lowers  sf an be conclu ormation me polycrystals, ormation me  y =  f known form  y,tw =  ived for twin s

s) with a du and grain gro ystallization ltiple slip. D closer to the of well orga be useful to ion mode: slip s the compe tresses, the lo lved shear st modulus;  c res and quas pper alloys an ar stress  c,sli e); it is also and HCP on ull in Al) an eases, the slip echanical tw om an histor entation date decide wheth e Fifties, beg afterwards: Pa for gold, Au [6]. Fo and from 210 al resolved s . In fact, in c nfluenced by lip ,  c,twin doe oes  sf [7]. I y temperatur Ni,  sf chan l alloys havin t  sf values a g deformatio as its percen ded that on chanism in s which usua chanisms is g (d -1/2 ) ula for slip a + k s

al grained s wth. is attained w ue to the tem detonation nised inform further inves versus twinni tition betwee wer being th ress for slip, ,slip strongly i istatic deform d 3 MPa for p is highly in affected by th es. As a ma d more pron critical shea inning, one ical point of s back to 19 er a similar c inning of the about 150 M between 50 a r the sake o to 300 MPa hear stress f ommon tens the stacking s not vary w n fact, as it re e degree in a ges from 14. g high  sf va s reported in n: a 30% Zn tage increase ly at low tem ingle crystals lly compose overned by t

ucture; (iv) t als may unde omena are m ls undergon

otal rgo ore e an

es of the cri t. G, with G b rmation rate 8 MPa for st agnitude low gn atoms hi in BCC me s limited in p similar influe ad to be app d. On the o lasted long; o ing stress. Th r nickel, 50 M and 100 MPa r zinc, from lly much hig than slip ba on lowering een 0.05 and ainless steel w l and Ni, wh a decrease o e addition of is the favou etween the r stress,  c ,

tical

eing . At eels er. ghly tals, ure nce; was lied ther nly ose Pa for 4 to her nds. the 0.1 ith ich f  sf Zn red two

(1)

the

nd /2 )

+ k tw

(d -1

(2)

ftw

der

ning.

* Va

lues of  sf

may

differ from th

ose reported

in the Tab. 1 i

f measuremen

ts taken by oth

er authors are

taken into acc

ount.

85