Materials Science and Engineering A 527 (2010) 18611868

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Materials Science and Engineering A

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Characterization of Ti6Al4V open cellular foammanufa

L.E. Murr . MB.I. Macha Department o X 799b W.M. Keck Cec Department o

a r t i c l

Article history:Received 17 SeReceived in reAccepted 5 No

Keywords:Electron beamOpen cellularElastic moduluOptical microscopySEM and TEM characterization

abricfrom

bricatrengter forrelatn cellpinglular

biomedical, aeronautics, and automotive applications. 2009 Elsevier B.V. All rights reserved.

1. Introdu

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melt-processing of aluminum and aluminum alloysed cellular foams with open or closed cells for at leastes [15], these same highly-porous metal or alloyve only recently been fabricated for Ti6Al4V [6,7].w melting point and low reactivity of aluminum alloys-state processing possible, the high melting points andemical afnity of titanium and its alloys with oxygenn as well as their extremely high reactivity with mostials has prevented cellular foam processing from these

alloy foams have numerous potential applicationsuence of their light weight and exceptional, isotropicproperties, and corrosion resistance. These include actural applications in aerospace, aeronautics and auto-tems which take advantage of density-compensatedd stiffness at elevated temperatures. Murr et al. [7]ecently demonstrated that Ti6Al4V cellular foamsy additive manufacturing (AM) using electron beam

ding author at: Department of Metallurgical and Materials Engineer-rsity of Texas at El Paso, 500 W. Univrsity Ave., Room M-201, El Paso,0, USA. Tel.: +1 915 747 5468; fax: +1 915 747 8036.ress: lemurr@utep.edu (L.E. Murr).

melting (EBM) of precursor powder can have innovative applica-tions as the next generation biomedical implants. These cellularfoams were fabricated by EBM using CAD models created from CT-scans of aluminum alloy foams. The CAD models serve as buildingunits or building elements which allow spatial replication similarto crystal unit cells [7].

The present paper is an extension of this preliminary research[7] on the fabrication of Ti6Al4V cellular foams using EBM.We measured the stiffness (or Youngs modulus) and examinedthe stiffness versus density in contrast to many very low den-sity foams (with relative density

1862 L.E. Murr et al. / Materials Science and Engineering A 527 (2010) 18611868

Fig. 1. Softwavolume (isomeFrom Murr et

illustrates 3systems toEBMsystempowder (ha0.13% O (ba30m) isby rapid scmelt scan iselectivelyCAD systemment or str(designated(Fig. 1(c) anre (CAD) models for open cellular foams based upon micro-CT-scans for aluminum alloytric view); (c) 3X base foam; (d) 3X test foam volume. In (b) the virtual volume is denote

al. [7].

D foam models which are created from these softwaredirect the layer-melt scan in the EBM. The ARCAM A2,hasbeendescribed indetail elsewhere [7,8]. Ti6Al4Vving a nominal composition of 6.04% Al, 4.05% V andlance Ti in wt%) and an average particle diameter ofraked into 100m thick layers which are preheatedanning of the beam followed by a melt scan [7,8]. Thes driven by the computer-aided (CAD) system whichmelts each additive layer to build the 3D structure. The

incorporates the CT scan in the form of a prime ele-uctural element. Fig. 1 utilizes the prime foam elementIX) to produce models for 2X (Fig. 1(a) and (b)) and 3Xd (d)) foams. Foams were also built from 2.5X and 4X as

well as illusa cellular fothe surfaceand (c) thestudy we faament strustructures.rently has fvolume supalready beecreation ofshown scheMagics, RPTfoams (a) 2X base foam or primary build unit (1X). (b) 2X test foamd by dotted lines.

trated in Fig. 2. Fig. 2 shows a CAD model slice througham build illustrating cell structure features implicit inview in Fig. 1 (arrow in Fig. 1(c)). In Figs. 1 and 2(a)se cell structure ligaments are solid. However, in thisbricated open cellular foams with solid (S) cell or lig-ctures (arrow in Fig. 1(c)) as well as hollow (H) cellThese are illustrated in Fig. 2(b). The EBM system cur-our buildingmodules: preheat,melt, wafer support, andport. The beam conditions for preheat and melt haven described. The wafer system module allows for thethe open contours during the open cell foam fabricationmatically in Fig. 2(b). The wafer supports are created inM software as 3D objects without a specic thickness.

L.E. Murr et al. / Materials Science and Engineering A 527 (2010) 18611868 1863

Fig. 2. CAD mo1X, 2X, 2.5X, 3to the most de(b) Enlarged ce(c) The three i3X) at reduced

Consequentdesired comhollow ligadiameter. Tsame for allstructures wture cellulawere also inthese struct

Murr etresidual milated meshfor thin strby EBM. Thdesirable bharder (andwas assumecell or ligamstructures (to create stdiscs) froma test structand compotest arraysTEM discs cthis simulaEBM-test stto simulatecontinuoustions in hea

The elaslular foamsfrequency aGenk, Belgi

impulse-excitation using a small mechanical tapping device to cre-ate a mechanically induced vibration in the cellular foam sample[9]. This vibration consists of the sum of several resonant frequen-cies, fr, each of which dampens according to the energy absorption

matee for

f 2r

isassstrust tooftevencellued toby epo

lasticed, pd me100

ed aH2O

m theld

ecimanded i

0 TEMmet

ults

3 illuby E

a) shdel sections (2.3 cm2.3 cm) for the open cellular Ti6Al4V foams:X and 4X. (a) The least dense (or most porous) foam (4X) in contrastnse (or least porous) foam (1X). 1X represents the base CAD element.ll wall or ligament in 4X (a) having a solid (S) or hollow (H) structure.ntermediate cellular foam sections for solid cell structures (2X, 2.5X,magnication relative to (a).

ly, this module only melts the contour (Fig. 2(b)) of theponent area when used as a model, and only builds a

ment shell with a wall thickness of roughly one beamhis means that the shell thickness will be roughly thefoams (1X to 4X in Fig. 2). These complex, hollow cellere functionally lower in density than the solid struc-

of theE, in th

E = m

whereimen mnon-decontraThis isthe con

Thedesignby Ashsize orafter emounttion anusing amount100mLcut froS-4800ent spblocksdescribH-800a gonio

3. Res

Fig.ricatedFig. 3(r foams with identical porosity or pores/inch (ppi). Weterested in comparing the corresponding stiffnesses forural variants.al. [7] have already noted that the microstructures andcroindentation hardnesses were different for reticu-structures because of the variations in cooling ratesuts versus larger, solid, monolithic components builtese variations were observed to be circumstantiallyecause the thinner strut geometries were up to 20%stronger) than solid monoliths [7]. Consequently, it

d that in the fabricated cellular foams, those with solident structures would differ from the hollow or open

Fig. 2(b)) in a similar fashion. Since it was not possibleandard, electron transparent thin sections (from 3mmcellular foam ligament structures (Fig. 1), we devisedure to simulate cooling variations for thin componentsnent arrangements implicit in Figs. 1 and 2(b). Thesewere thin-plate structures from which standard 3mmould be punched from one of the test strips composingted, thin ligament or connecting cell structure. Theseructures could be altered in structure and dimensionsthe foamcell dimensions implicit in Fig. 1. Connected orplate arrays and unconnected arrays allowed for varia-t conduction and altered the solidication rate.tic (Youngs) moduli for EBM fabricated Ti6Al4V cel-were initially measured in this study using a resonantnd damping analyzer (RFDA) developed by IMCE, n.v.um [9]. This non-destructive testing system is based on

foams in boconnectingillustrates cture at theillustrates tstructuresthicknessesconstant anmarizes thewith their msity (), releffective ponal cell poraverage celfoams (tS) acell structualong withaverages. Whollow) celTable 1 havwith most oaluminum a

As impliboth the somicroindengreater thadentation hranging frorial to produce a measurement of the elastic modulus,m:

(1)

a geometrical (specimen) shape factor, m is the spec-, and fr is the prominent, resonant frequency [9]. Thisctive testing measures the dynamic Youngs modulus inthe static modulus for tensile or compression testing.n referred to as a stiffness-related number rather thantional Youngs modulus.lar foams fabricated as test samples in this study weresatisfy the general metal foam requirements discussedt al. [1]: height/width >1.5, height >7 times the cellre (channel) size. Fabricated test components were,modulus measurements, sliced in sections which wereolished, and etched for opticalmetallographic examina-asurement of Vickers microindentation hardness (HV)gf (1N) load for a 10 s dwell time. The etching of thend polished sections involved a solution consisting of, 2.5mL HF and 5mL HNO3. Representative sections

e cellular mesh samples were also observed in a Hitachiemission SEM operating at 20kV. Electron transpar-

ens prepared from solid, full density (4.3 g/cm3) testthe test/simulation congurations described above, andn detail by Murr et al. [8], were observed in a Hitachi

operating at 200kV accelerating potential, employinger-tilt stage.

and discussion

strates examples of thevedifferent cellular foams fab-BM utilizing CAD models illustrated typically in Fig. 1.ows the 1X, solid cell, base element foam and the 4Xth the solid cell (S) hollow cell (H) wall structures (orligaments) shown schematically in Fig. 2(b). Fig. 3(b)ross-sectional (optical) views for the 3X solid cell struc-left and the 4X open cell structure at the right. Fig. 3(c)he corresponding solid (S) and hollow (H) cell ligamentand the nominal designations for the cell or cell wall: tS and tO, respectively. Note that tO will be essentiallyd related to the electron beam diameter. Table 1 sum-solid andopen (or hollow) cell foams in this study alongeasured pore density (pores/inch, ppi), measured den-ative density (/o) (where o is 4.3 g/cm3), and therosity in percent, which includes the nominal, inter-osity for the open cell structures. Table 1 also lists thel structure (ligament) thickness for the solid cellularnd the average cell wall thickness (tO) for the hollow

res for the open cellular foams (as illustrated in Fig. 3(c))the corresponding Vickers microindentation hardnessith the exception of the most dense solid and open (or

l structures, the experimental hollow cellular foams ine relative densities equal to or less than 0.3, consistentf the other reported metal and alloy foams, especiallynd aluminum alloys [1,2].cit in Table 1, the cell ligament or wall structures forlid cell structures and the hollow cell structures exhibittation hardnesses which vary from roughly 29% to 37%n monolithic, bulk samples where the Vickers microin-ardness is nominally 3.5GPa. This in contrast to valuesm 4.5 to 4.8GPa for the thin ligaments or hollow cell

1864 L.E. Murr et al. / Materials Science and Engineering A 527 (2010) 18611868

Fig. 3. Compacross-section vthickness desi

walls. Thisdimensionsligament thtation hardFig. 3(c)).rison of 1X solid and 4X solid and open cell structure Ti6Al4V foams (a). (b) A solid ceiews. (c) Enlarged, schematic views for cell ligaments or walls in (b) showing solid cell wgnation (tO) corresponding to the foam cross-sections in (b).

results by rapid solidication facilitated by the small. It can be observed in Table 1 that the larger, solidickness exhibits consistently lower (7%) microinden-ness in contrast to the hollow cell wall thickness (tO in

Fig. 4 coten), -phahardness oa hollow cmicrostructll structure 3X foam (left) and an open cell structure 4X foam (right)all structure thickness designation (tS) and hollow cell structure wall

mpares a solid, monolithic build acicular (Widmanstt-se grain structure having a Vickers microindentationf 3.6GPa (Fig. 4(a)) with a 2.5X cellular foam withell structure exhibiting predominantly -martensiteure, having a Vickers microindentation hardness of

L.E. Murr et al. / Materials Science and Engineering A 527 (2010) 18611868 1865

Table

1Ti

6Al

4Vce

llula

rfo

ampro

per

ties

.

Foam

CAD

des

ignat

ion

*Po

reden

sity

(ppi)

aSa

mple

mas

s,m

(g)

Den

sity

(g

/cm

3)b

Rel

ativ

eden

sity

(/

o)c

Poro

sity

(%)

Cel

lwal

lorliga

men

tth

ickn

ess(m

m)d

Cel

l(w

all)

har

dnes

s(G

Pa)e

Res

onan

tfreq

uen

cy,

f r(k

Hz)

Stiffn

essE

(GPa

)Rel

ativ

est

iffn

ess

(E/E

O)f

(10

3)

1X-s

olid

(S)

1141

.21.

990.

4555

0.9

4.6

23.3

9.97

90.0

2X-s

olid

(S)

726

.91.

290.

2971

1.2

4.7

14.6

2.55

23.2

2.5X

-sol

id(S

)6

19.3

0.93

0.21

791.

44.

613

.91.

6515

.03X

-sol

id(S

)4

16.6

0.80

0.18

821.

64.

110

.60.

908.

24X

-sol

id(S

)3

16.1

0.78

0.18

821.

94.

610

.60.

756.

8

1X-h

ollo

w(H

)11

41.2

1.99

0.45

550.

54.

522

.99.

7788

.82X

-hol

low

(H)

717

.20.

830.

1981

0.5

4.7

9.4

0.48

4.4

2.5X

-hol

low

(H)

614

.10.

680.

1585

0.5

4.6

14.4

1.35

12.3

3X-h

ollo

w(H

)4

12.1

0.58

0.13

870.

44.

912

.91.

2911

.74X

-hol

low

(H)

39.

70.

470.

1189

0.4

4.8

10.5

0.48

4.4

*Bas

edupon

thedes

ign

(CAD)fe

ature

snot

edin

Figs

.2an

d3.

aPo

res/

inch

(ppi).

bBas

edupon

axe

d,f

abrica

ted

virtual

volu

meof

20.7

4cm

3:fo

rdim

ension

sof

2.3cm

2.

3cm

3.

6cm

.c

o=4.

43g/

cm3.

dTh

eth

ickn

essfo

rth

eso

lid

cellsis

t S(a

ve.)

whilefo

rth

eop

ence

llsit

ist O

(Fig

.3(c

)).t

Ow

illb

ees

sential

lyco

nst

antas

not

edsince

itre

pre

sents

theel

ectron

beam

dia

met

eras

direc

ted

byth

ew

afer

suppor

tm

odule

discu

ssed

earlie

r.e

Not

eth

atth

enom

inal

,res

idual

yiel

dst

rengt

hca

nbe

estim

ated

asH

V/3

wher

eHV

isth

eVicke

rsm

icro

inden

tation

har

dnes

s.fE O

=11

0GPa

.

Fig. 4. Compacomponent (aa wall thickneshown in (a).

4.5GPa. Co4X foam wmicroindentively. Thecell wall stsolid sectiowhere renstrength ansince the ya third of th[10]. Fig. 4phase; primis characte(Fig. 3(c)).

Fig. 5 coto Fig. 4(a)phase (dathe microintrast, Fig. 5(a thin (1.11 cm1 cmhardness fopares the somuch nergrains, all c

Fig. 6(a)build microseparatedbrative opticalmetallograph images for a solid (fully dense)monolithic) and a 2.5X, open cell structure foam (b). The image in (b) representsss region illustrated at tO in Fig. 3(c). The magnication is the same as

rrespondingly, comparing the solid cell wall structureith the hollow cell wall structure 4X foam producedtation hardness values of 4.6GPa and 4.8GPa, respec-microindentation hardness of 4.6GPa for the solidructure in contrast to 3.6GPa for Fig. 4(a) for a bulkn is characteristic for microstructure strengtheninged (or smaller dimension)microstructures implyhigherd associated microindentation hardness, especially

ield stress (Y) for many metals and alloys is roughlye Vickers microindentation hardness (HV): Y =HV/3

(b) shows a mixture of -martensite and the hcp -arily -martensite. The microstructure in Fig. 4(b)

ristic of thin wall structures in hollow cell ligaments

mpares a section from a solid monolithic build similarexhibiting acicular -plates with continuous, inter-rk). Consistent with solid monolithic builds (Fig. 4(a)),dentation hardness in Fig. 5(a) was 3.5GPa. In con-b) shows the corresponding, rened microstructure formm thick) strip from a test model or simulated buildon a side. In contrast to Fig. 5(a), the microindentationr Fig. 5(b)was 4.8GPa, an increase of 37%. Fig. 5(a), com-fter, solid monolithic, acicular -grain structure with amixture of , -martensite, and particulated -phaseontributing to increased hardness (and strength).showsabright-eld TEM image for the solid,monolithicstructure in Fig. 5(a) consisting of acicular -plateletsynarrow, interphase regions of-phase, spaced2m.

1866 L.E. Murr et al. / Materials Science and Engineering A 527 (2010) 18611868

Fig. 5. OpticaEBM fabricatein Fig. 4 showiin contrast tosame as show

In comparisponding toparticulatioin Fig. 6(b)Fig. 6(a). Thmicrostruct

Fig. 7(a)sus the relato the solidsomewhatof open celson [11], anmaterials [2

E

Eo=(

o

)

where n=2that n varieTi6Al4V omeasured fo[7]. It can bt for the h

Fig. 7(b)Youngs moporosity, cosured ultracurve ttedever, unlikel micrographs showing acicular -phase microstructure for a solid,d Ti6Al4V cylinder (a) and a 1.1mm thick strip in a test element asng rened- and-phase (dark dots). The hardness in (a)was 3.5GPa(b) where the hardness was 4.8GPa. The magnication in (b) was then in (a).

son, Fig. 6(b) shows the TEM microstructure corre-a 1.1mm thick test strip represented in Fig. 5(b). The

n of -phase grains implicit in Fig. 5(b) is illustratedwhere the interphase spacing is roughly half that inese features are characteristic of the 2.5X solid cell wallure illustrated in Fig. 4(b).shows a loglog plot of the relative stiffness values ver-tive density values listed in Table 1. The straight-line t(S) cell wall structure data points has a slope of 2.4,

higher than the value of 2 tted for a large numberlular aluminum foam results as summarized by Gib-d implicit in the GibsonAshby model for open cellular]:n

(2)

generally. However, experimentally it has been showns from about 1.8 to 2.2 [1]. In our earlier work involvingpen cellular mesh structures, a value of n=2.4 was alsor a simple cubicmesh element array fabricated by EBM

e noted in Fig. 7(a) that there is no similar straight-lineollow cell wall (H) foam structures.illustrates that the measured stiffness (the elastic ordulus (E)) values were found to vary inversely withnsistent with literature values for various foams mea-sonically and in compression testing, especially theto the solid cell wall structure foams (S) [12,13]. How-these literature values, the pore fraction or porosity is

Fig. 6. TEM bcorresponding-platelets w1.1mm test pFig. 9(b) illustpattern insertinsert in (b) sNote the magn

>50% (in Fig50% [13]. Thwere, howe55% porositwhich exteE approachfor the hollbe measurein Table 1also be notedensity (pp

The compredicted u

o= C

(

o

where anTi6Al4V,but ranging0.2% offsetright-eld images corresponding to optical microscope images formicrostructures in Fig. 9. (a) Solid monolith exhibiting 2m wide

ith -phase boundaries. Arrow denotes an / grain boundary. (b)late (Fig. 4) electropolished disc. The TEM image corresponds torating rened (dark). The selected area electron diffraction (SAED)in (a) shows the -phase (h c p) (0 01) plane while the SAED patternhows additional, multiple diffraction spots from the rene -phase.ication of (a) and (b) is the same.

. 7(b)) while the literature values are between 2% ande stiffness values at 50% porosity for literature valuesver, observed to be 15GPa; extrapolated to 5GPa aty. This is consistent with the data plotted in Fig. 7(b)nds the E versus porosity values to 90% porosity, withing zero at 95% porosity. Note that because the porosityow cell wall structure (H) foams in Table 1 could notd by Archimedes method, the porosities for all foamswere calculated from the densities: ( o)/o. It cand in Table 1 that E values also vary inversely with porei).pressive strength of open cellularmetallic foams can besing the GibsonAshby model:)3/2

(3)

d o denote the strength of the porous and fully denserespectively, and C is a scaling factor, typically near 0.3,from 0.1 to 1 [1]. Typical values of o, the residual

yield stress for Ti6Al4V EBM components has ranged

L.E. Murr et al. / Materials Science and Engineering A 527 (2010) 18611868 1867

Fig. 7. (a) Relative stiffness plotted against relative density for experimental solid cell wall (S) and hollow cell wall (H) Ti6Al4V cellular foams. The solid line is tted tothe solid cell (S) foam data. (b) Stiffness (Youngs modulus) versus porosity for solid cell wall (S) and hollow cell wall (H) Ti6Al4V foams. The solid line is tted to the solidcell (S) foam data.

Fig. 8. EBM CAD model half-section (a) and corresponding, fabricated monolithicfoam component (b) which was cut to show the half-section view.

from1.1GPfor o and Table 1 varfoams (S), a(H). Conseq36.9 for thefactor of 3.8lower porosfor the EBM

The versfunctional Tis unpreced

Fig. 9. ExampEBM.a to1.3GPa [8,14]. Assuming anaverage valueof 1.2GPa=HV/3, relative strengths for the Ti6Al4V foams in

y from 1.14 to 1.25 for the solid cell wall structurend 1.25 to 1.36 for the hollow cell structure foamsuently, the scaling factor, C, in Eq. (3) varies from 3.8 tosolid and open cell structure foams listed in Table 1, a36.9 larger than conventional aluminum foamshavingities (

1868 L.E. Murr et al. / Materials Science and Engineering A 527 (2010) 18611868

lattice structures fabricated by Cansizoglu et al. [6], and foamsproduced in this work, have not been fabricated by any otherprocess. Figs. 8 and 9 illustrate a few examples of complex foamstructures which can be fabricated as monolithic components. Thecross-section model in Fig. 8(a) along with an EBM fabricatedmonolithshown in Fig. 8(b) can serve as an example for nextgenerationorthopaedic component fabricationwhere cortical bonestiffness and density are matched with the outer foam structureand the less dense inner foam is characteristic of trabecular bone[7]. The foam structures in Fig. 8(b) are also joined to a solid endform to create a complex monolithic product which cannot befabricated by any known process other than additive manufactur-ing.

Finally, Fig. 9 illustrates the ability to scale Ti6Al4V foamstructures relative to the test components illustrated in Fig. 3(a)above. Because foam structures are generally isotropic and energyabsorbing, Ti6Al4V foams will have innovative aeronautical andautomotive applications implicit in Figs. 8 and 9. However, additivemanufacturing often leads to non-isotropic mechanical proper-ties. Nonetheless, we have not observed any directionally differentmicrostructural features. This issue will be experimentally exam-ined in future studies.

4. Summa

The abiliEBM as dema unique inturing procmoduli forsity (especiwith the Gvaries invererature valualuminum [

In thising both socomplex stbulk or solmote -moften intermmicrostructligaments,tures, promstrength. Intures in con40%.

It has been shown that complex foam structures can be fabri-catedwith solid, fullydensemonolithsbyEBM.While this studyhasdemonstrated innovative Ti6Al4V open cellular foams and com-plex, multifunctional component fabrication having a wide rangeof technology applications, the implications are that any metal oralloy system, or complex array which can be modeled in digitalCAD, can be fabricated by additive manufacturing using EBM witha suitable precursor powder.

Acknowledgements

This research has been supported in part by Mr. and Mrs. Mac-Intosh Murchison Endowments at The University of Texas at ElPaso. A portion of this research was also supported by Lockheed-Martin/Aeronautics. Any expressed opinions, ndings, conclusionsor recommendations are the authors and not necessarily represen-tative of those of Lockheed-Martin/Aeronautics. We are grateful toJoris Bracke of Integrated Material Control Engineering, n.v. Genk,Belgium for measuring the stiffness values for the experimentalfoams. The authors are also grateful to Professor JohnEatonandDrs.Christopher Elkins and Andrew Onstad at Stanford University forproviding a metal foam sample and introducing us to the conceptof reproducing metal foams using additive manufacturing.

nces

. Ashbtal FoaGibsoiv. Pre. Degi2.hosh

lular M. DunaCansiz2 (20

. Murrnandndon). Murrdina, Doppeoebb

trum.. Murr, MA,Gibso.D. M. Erk,. Murrnand009)ry and conclusions

ty to fabricate stiff Ti6Al4V open cellular foams usingonstrated and described in this research program is

novation not possible by other non-additive manufac-essing technologies. In fact, the stiffnesses or elasticthese open cellular Ti6Al4V foams vary with den-ally relative stiffness versus relative density) consistentibsonAshby foam model [2]. Moreover, the stiffnesssely with porosity or pore density consistent with lit-es for a number of metal and alloy systems, especially12,13].study we have fabricated open cellular foams hav-lid and hollow cell wall or ligament structures. Theseructures have different cooling rates in contrast toid monoliths of Ti6Al4V built by EBM which pro-artensite formation or granular -phase which areixed with rened, acicular (Widmansttten) -phase

ure. This microstructure renement in the cellularand especially in the thin walls of hollow cell struc-otes higher microindentation hardness and residualdeed the hardness increase for the foam cell struc-trast to solid, fully dense monoliths, can be as high as

Refere

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[4] A. GCel

[5] D.C[6] O.

A49[7] L.E

Her(Lo

[8] L.EMeT. H

[9] G. RIns

[10] L.Eing

[11] L.J.[12] N.G[13] K.A[14] L.E

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Characterization of Ti6Al4V open cellular foams fabricated by additive manufacturing using electron beam meltingIntroductionExperimental methods and analytical issuesResults and discussionSummary and conclusionsAcknowledgementsReferences