The Optimization of the Cryogenic Processing Al-Cu Alloys

7/31/2019 The Optimization of the Cryogenic Processing Al-Cu Alloys

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A R C H I V E S

o f

F O U N D R Y E N G I N E E R I N G

Published quarterly as the organ of the Foundry Commission of the Polish Academy of Sciences

ISSN (1897-3310)Volume 7

Issue 3/2007

141 146

27/3

A R C H I V E S o f F O U N D R Y E N G I N E E R I N G V o l u m e 7 , I s s u e 3 / 2 0 0 7 , 1 4 1 - 1 4 6 141

The Optimization of the Cryogenic

Processing Al-Cu Alloys

A. Stankowiak a,*, A. W. Bydaekb*

a Polytechnic Institute, State Higher Professional School, St Mickiewicza 5, 64-100 Leszno, Polandb Mechanical Department, Zielona Gra University, St Podgrna 50, 65-246 Zielona Gra, Poland

* e-mail:[email protected], [email protected]

Received on 16.04.2007; Approved for printing on: 27.04.2007

Abstract

In the article was introduced the investigations defining optimization of the cryogenic processing after saturating the alloy AlCu4, 7. The

qualification of the influence this processes was planned (in the function of temperature and time) on microstructure and the mechanical

proprieties of this alloy. There are accept the wide range of the temperature 175 oC 350oC there made possible the settlement of the

influence of the temperature of aging on the kinetics of the break-up of the permeated with solution and then on the change of

microstructure and mechanical proprieties. There were applied the times of aging from 30 to 240 min. Results of investigations were

compared with results after such thermal processing itself without the cryogenic processing after saturating.

Keywords: Investigation of DTA, Cryogenic processing, Saturates, Ages, Dispersal hardening

1. The introduction

The alloys of aluminum are applied where higher properties in

the comparison with aluminum and are required universally there.

The cryogenic processing after saturating and then aging the alloy

AlCu4, 7 have the principal influence on enlargement of the

properties higher than the applied traditional methods of

hardening.

Well-known from the literature conduct in the thermal

processing of the chosen alloy AlCu4, leading to the optimum

effusion effect consolidations together with with coming into

being microstructure, figure 1 represents. The order of the stages

of hardening inclusions of the alloys of aluminum with the copperruns according to. [1] as follows:

they stood the supersaturated solutionGP I zoneGP IIzone

(phase ") phase '(Al3,6Cu2)

phase (Al2Cu)

where the zone GP Guiniera-Prestona zone

Fig. 1. The patern of the thermal processing (together with arising

microstructure) causing the effusion consolidation of the alloy

AlCu4 - the so-called traditional method [2]

In the result of the cryogenic processing the cramp of every

solid body follows - the dimensions of elementary mobile phone

change. Atoms approach to each other on clearly smaller

distances. They are possible solutions in the face of this:
mailto:[email protected]:[email protected]:[email protected]:[email protected]:[email protected]


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1. change of the dimension of the atom.

2. more thick packing up atoms in the crystalline net.

Second solution is true seems in the alloys of metals. If this

is the change of packing up strange atoms so hardened clearly

influences sail effusion processes particularly in alloys. In the

initial stages of the secretion the decisive part play in Vacancythese alloys. In the face of this the hypothesis, that effusion

processes in the permeated with alloys of aluminum will run

differently than without her. The similar situation sets in steels [3-

8]. We get permeated with the carbon martenzit after tempering.

He results that during the cryogenic processing there are change

of the position of the atoms of carbon in the nets of martenzit. The

atoms sets from hitherto existing investigations hatches

tetroendonics occupy, and after the processing cryogenic

octoendronics. The acceleration of effusin processes follows in

the result the change of the position of the carbon atoms. There is

the formed emission of carbides smaller and more spread [6,7].

The similar sequence appears while aging alloys Al-Cu.

Mechanism of effusion of intermetallic phaze from the

permeated with solution of-Al is the basis to the obtainment ofgood mechanical proprieties. From conducted earlier

investigations of the influence of cryogenic processing after

saturating on the processes of aging [10-13], he results that

processing this accelerates the processes of aging. The similar

influence exerts now as they hardened stood on the course of

absolving [4-7] and the similar result can call out - the

enlargement of mechanical properties. These properties are the

result setting while aging effusion processes. One can notice the

influence of the cryogenic processing after comparing with the

properties of the got meringues of the cryogenic processing.

Checking this hypothesis is the aim of our work.

2. Material and the methodology ofinvestigations

In investigations there are use synthetic alloy AlCu4, 7 about

the composition to chemical Al 94,85 %, Cu 4,69 %, Fe 0,20 %,

Si 0,08 % different approx. 0,15 %, in which the content Cu is

close the maximum of content in the permeated with solid

solution.The industrial casting alloy AlCu2,8-Si10 was also

subjected the cryogenic processing, found in this the way the

presence of silicon as the additional component.

Full analysis leading to the optimization of the cryogenic

thermal processing was conducted for the alloy Al.-Cu4, 7.

Samples were warmed to the temperature 520oC, kept in this

temperature by 10 hours, and then cooled to the temperaturequickly surroundings in water. The next part of samples was

subjected more far refrigeration to the temperature of liquid

nitrogen (-196oC) and holds out 1 the hour. The course of

saturating and aging represents on the fig. 2.

Fig. 2. The patern of the course of saturating and aging with

the cryogenic processing

The analysis of the process of the secretion of strengthening

phaze (Al2Cu) from permeated with alloy AlCu4, 7 was made onthe basis of the DTA investigations (fig.3).Warm samples to DTA together with patterns with the speed

8C/s to the temperature 520oC, the protective atmosphere was not

applied. The large speed of warming to distinguish was applied

stepping out on crooked DTA spades. Results of saturating and

aging 90 C let distinguish all four the main thermal effects. All

pikes set on oneself (particularly spades II and III). The maximum

first spades 100 appear in the temperature approx. C, maximum

second in approx. 200 C, maximum third somewhat above 300

C, and maximum fourth in 420 C. Saturating in 141 C causes

cuts the spades of first with the shift of his maximum in the side

of higher temperatures and clearly decrease spades second. Third

spades is shifted in the side of lower temperatures and his

maximum 280 step out in the temperature C. Effect fourth isvisible well and shifted in the side of higher temperatures, his

maximum is in the close temperature 450 C. Saturating in 191

C influenced minimalizing the size of effect second, however

spades first moved in the side still higher temperatures, effect

third was very clear - his maximum is shifted in the side of

somewhat higher temperatures (approx. 270 C), spades fourth is

clear, his maximum is close 460 C. Saturating in 300 it C

caused the renewed weakness of effect first and second, is smaller

in thirds place. Effect fourth, and his maximum steps out in the

close temperature 470 C. The great had influence on the singling

out stepping out thermal effects the aging in temperatures approx.

90 the C. The growth of the temperature of aging caused next

decrease spades first which stopped to be visible just after aging

in 300 C. The second effect stopped to be visible after aging in

191 C, and third even marked his presence after aging in 300

changing the temperature of one's maximum somewhat C. Pik

fourth was present on all graphs fig.3.


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Fig. 3. The summary graph of courses DTA

Table 1.

The composition of settled and analyses DTA of the optimum

parameters of the thermal processing samples AlCu4, 7

Conducted investigations thermal DTA let get informationabout the course of phase alternatively stepping out in the process

of saturating and aging alloy AlCu4, 7.. Optimum temperatures of

aging for alloy AlCu4, 7 were established on the basis of got

results-graphs DTA and the analysis of the literature which was

introduced in plan of investigations (table 1).

The hardness of the alloy was qualified in the test Brinella.

The extension relative of the alloy and the endurance on the

expansion was qualified in the static test expansion. The

dimensions of samples to the investigations of endurance on the

expansion were executed with the heads thread. The machine

stamina INSTRON model 4485 was applied , the speed of the

expansion of 3mm / the faces, the range of the head measuring

200kN, temperature 23oC, moisture 38%.

Metallographic sight was made to the investigation of the

microstructure the alloy on the transverse samples sections. The

observations of microstructure were conducted using the optical

metallographic microscope OE-4 PZO. Samples were digested theKeller reagent.

Made from the AlCu2,8Si10 alloy was used to the

investigations of the casting alloy of Si trunk of car starter (fig.

4). Investigation this has the aim the qualification of the influence

the cryogenic processing on the change of propriety stamina of

the multiple saturating technical alloy.

FN

Fig. 4. The cast the trunk of the car starter

3. The results of investigations and theiranalysis

The results of the DTA investigations represented all four

stages of appearing while aging the alloys Al-Cu of phaze.

Comparing these results with the literature, that the maxima are

shifted in the side of higher temperatures somewhat. Received

results allow to the following interpretation:

1. zone G-P - the first pikes (range of secretion to 90 C),

2. secretion of the second pikes (the range secretion to

approx. 240 C),

3. secretion of the third pikes (range of secretion to 440

C),

4. the fourth pikes the secretion equilibrium (the rangesecretion to approx. 520 C).

The change of the mechanical proprieties of the alloy AlCu4, 7was qualified in dependence from temperature and the time ofaging with the traditional and cryogenic processing on the basis ofthe measurements of hardness. It was affirmed that the hardnessof the studied alloy depended on conditions of effusionstrengthening (fig. 5).

The kind of

the thermal

processing

Temperature

[ C]Time [h] Cooling

Saturating

30 60 120 240

175

Saturating in

appointed

temperatures and

times

In water to

the

temperature

of

surroundings

{ the

investigation

of hardness

Re, Rm, Ar)

200220

275

300

350

200

220

275

300

350


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40,050,060,070,080,090,0100,0

110,0120,0

30 min 60 min 120 min 240 min

HB

200C OT 200C OK.

Fig. 5. The comparison of hardness after aging in temperature

200oC and the time of aging 30-240min with the use of the

processing of traditional (OT) and cryogenic (OK)

The hardness of samples grows up with the outflow of the time

for traditional and cryogenic processing (fig. 6) in the

compartment of the temperatures of aging from 175oC to 220oC,

samples the highest hardness are characterize after the processing

cryogenic aging in the temperature 200oC and the time ages 240

min.

The hardness of samples diminishes with outflow of time for

the range of the temperatures of aging from 275oC to 350oC. But

he is higher in the relation to the traditional processing for the

majority of samples subjected hardness to the cryogenic

processing. Cryogenic processing and the conditions of

strengthening also influence stamina proprieties (R0, 2, Rm) and

plastic (A5). The conventional border of plasticity R0,2 he

increases and endurance on the expansion of Rm of the aging

alloy together with with extension of the time of aging and the

temperature of aging- to 220oC (fig. 7). The more far growth of

the temperature of aging and the time of aging causes lowering of

border of plasticity and endurance on expansion (fig. 8).

The change of hardness, the stamina properties of the alloy

AlCu4,7 in the time reflect the kinetics of the secretion of

consolidating phaze (Al2Cu) in dependence from temperature

and the time of aging. The comparison results own investigations

from given literature he allows to thesis , that mechanism of aging

alloy AlCu4, 7 in the temperature about 100oC begins from

creating the zones of GP. The DTA graph of aging (fig. 3 )

showns thyse. The observed more far growth of stamina

proprieties, he is the hardnesses the result of the secretion of

metastable phaze indirect and , until to being establishing

stable equilibrium phaze (Al2Cu). While aging in higher

temperatures 175- 220oC does not step out the stage of arising

oneself the zones of GP, and the strengthening the alloy is the

result of the secretion metastable phaze indirect and , they

are this the strong emission which they strengthen the alloy.

Maximum stamina proprieties, hardness appear in investigations

in the temperature 200oC after 120 and 240min, are the result of

the presence in microstructure partly inclusions of phaze and

(fig. 9).

40455055606570

30 min 60 min 120 min 240 min

HB

350C OT 350C OK.

Fig. 6. The comparison of hardness after aging in temperature350oC and the time of aging 30-240min with the use of the

processing of traditional (OT) and cryogenic (OK)

120140160180200220240260

30min 60min 120min 240min

0,2%-ReMPa

220C 220C

Fig. 7. The comparison of the value the border of plasticity after

aging in the temperature 220oC with the use of the traditional

processing (OT) and cryogenic (OK)

200220240260280300320340360380

30min 60min 120min 240min

-RmMPa

220C OT 220C OK.

Fig. 8. The comparison of the endurance value on expansionafteraging in the temperature 220oC with the use of the traditional



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Fig. 9. The microstructure of the AlCu4, 7 alloy after traditional

(OT) processing aging in the temperature 200oC and the time of

aging the 240min of the area 240x

The microstructure of samples after saturating and cryogenicprocessing and aging changed together with with the temperature

of aging from 175oC to 350oC. The microstructure of samples after

the traditional processing also changed together with with the

temperature from 175oC to 350oC, until to the atrophy of the

grains of the warp, he follows the spaces of the alloy. The very

large difference steps out in microstructure between samples aging

in this alone temperature and the same time of aging. They differ

not only size of the grains of the warp, but also the emission of

CuAl2 phaze.

The use of the higher temperature of aging 275-350oC the

time shortens to appearing oneself higher usable proprieties to

30min, and these fall after the longer time of aging the value.

Decrease these is caused propriety appearing phaze equilibrium

(Al2Cu) whose particles expand while more far aging andundergo coagulation (fig. 10).

Fig. 10. The microstructure of the AlCu4, 7 alloy after cryogenic

(OK) processing aging in the temperature 350oC and the time of

aging the 240min of the area 240x

Optimum parameters registered in the investigations of the

alloy were chosen to the investigations of the cast of starter made

from the alloy of Si Al.-Cu.The influence the thermal processingon the change hardness, what set in the trunk of the starter after

aging in it was analysed in temperature 200oC and the time of

aging 12 h with the use of the traditional and cryogenic

processing drawing 11 represents.

Temperature 505C ; t 12h78,45 0,8

69,56 0,9

0102030405060708090

200C OT 200C OKTemperature

HB

Fig. 11. The hardness after aging the trunk - Al.-Cu2.8-Si10, in

the temperature 200oC and the time of aging 12h with the use of

the processing of traditional (OT) and cryogenic (OK)

The influence of the thermal processing the strength of the

expansion of THE FN which set in the trunk of the starter after

aging was analysed in temperature 200oC and the time of aging

12godzin with the use of the traditional and cryogenic processing

it was introduced on drawing 12.

Temperature 505C t12h1440,5 10

1396,6 8

136013801400142014401460

200C OT 200C OKTemperature

maxF kN

Fig.12. Strength max FN after aging the trunk in temperature

200oC and the time of aging 12h with the use of the traditional


The change of the paintings of the microstructure which set

in chosen optimum samples conducted for the trunk of the starter,

after saturating and aging in temperature 200oC and the time of

aging 12h, and then drawing 13. illustrates with the use of the

cryogenic processing.


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Fig. 13. The microstructure of the alloy, AlCu2, 8Si10 after

saturating in the temperature 200oC and time 12h (area 240x)

4. Recapitulation and conclusions

Conducted investigations the influence of cryogenic

processing after saturating on the aging processes of the AlCu4.7

alloy clearly showed, that the cryogenic processing accelerates in

the range from 175oC to 220oC the processes of aging and small

steps out her influence in compartment 220oC to 350oC . The

cryogenic processing of the industrial alloy was conducted in the

most profitable conditions

It was showed that the cryogenic processing after saturating

exerted the very essential influence on the course of effusions

processes and could played the essential part in the process of

aging. Raising usable and stamina proprieties hardened of

aluminum alloys was affirmed. Interesting for these investigations

magnificent oneself change in the profiles of propriety until aging.Described investigations were treated as the indication of the

advisability of utilization the cryogenic techniques to improving

the propriety of casts from light alloys.

References

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[2] Blicharski M.: Wstp do inynierii materiaowej. WNT2001.

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[4] D.N.Collins Deep Cryogenic Treatment of Tool Steel: aReview Heat Treatment of Metals 1996 s.40.

[5] D.N. Collins and J.Dormer Deep Cryogenic Treatment of aD2 Cold work Tool Steel Hear treatment of Metals 1997

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[6] R.Ebner, H.Leitner, D.Caliskanogulu, S.Marsoner,F.Jeglitsch Methods for characterising the precipitation of

nanometer sized secondary carbides and related effects in

tool steels Zeitsrift fur Metallkunde 92 (2001) 7 s.821.

[7] D.Mohan Lal, S.Renganarayanan, A.Kalanidi Cryogenictreatment to augment wear resistance of tool and die steels,

Cryogenics 41 (2001) s.149.[8] R.Mahmudi, H.M.Ghasemi and H.R. Faradij Effects of

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[9] D.A.Porter, K.E. Easterling Phase Transformations inMetals and Alloys. Van Nostrand Reinhold Company, New

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[10]H. Kacar, E. Atik, C. Meric The effect of precipitation-hardening conditions on wear behaviours at 2024 aluminium

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142 (2003) 762-766.

[11]I.Wierszyowski, S.Wieczorek, A. Stankowiak, J.Samolczyk Kinetics during supersaturation and ageing of the Al.-4.7

mass % Cu alloy : grain size , dilatometric and DTA studiesJournal of Phase Equilibria and Diffusion vol.26. No.2005

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[12]I. Wierszyowski, A. Stankowiak, S. Wieczorek Cryogenictreatment of suprtsaturated Al-4.7%Cu alloy. The influence

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Conference 12-14 October 2005 Kliczkw Poland.

[13]A. Stankowiak, A.W. Bydaek Wpyw obrbkikriogenicznej po przesycaniu na wasnoci mechanicznestarzonego stopu Al4,7Cu X Krajowa Konferencja

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The Optimization of the Cryogenic Processing Al-Cu Alloys