Issue 14

V.

Di Cocco et alii,

Frattura ed Inte

grità Strutturale

, 14 (2010) 52

-63; DOI: 10.322

1/IGF-ESIS.14.06

Mic per (0.1 Ben inv equ dam

rostructure forming scan N – 15 s). ding tests w estigated con al to 35 mm aging mech tallographica ined as crack ermetallic pha ig. 3 sho intermet eutectic ain “multilay higher than rostructure, lies an evide ng pure Zn ferent growth ition implies PERIMENT

analysis was ning electro ere perform dition. An e , that corre anisms for lly prepared s number/co ses growth kin ws binary Zn allic phases a transformatio er” coatings the Sn con but only flui nt influence baths are ch kinetic, wi a decrease fo AL RESULTS

performed n microscop ed by means lectromecha sponds to a each investig and observed ating length etics -Fe and Zn nd the secon n correspon with the “cla tents used in difies the ba on the phase aracterized b th linear beh r the import

by means o e (SEM) ana of a non-st nical 100kN bending an ated loading by means o [12-14].

f traditional lysis, with E andard devic testing mac gle equal to condition, f a LOM. D

metallograp DS. Vickers e (Fig. 2a) a hine was use 30° (Fig. 2c longitudinal amage level w

hic techniqu microhardne nd repeated d, consideri ) [7-11]. Fin sections of as evaluated

es (LOM ob ss tests were at least thre ng a crosshe ally, in orde the bended in term of

servations) also perform e times for e ad displacem r to identify specimens w “cracks dens

and ed ach ent the ere ity”,

me def

E X

Int usi dif add F obt one mic imp

-Sn phase dia d does not s ding to very ssical” interm industrial a th. Focusing thickness-tim y a parabolic aviour in w ance of ζ pha

grams. The how interme high Sn cont etallic phase pplications, i the interme e curves, es diffusion c hich growth se with respe

first is chara tallic phases ents. Both pu s. Considerin t implies tha tallic growth pecially cons ontrolled gro is interface ct to the oth

cterized by th and is charac re Zn and Z g that a cont t Sn additio kinetics (Fig idering η and wth (Fig. 4a controlled [ er intermetal

e presence o terized by th n + 3 %wt S ent of 3% of n do not mo . 4), investig ζ phases. C ). The Sn ad 2], Fig. 4b. F lic phases (Fi

f the “classi e presence o n baths allow Sn is a facto dify the coa ated Sn con oatings obtai dition impli urthermore, g. 4a and 4b)

cal” f an to r of ting tent ned es a Sn .

1700

450

1500

L

L

400

1300

350

1100

(  Fe)

300

L+ 

900

(  Fe) p

250

Temperature [°C]

Temperature [°C]

700



(  Fe) f

 

200

500

(βSn)→



(  )→





150



300

0 10 20 30 40

50 60 70 80

90 100

0 10 20 30 4

(a) gure 3 : Phase 0 50 60 70 80 Zn[wt%]

90 100

Sn[wt%]

(b)

Fi

diagrams. (a) Z

n-Fe; (b) Zn-

Sn.

Coating

Coating

  

 



40

0

400

300

30

0

100 Thickness [  m] 200

10 Thickness [  m] 0 0 20

0

0

0 200 40 T

(a) intermetallic p 0 600 800 ime [s]

1000

(b) b) Zn + 3 %w 400 600 8 Time [s]

00 1000

0 200

hases kinetics

. (a) Zn bath; (

t Sn bath.

Coatings and

Figure 4 :

54