The influence of squeeze casting parameters on the mechanical

The influence of squeeze casting parameters on the mechanical

OUN
Pvbrishsd quartw as the organ dthe Foundry Com-n
of the Palish Academy of Sciences
The influence of squeeze casting parameters
on the mechanical properties
of AIZnSMg alloy
A. Zyska "'*, 2. Konopka ', M. t q g i c ~ v k a qM. Nadolski"
%cpafl!ncnt of Foundry, Tcchnical Univcrsily of Czqstochowa, uI. Armii Krajowcj 19,42-200 Czqstochown, Polska
* Corresponding author's c-mail: zyska @mim.pcz.czcn.pl
Rcccivcd 26.02.2008; accepted in revised form 12.03.208
Abstract
Mcchnnicnl propcrtics of castings prodl~ccdby thc dircct squcczc caning mczhod havc hccn cxainincd and thc rcsulis hnvc hccn prcscntcd
in ihc work. Thc K,, and A5 distribulions have bccn analysed Tor cxtcrnal and intcrnal parts of thc slah tcst caning ror various dic
tcmpcrarilrc and prcssurc OF squcczing valucs. Sqi~cczinghas bccn performed at rhc dic rcrnpcmlurc cqi~nllo 150°C or 250°C changing ihc
RcsuIrs of rnctnllngrapliic cxamiiia~ioiilisvc hccn prcscn~ctland
prcssurc o l squcczing from thc atmospheric onc to thc valuc or 90 Mk.
1he stntc~uralchnngcs in castings solidifying under prcssurc have bccn nsscsscd in comparison 10 dic cast itlgs. Oplimum paramcrcrs or
producing thc high-srrcnglh canings ma& of'AIZn5Mg nlloy havc hecn dctcr~nincd.
Kcywarcls: At alloys. squcczc casting technology. mcchanical propcflics, s~mcturc.
1. Introduction
Squcczc casting also cailcd liquid mclal forging is applicabEc
for production of high quality casting. mainly or att~rninium
alloys. This mcthod aIIows for achieving castings with Finc grain
structurc and withoui ~nicmal:dcfccts chnractcristic For gsavily dic
casling and prcssurc dic casting tcchnologics. Mcchanicnl
propcflics of alloys squcczcd in ~ h cEiyuid statc oftcn cxcccd thc
valucs rcnchcd by ~ h cpIaslic worked matcrbal. Sqr~cczccastings
cxhihit also grcat dimcnsionnl accuracy and g o d surracc
srnoorhncss I 3 -91.
Thc high dcgrcc or structurc rcfincrncnt rcs~iltsfmm an
intcnsivc hcat cxchangc in thc plungcr dic - casting - dic block
system. Thc continuous prcssurc cxcrtcd on rhc sol~difyingalloy
incrcascs thc hcat rnnsrcr cocClicicnt and clirnina~cstbc cooling
gap. thus d u c i n g rhcrmal rcsinancc. what results in an incrcascd
supercooling and gcncrazion of a Sargc n u m k r nC crystallisat ion
nucici I. 11). I11. Thc dcgrcc of supercooling o l ~ h cliquid mctal
i s corrclatnl with thc icmpcsarurc o f squcczing. Applying of
prcssurc at thc tnnpcratzirc closc to llic solidirying point is rhc
most crfcctivc [ 10, 121. Thcn thc inaximurn supcrcoolinc OF rhc
alloy and thc grcatcst incrcnsc of ~iirclcnlionraic occt~r,whcreas
ton large ovcrllcating or t hc alloy can allnost coinplctcly nulliry
t hc hcncficial crfcct of ihc applicd prcssurc, lligll prcssurc also
clirninafcs arising oF gas buhhlcs in ihc casting and rcinnvcs
shrinkagc macm- and microporosity. rhus disiinc~lyilrrcasiiig thc
dcnsiry o f stampings [ 10. 131.
Squcczc castings arc partb~tsrly dcsircd Tor hydraulic
constructions. IIydraulic clcincnts working l~ndcrhigh prcssurc
valucs havc to cxhibit high prcssurclightncss. Squcczc castings
significantly surpass commonEy used graviiy die casiings in this
rcspccl [ 141.
Thc prcscnt work has hccn airncd to dctcr~nincthc infli~encc
of two basic paramctcrs or squcc7c casting. i.c. the pressure of
sqircczinp and thc dic tcmpcraturc, on rncchanical propcnics of
AIZnSMg nlloy.
A R C H I V E S of F O U N D R Y E N G l N E E R l N G V o l u m e 8 . S p e c i a l I s s u e llZ008, 347-351)
367
2. The material and methodies of its
examination
The cxarnination has hccn performed Tor thc standard
ENAB-71000 (CNAR-AtZnSMg) alloy o f thc following
chemical cornpsilion: 92.50%AI. 0.3%Cu, 0,32%Mn, 0.57%Mg,
0.48%Cr. 0.30%Ni, 5.25%2n.
0.I8%Ti, total contcnt OF
impuritics (Ph,Sn) 0.10%. Thc rnclting proccss havc procccdcd
in thc induction cruciblc Furnace PIT 50SI4QQ. Slab-shapcd
spccimcn castings o f dimcnsions 200x 1 00x20 rnm havc been
p d u c c d in khc die block rnounrcd on thc PI lM-250C hydraulic
prcss. Pressing in a liquid state has bccn rcalised at constant alloy
rcmpcmlurc cquaI to about 650°C and variahle pressurc and dic
tcmpcrazurc valucs. Thc cxamination has hccn plannod for the
prcssurc range From the atmospheric onc to thc valuc o f 90 MPa
hy incrcmems o f 30 MPa, and for two valucs of dic tcrnperaturc.
• external specimens
Iinternal specimens
26~
-
namely 3 50°C and 250°C. McchanicaE properties have bccn
cxamined according to thc PN-9 1111-04310 standard. using tensilc
specimens with gauge Icngth-to-diamctcr ralio o f 5: 1, which have
bccn rcstcd by mcnns o f zhc ZWICK- 1488 scrvo-hydraulic testing
machine. Thcsc propcflics havc hccn dctcrmincd both for thc
"internal'" spccimcns (cut out o f thc ccntral part of cach casting)
and for !hc *'cx!crnal" oncs (takcn from thc corncrs of cach
casting). Microslmctum~ohscrvations have bccn pcrformcd by
mcnns of thc Nikon Epiphor optical microscope Tor samplcs takcn
both from corncrs o f castings and Tmm thcir ccnznl pads.
I00
atm.
30
60
90
Pressure of squeezing, MPa
Pig. 2. Tensile strcngth OF rhc AIZnSMg nlloy dctcrmincd for
"cxtcmal" and "intcmal" spccirncns vcrsus rhc pressuse or
squcczing; dic tcmpcraturc cqual ta 250°C
W external specimens
internal specimens
16
3, Examination results
Thc significant shrinkage and thcrmal strcss arisc during thc
squccr.c casting proccss. The continuous prcssitrc cxcrtcd on thc
sotidifid cxtcrnai parts of the slah hindcrs frcc shrinkage o f its
matcrinl and gcncratcs tcnsilc strcss in thc ccntrnl part o f
a casting.
H external specimens
W internal specimens
0
atm.
30
60
90
Pressure of squeezing, HPa
Fig. 3. Elongation As or the AtZn5Mg alloy dercrmincd Tor
"cxtcmal" and "imcrnal" spccimcns vcrsus thc prcssurc of
squccting; dic tcmpcrazurc cqual 10 150°C
Suvrimpowd on thc strcss field resulting from ~ h ccxrcrnal
pressurc i s additional strcss ficld arising duc ro thc large
-atm.
30
60
90
Pressure of squeezing, MPa
Fig. 1. Tcnsilc strcngth or thc AIZnSMg alloy determined
for "external" and "inlcrnal" s p c i mens versus the
pressure of squeezing; dic tcmpcraturc cqual 10 150°C
dlffcrcnccs in ~ h lcmpcrarurc
c
gradient over thc slah cross-section.
Thc conscqucnce of thcse phenomena is thc non-uniform
dislribu~iono f mechanical propcnics.
The prcscntcd rcsults (Figs 1-4) indicatc that the uniformity of
thc cxamined provflies in the slab-likc: casrings pmduccd of thc
AIZnSMg
d c ~ n d sboth On lhc tcm~ralurcand On lhc
casting tcchniquc. Gravity castings produccd al thc tempcratare of
150°C have cxhibitcd thc tcnsilc strcngth difFcrcnce bctween the
A R C H l V E S of F O U N D R Y E N G I N E E R I N G V o l u m e 8 . Spectar I s s u e 1 1 2 0 0 8 . 3 4 7 - 3 5 0
crtcrnal and thc internal slab pan exceeding 80 MPs (Fig. I).
Aficr increasing the dic tcm,raturc
(his diflcrcnrr h u bccn
seduccd. hut still rcachcd thc Icvcl of about 40MPa (Fig. 3).
P l ~ i c i l y(W in g r a d ~
castings changes vmnling lo similar
relationships ((Figs 2 and 4). Sqt~cczccaslings produccd at the dic
I~rnperaIttrcof I5D.C also show significanl diffcrcnc~srcgrrding
strcngth and plasticity of thc sclcctcd slab pwts (Figs Iand 23, but
thcy acquirc ~ h noticeably
c
lowcr lcvcl than lor gravity castings.
Rising lhc icrn~raturcto 250°C dong with thc influcncc of
cx~crnalprcssurc 30-90 MPa results in lhc unihm distribution of
rncchanical provnics, over the siah casting (Fig. 4) This provcs
that thc dic tcmpcnturc i s dccisivc ior thc distribdon o f
mcchnnical pmpcrtics of squcczc castines.
IIexternal specimens
16
.
.
.
internal specimens
Fig. 5. The AIZnSMg nlloy strtlculrc, gmvily rlic css~ing.dic
tcmp. 250°C. slah comcr, mogn. IOOx, ctchcd with 4% IIF
14
0 .
atm.
30
60
Pressure of squeezing, MPa
90
Fig. 4. Elongatinn As of thc AIZnSMg alloy dacrmincd for
"cxtcmal" and "intcrnol'* s p i m c n s vcrsus thc prcssurc o l
squcczinp: dic tcrnpcmtilrc cqual to 250°C
Fig. 6. Thc AIZnSMg alloy siructirrc. gravity dic casting, dic
fcrnp. 2 5 0 T . slah ccnzrc. Inagn. tOnx. ctchcrl with 4% Fir
'She mcasurcmcnt rcsults concerning rncchanical propcrtics or
castings prcscntcd in Pigs 2 and 4 show distinctly that the squmrc
casting rncthod prcvails ovcr thc gravity dic casting. Squccrc
castlngs cxhihit twicc as Inrgc elongation as thc castinps p d u c c d
by ,he gravity dic carting rnclbod. Mormver. thc rquecrc
t~chna~o~ypmvidcsfo~~h~~ni~~rmdistr~hution~fstrenglhand
plastic propertic%.which umin the optimum vsluer M the presaurc
of squccf~ngor 30 MPa and rhc dic rcmpcmturc of250°C.
'I.hc rhnractcriaic lcslurc o l the carting solidifying under t l ~ c
cx~crnnlprcssurc i s grain refining and rcsulring strenghtcning of
thc nlloy. The shrinkage gap arires much lecr ilndcr tllc prcssurc
ennditions of qnlidirying rhan it doer lor gravity dic casting
solidifying. l lent cxchrngc pmcecds 1 n prenlcr rrtc in ihc
prcssurc dic+casiing sygcm andthc sirpcrcuoling or lhc alloy
incrcascs. Thc result of crystallisation pmccss intcnsificalion is
the refining o i n stn~crurc. Figs 5 and 6 show lhc slruclun: of
gravity dic caqling in thc sl;th corncr and in i ~ sccnlnl part.
resprivcly. This casting cxhih~rsthc singlc phasc grain struclun?.
1:ig. 7. Thc AlXnSMvig nlloy structure. rquce/c crsling, prcsrurc OF
but rhc casring parts diflcr with rcspcct trr tbc grain sizc. Numbcr
squeezing 30 MPa. dic Icmp. 250"C, slah cnrncr.
of grains per LI~II a m IS significantly grcatcr In rhc slab comcr
magn. 10Dx. crchcd with 4 8 ISt:
than in its ccntrc.
A R C H I V E S o f F O U N D R Y ENGINEERING V o l u m e 8 , S p e c i a l I s s u e Tl2OOB. 3 4 7 - 3 5 0
4, An intcnsivc hcat cxchnngc in thc prcssurc dL - squcczc
casting systcm rcsults in an incrcasc o f thc nlloy supcrcooling
and dccrcnscd changcs in tcinpcraturc gradient across thc
slab-likc casting. An unirorm sttuctl~rco f high rcfincmcnt
dcgrcc is achicvcd, as wclt as thc l ~ n i f o r ~distrihtrtion
n
ol
rncchanical propcrtics.
Refcrcnces
[ l ] J. Batyscv, Crystallisation of mctnls and ollnys undcr
prcssurc* Metallurgy, Moscow ( 1 977) (in Russian).
[21 M. Pcrzyk. S. \Vastkicwicz. M. Kaczorowski, A.
Jopkicwicz. Casting. WNT, \Varsnw (2000)(in Polish).
[31 S.W. Kim, D.Y. Kim. W.G. Kim. K.D.Won, Thc study on
Piy. 8.Thc AIZnSlvIg alloy srmaurc. squcczc casting, prcssurc of
stlucci..i~ry3 0 MI'.!. dic Icrnp. 2SI)"C. slah ccnrrc, m a g . E OOx,
ctchcd wirh 4% 1 I F
A clinngc ill tlic priliinry u-plinsr crystals morphology occurs
tluc lo tlie cxtcrn;il hrcc applying. Sqr~cczc castings cxhihit
a vcllii!;ir-rlct~dri~icsin~cturc(Figs 7 and 8). As far as thc dcgrcc
or str~tcturcrcfrrlctncnt i s IQ hc asscsscd. one can state thzt the
s i x or cr-plinsc crystnls is similar for rhc cntirc slab casting.
Sqiicc;.ing results in an incrcasc of thc alloy supcrcooling, hut I ~ C
tcmpcra~urcgmdicn~across thc slab vary to thc lcss dcgrcc than
Ibr ~ h cgravity tlic caslings. Thc unirorm strwcti~rco f sqllccac
castings is rcsponsihlc For thc uniform distrihi~tionof mcchanical
propcrtics. Morcovcr, thcsc castings arc prcssurctight and rhc
inrcrnal dcfccts charactcrislic for gravity dic casting technology,
i.c. shrinkage porosity and gas porosity. arc compIcicly climinalcd
at thc prcssurc uf sqitcc~ingct~unllo 3 0 MPn.
4. Analysis of results and final
conclusions
3 . Thc rcchnoloyy of sqrrcc/c casting cnsurcs producing of high
quality cnsrinys o r AlZn5Mg alloy cxhihiting arcngih of chc
lcvcl a h u t 230 MI% at ~ h unit
c elongation cxcccding 15%.
2. Thc influcncc or rhc prcssurc dic tcmpcraturc is dccisivc for
climina!ing Ihc diffcrcnccs in mcchnnical propcrtics bctwccn
varintts pans or a S~IICC~C cns~il~y.
Optimum and uniform
d~strihul~on
of p m v n i c g i g achicvcd for thc prcssure OF
squcci..ing ctlitnl ln 3 0 Ml'a and thc dic rcmpmturc of 25°C.
3. 'I'hc influcncc of prcsst~rcon thc AlZnSMg altoy solidifying i s
rcvciiltrl hy tlic morphology of tlic primary a-phase crystals.
A chnngc frn~iigrain to tbc cellular-dcndrit ic srruclurc i s
ohscrvctl.
A R C H I V E S of
FOUNDRY
charac~cris~ics
of hcat trcatmnt of the dircct squcczc cast
7075 wrought AI alloy, Matcrials Scicncc and Engincering.
12304-306 12001 ) 72 1-726.
[4] L.J. Ynng, Thc cffcct of casling tcmpcnturc on thc
propcnics of sqiicczc cast alurninitiin and zinc alloys. Journal
of Ma~crinlsI'rnccssing Tcchnology. vol. 140 (2003) 3'11-
396.
[S] T. M. Yue, Sqt~ccaccnaing of high-strcnczh aluminium
wrought nlloy AAT0 10. Journal of Matcrinls Processing
Tcchnology, vol. 66 ( 1 997) 179- IR5.
[6] S. M. Skolinnos, G. Kioiinsidis, T. Xatzilotio~i, Efrcct of
appl icd prcssurc on t hc microslructurc and mcchanicnl
propcrtics o f squcczc-cast aluminum Act606 E alloy.
Marcriais Scicncc and Enginwring. vol. A23 1 ( 1 997) E 7-24.
(71 M.T. Abou El-khnir, Micmslnicturc charactcrizarion and
tcnsilc propcrlics of squcczc-cast AISiMg alloys, Marcrials
httcrs. vol. 59 (2005).X94- 900.
IS] S.W. Youn. C.G. Kang, P.K. Sco, Thcrmal
fluidsolidification analysis of automohilc part by horizontal
squcczc casting proccss and cxpcriincntnl cvatuarion, Jouninl
of Matcrials Pmcssing Tcchnology 14h (2W)294-302.
(91 M. Ilajdasz. J. Chmicl, CIassificn~ionof rncthods o f mctnl
pressing in tbc dic. Scicnlific E'apcrs o f Marinc Acadcrny in
Szczccin. vol. 41 (1443) 35 (in Polish).
[I01 B. Cliaicrjc, A.A. Das. Thc llritish Foundry~nan,vol. 14
(1973) 1 IS.
[ I11 R.F. Lynch, S q t w c x Casting, Malcrial Dclawarc Vatlcy
Charincr, ASM. Dochlcr-JnrvisNL Industries. Tolcdo (1973).
[ 121 M. Hajdasz, Barocrystallizntion nT mctal alloys. Archivcs o f
Macbinc Constn~c~ion
'~cchnologics, vol. 12 11993) 45 (in
Polish).
[I31 M. Ilajdasz. Squcczc casting. Foundry Rcvicw. vol. 43,
No. 4 (1993) E 10 (in Polish).
[ 141 MctaIs Ilandbook: Cnsling, vol. 15, ASM Intcmational.
(1992).
E N G I N E E R I N G Volurno 8 . S p e c i a l I s s u e 112008. 3 4 7 - 3 5 0