**3. Results and discussion**

DSC curves obtained by heating (Fig. 1a) and cooling (Fig. 1b) as-cast specimens of the examined AlSi5Cu1Mg alloy are shown in Fig. 1. DSC curves demonstrate precisely each reactions during heating and solidification process of as-cast AlSi5Cu1Mg alloy. One can see from the figures that during cooling the reactions occurred at lower temperatures (Fig. 1b) compared to the values recorded during heating of the same alloy (Fig. 1a). Solidification process of this alloy is quite complex (Fig. 1) and starts from formation of aluminum reach (α-Al) dendrites. Additional alloying elements such as: Mg, Cu, as well as impurities: Mn, Fe, leads to more complex solidification reaction. Therefore, as-cast microstructure of AlSi5Cu1Mg alloy presents a mixture of intermetallic phases (Fig. 2). The solidification reactions (the exact value of temperature) obtained during DSC investigation were compared with the literature data (Bäckerud at al., 1992; Li, et al., 2004) and presented in Table 2. Results obtained in this work very well corresponding to the (Bäckerud at al., 1992; Li, et al., 2004; Dobrzański at al., 2007).

Fig. 2 shows as-cast microstructure of AlSi5Cu1Mg alloy. The analyzed microstructure contains of primary aluminium dendrites and substantial amount of different intermetallic phases constituents varied in shape, (i.e.: needle, plate-like, block or "Chinese script"), size and distribution. They are located at the grain boundaries of α-Al and form dendritic network structure (Fig. 2).

Intermetallic Phases Examination in Cast AlSi5Cu1Mg and

<sup>L</sup>→(Al)+Si+AlMnFeSi 558 Precipitation of

(a) (b)

(c) (d)

Fig. 2. Morphology of AlSi5Cu1Mg alloy in the as-cast state: (a,c) unetched and (b,d) etched In order to identify the intermetallic phases in the examined alloy, series of elemental maps were performed for the elements line Al-K, Mg-K, Fe-K, Si-K, Cu-K and Mn-K (Fig. 3 and 4). The maximum pixel spectrum clearly shows the presence of Al, Mg, Fe, Si, Cu and Mn in the

L→(Al)+Al15Mn3Si2+(Al5FeSi) 590

(Bäckerud at al., 1992; Li, Samuel et al., 2004)

L→(Al)+Al2Cu+Si+ Al5Mg8Cu2Si6

AlCu4Ni2Mg2 Aluminium Alloys in As-Cast and T6 Condition 23

**Bäckerud et al. Temp., ºC Li, Samuel et al. Temp., ºC This work**  L→ (Al) dendrite network 609 (Al) dendrite network 610 610

L→(Al)+Si+Al5FeSi 575 Precipitation of eutectic Si 562 564

L→(Al)+Al2Cu+Al5FeSi 525 Precipitation of Al2Cu 510 510

<sup>507</sup>Precipitation of

Table 2. Reactions occurring during the solidification of the AlSi5Cu1Mg alloy according to

Al5Mg8Cu2Si6

α-Al(FeMn)Si

β-Al FeSi <sup>5</sup>

Al6Mg3FeSi6+Mg2Si 554 532

490 499

Q-Al Cu Mg Si 5 2 86

Si

Fig. 1. DSC thermograms of as-cast specimens of AlSi5Cu1Mg alloy, obtained during a) heating and b) cooling at rate of 5°C/min

200 250 300 350 400 450 500 550 600 650

Temperature, °C

(a)

200 250 300 350 400 450 500 550 600 650

Temperature°C

(b)

Fig. 1. DSC thermograms of as-cast specimens of AlSi5Cu1Mg alloy, obtained during

**2**

**1**

**5**

**4**

**<sup>4</sup> <sup>3</sup>**

**2**

**1**

**3**






Heat flow,

μ

V

0

2

Exo

q = 5°C/min

a) heating and b) cooling at rate of 5°C/min

4



Heat flow,

μ

V


Endo

q = 5°C/min



Table 2. Reactions occurring during the solidification of the AlSi5Cu1Mg alloy according to (Bäckerud at al., 1992; Li, Samuel et al., 2004)

Fig. 2. Morphology of AlSi5Cu1Mg alloy in the as-cast state: (a,c) unetched and (b,d) etched In order to identify the intermetallic phases in the examined alloy, series of elemental maps were performed for the elements line Al-K, Mg-K, Fe-K, Si-K, Cu-K and Mn-K (Fig. 3 and 4). The maximum pixel spectrum clearly shows the presence of Al, Mg, Fe, Si, Cu and Mn in the

Intermetallic Phases Examination in Cast AlSi5Cu1Mg and

**Mn**

AlCu4Ni2Mg2 Aluminium Alloys in As-Cast and T6 Condition 25

**Mg**

**Si Fe** 

**Al Cu**

 Fig. 4. SEM image of the AlSi5Cu1Mg alloy and corresponding elemental maps of: Al, Mn,

Mg, Fe, Si and Cu

scanned microstructure. In order to identify the presence of the elements in the observed phases, characteristic regions of the mapped phase with high Mg, Fe, Si, Cu and Mn concentration were marked and their spectra evaluated (Fig. 5).

Fig. 3. SEM image of the AlSi5Cu1Mg alloy and corresponding elemental maps of: Al, Mg, Fe, Si and Cu

Fig. 5 shows the SEM micrographs with corresponding EDS-spectra of intermetallics observed in the as-cast AlSi5Cu1Mg alloy. The EDS analysis indicate that the oval particles are Al2Cu (Fig. 5a). Besides Al2Cu phase, another Cu containing phase Al5Mg8Cu2Si6 was observed (Fig. 4,5). In addition the Cu-containing intermetallics nucleating as dark grey rod, primary eutectic Si particles with "Chinese script" morphology were also observed. Fe has a very low solid solubility in Al alloy (maximum 0.05% at equilibrium) (Mondolfo, 1976), and most of Fe in aluminium alloys form a wide variety of Fe-containing intermetallics depending on the alloy composition and its solidification conditions (Ji et al., 2008). In the investigated as-cast AlSi5Cu1Mg alloy Fe-containing intermetallics such as light grey needle like β-Al5FeSi (Fig. 5a) and blockly phase consisting of Al, Si, Mn and Fe (Fig. 5a) were observed. On the basic of literature date (Liu Y.L. et al., 1999; Mrówka-Nowotnik et al., a,b, 2007; Wierzbińska et al., 2008) and EDS results (Fig. 5 and Tab. 3) this particles were identified as α-Al(FeMn)Si phase.

Fig. 5 shows SEM micrographs with corresponding EDS-spectra of intermetallics observed in as-cast AlSi5Cu1Mg alloy. The EDS spectra indicate that the oval particles are Al2Cu (Fig. 5a). Besides Al2Cu phase, another Cu containing phase AlCuMgSi is observed (Fig 5b). The results of EDS analysis are summarized in Tab. 3 versus the results obtained by earlier investigators.

scanned microstructure. In order to identify the presence of the elements in the observed phases, characteristic regions of the mapped phase with high Mg, Fe, Si, Cu and Mn

**Al Mg** 

**Si Cu** 

concentration were marked and their spectra evaluated (Fig. 5).

**Fe**

Fe, Si and Cu

investigators.

identified as α-Al(FeMn)Si phase.

Fig. 3. SEM image of the AlSi5Cu1Mg alloy and corresponding elemental maps of: Al, Mg,

Fig. 5 shows the SEM micrographs with corresponding EDS-spectra of intermetallics observed in the as-cast AlSi5Cu1Mg alloy. The EDS analysis indicate that the oval particles are Al2Cu (Fig. 5a). Besides Al2Cu phase, another Cu containing phase Al5Mg8Cu2Si6 was observed (Fig. 4,5). In addition the Cu-containing intermetallics nucleating as dark grey rod, primary eutectic Si particles with "Chinese script" morphology were also observed. Fe has a very low solid solubility in Al alloy (maximum 0.05% at equilibrium) (Mondolfo, 1976), and most of Fe in aluminium alloys form a wide variety of Fe-containing intermetallics depending on the alloy composition and its solidification conditions (Ji et al., 2008). In the investigated as-cast AlSi5Cu1Mg alloy Fe-containing intermetallics such as light grey needle like β-Al5FeSi (Fig. 5a) and blockly phase consisting of Al, Si, Mn and Fe (Fig. 5a) were observed. On the basic of literature date (Liu Y.L. et al., 1999; Mrówka-Nowotnik et al., a,b, 2007; Wierzbińska et al., 2008) and EDS results (Fig. 5 and Tab. 3) this particles were

Fig. 5 shows SEM micrographs with corresponding EDS-spectra of intermetallics observed in as-cast AlSi5Cu1Mg alloy. The EDS spectra indicate that the oval particles are Al2Cu (Fig. 5a). Besides Al2Cu phase, another Cu containing phase AlCuMgSi is observed (Fig 5b). The results of EDS analysis are summarized in Tab. 3 versus the results obtained by earlier

Fig. 4. SEM image of the AlSi5Cu1Mg alloy and corresponding elemental maps of: Al, Mn, Mg, Fe, Si and Cu

Intermetallic Phases Examination in Cast AlSi5Cu1Mg and

Intensity, cps

Intensity, cps

In et nsity, cps

In et nsity, cps

> Intensity, cps

AlCu4Ni2Mg2 Aluminium Alloys in As-Cast and T6 Condition 27

Energy, keV

Energy, keV

Energy, keV

Energy, keV

Energy, keV

Fig. 5. b) The corresponding EDS-spectra acquired in positions indicated by the number 1-5

2

3

4

1

5

The following phases were identified in the as-cast AlSi5Cu1Mg alloy based on DSC results and microstructure - LM and SEM observations (Tab. 2 and 3, Fig. 1-5): Si, β-Al5FeSi, Al5Cu2Mg8Si6, Al2Cu, α-Al(FeMn)Si. These results can suggest, that in this alloys occur five solidification reactions (Tab. 4). The data presented in Tab. 4 shows that the solidification sequence of AlSi5Cu1Mg alloy differ only slightly from this obtained by Backerud and Li (Tab. 2).


Table 3. The chemical composition of the intermetallic phases in AlSi5Cu1Mg alloy in the as-cast state

Fig. 5. a) SEM micrographs of the AlSi5Cu1Mg alloy in the as-cast state

The following phases were identified in the as-cast AlSi5Cu1Mg alloy based on DSC results and microstructure - LM and SEM observations (Tab. 2 and 3, Fig. 1-5): Si, β-Al5FeSi, Al5Cu2Mg8Si6, Al2Cu, α-Al(FeMn)Si. These results can suggest, that in this alloys occur five solidification reactions (Tab. 4). The data presented in Tab. 4 shows that the solidification sequence of AlSi5Cu1Mg alloy differ only slightly from this obtained by Backerud and Li

> **Chemical composition of determined intermetallic phases, (% wt)**

**Si Cu Mg Fe Mn** 

33 29.22 28.49

25-30 25 27.75 23-26

10-15 5.1-28 10-13 11-13

49.51 Belov, 2005

15-20 14-24 19-23 14-20 **References** 

Lodgaard, (2000) This work

Mondolfo, 1976 Warmuzek, 2005 Liu, 1999 This work

Mondolfo, 1976 Warmuzek, 2006 Liu, 1999 This work

This work

Ji, 2008

(Tab. 2).

**No. of analyzed particles** 

**Suggested type of phases** 

Al12(FeMn)3Si

10 Al2Cu 52.5

19.2 15.2 17.97

12-15 12.2 14.59 13-16

10-12 5.5-6.5 5-7 8-12

31.1 26.9 27.48

25 Si 85-95 This work

Table 3. The chemical composition of the intermetallic phases in AlSi5Cu1Mg alloy in the

Fig. 5. a) SEM micrographs of the AlSi5Cu1Mg alloy in the as-cast state

20 Al5Cu2Mg8Si6

<sup>25</sup>β-Al5FeSi

12 α-

as-cast state

Fig. 5. b) The corresponding EDS-spectra acquired in positions indicated by the number 1-5

Intermetallic Phases Examination in Cast AlSi5Cu1Mg and

a) b)

c)

Al2Cu (<lμm).

AlCu4Ni2Mg2 Aluminium Alloys in As-Cast and T6 Condition 29

Microstructure of AlSi5Cu1Mg alloy in T6 condition is presented in Fig. 6. Analyzing the micrographs of the alloy after heat treatment at 520°C for 5h it had been found that during solution heat treatment the morphology of primary eutectic Si changes from relatively large needle like structure to the more refined "Chinese script" and spherical in shape particles. Most of the needle like particles of β-Al5FeSi phase transform into spherical-like α-Al(FeMn)Si (Kuijpers at al, 2002; Liu at al., 1999; Christian, 1995) as shown in Figure 6 and 7. It has been found that Al2Cu and Al5Cu2Mg8Si6 phases dissolve in the α-Al matrix during solution heat treatment. The subsequent aging heat treatment at 250°C for 5 leads to formation form the supersaturated solid solution fine intermetallic strengthening particles of

Fig. 7 shows scanning electron micrographs and EDS analysis of particles in the investigated AlSi5Cu1Mg alloy in T6 condition. The EDS analysis performed on the phases presented in microstructure of the alloy revealed, that spherical in shape inclusions are the eutectic

220

040 220

Fig. 8. TEM micrograph of AlSi5Cu1Mg alloy in T6 conditions showing the precipitate of the



β-Mg2Si phase (a,b), and corresponding electron diffraction pattern (c)

040

440

400

024

204


Table 4. Solidification reactions during nonequilibrium conditions in the investigated AlSi5Cu1Mg alloy, heating rate was 5°C/min

Fig. 6. The microstructure of AlSi5Cu1Mg alloy in the T6 condition (a,b)

Fig. 7. a) SEM micrographs of the AlSi5Cu1Mg alloy in the T6 condition; b) The corresponding EDS-spectra acquired in the positions indicated by the number 1 and 2

**Reactions Temperature, °C** 

L→ (Al) dendrite network 610 L→(Al)+Si+Al5FeSi 564 L→(Al)+Si+AlMnFeSi 532 L→(Al)+ Al2Cu+ Al5FeSi 510 L→(Al)+ Al2Cu+Si+Al5Cu2Mg8Si6 499 Table 4. Solidification reactions during nonequilibrium conditions in the investigated

 (a) (b) Fig. 6. The microstructure of AlSi5Cu1Mg alloy in the T6 condition (a,b)

Intensity, cps

> Intensity, cps

Energy, keV

Energy, keV

Fig. 7. a) SEM micrographs of the AlSi5Cu1Mg alloy in the T6 condition; b) The corresponding

(a) (b)

EDS-spectra acquired in the positions indicated by the number 1 and 2

2

AlSi5Cu1Mg alloy, heating rate was 5°C/min

1

Microstructure of AlSi5Cu1Mg alloy in T6 condition is presented in Fig. 6. Analyzing the micrographs of the alloy after heat treatment at 520°C for 5h it had been found that during solution heat treatment the morphology of primary eutectic Si changes from relatively large needle like structure to the more refined "Chinese script" and spherical in shape particles. Most of the needle like particles of β-Al5FeSi phase transform into spherical-like α-Al(FeMn)Si (Kuijpers at al, 2002; Liu at al., 1999; Christian, 1995) as shown in Figure 6 and 7. It has been found that Al2Cu and Al5Cu2Mg8Si6 phases dissolve in the α-Al matrix during solution heat treatment. The subsequent aging heat treatment at 250°C for 5 leads to formation form the supersaturated solid solution fine intermetallic strengthening particles of Al2Cu (<lμm).

Fig. 7 shows scanning electron micrographs and EDS analysis of particles in the investigated AlSi5Cu1Mg alloy in T6 condition. The EDS analysis performed on the phases presented in microstructure of the alloy revealed, that spherical in shape inclusions are the eutectic

Fig. 8. TEM micrograph of AlSi5Cu1Mg alloy in T6 conditions showing the precipitate of the β-Mg2Si phase (a,b), and corresponding electron diffraction pattern (c)

220



Intermetallic Phases Examination in Cast AlSi5Cu1Mg and

(a) (b)

(c) (d)

Energy, keV

Energy, keV

(e) (f)

EDS spectra (e,f)

Intensity, cps

Intensity, cps

Intensity, cps

1

2

Intensity, cps Energy, keV

Energy, keV

3

4

Fig. 11. SEM micrographs (a-d) of the particles extracted from the AlSi5Cu1Mg alloy and

AlCu4Ni2Mg2 Aluminium Alloys in As-Cast and T6 Condition 31

silicon ones, whereas the rod-like and "Chinese script" shaped, are inclusions of the phase consisting of Al, Si, Mn and Fe (Fig. 2,7 and Tab. 3).

Since it is rather difficult to produce detailed identification of intermetallic using only one method (e.g. microscopic examination) therefore XRD and TEM techniques was utilized to provide confidence in the results of phase classification based on metallographic study. The microstructure of the examined alloy AlSi5Cu1Mg in T6 state consists of the primary precipitates of intermetallic phases combined with the highly dispersed particles of hardening phases. The TEM micrographs and the selected area electron diffraction patterns analysis proved that the dispersed precipitates shown in Figure 8 and 9 were the precipitates of hardening phase β-Mg2Si (Fig. 8) and θ′-Al2Cu (Fig. 9).

Fig. 9. Precipitation of strengthening β-Mg2Si i θ'-Al2Cu phases in AlSi5Cu1Mg (a,b) – TEM

Fig. 10. X-diffraction pattern of AlSi5Cu1Mg alloy

silicon ones, whereas the rod-like and "Chinese script" shaped, are inclusions of the phase

Since it is rather difficult to produce detailed identification of intermetallic using only one method (e.g. microscopic examination) therefore XRD and TEM techniques was utilized to provide confidence in the results of phase classification based on metallographic study. The microstructure of the examined alloy AlSi5Cu1Mg in T6 state consists of the primary precipitates of intermetallic phases combined with the highly dispersed particles of hardening phases. The TEM micrographs and the selected area electron diffraction patterns analysis proved that the dispersed precipitates shown in Figure 8 and 9 were the

Fig. 9. Precipitation of strengthening β-Mg2Si i θ'-Al2Cu phases in AlSi5Cu1Mg (a,b) – TEM

consisting of Al, Si, Mn and Fe (Fig. 2,7 and Tab. 3).

precipitates of hardening phase β-Mg2Si (Fig. 8) and θ′-Al2Cu (Fig. 9).

(a) (b)

Fig. 10. X-diffraction pattern of AlSi5Cu1Mg alloy

(a) (b)

(c) (d)

Fig. 11. SEM micrographs (a-d) of the particles extracted from the AlSi5Cu1Mg alloy and EDS spectra (e,f)

Intermetallic Phases Examination in Cast AlSi5Cu1Mg and

AlMnFeSi, Al5FeSi, Al5Mg8Cu2Si6 phases.

were shifted to the lower values (Fig. 12b).

AlCu4Ni2Mg2 alloy, at a heating rate 5°C/min

investigation presented in Tab. 5.

AlCu4Ni2Mg2 Aluminium Alloys in As-Cast and T6 Condition 33

The results of XRD investigation are shown in Fig. 8. X-ray diffraction analysis of AlSi1MgMn alloy confirmed metalograffic observation. Additionaly the presented above results were compared to the analysis of the particles extracted from the AlSi5Cu1Mg alloy using phenolic dissolution technique (Fig. 11). The EDS spectra revealed the presence of Al, Mg, Mn, Si, Fe and Cu - bearing particles in the extracted powder (Fig. 11). The EDS analysis results proof that analyzed particles extracted from the AlSi5Cu1Mg alloy were: Si,

DSC curves obtained by heating (Fig. 12a) and cooling (Fig. 12b) of as-cast specimens of AlCu4Ni2Mg2 alloy are shown in Fig. 12. DSC curves demonstrate reactions which occurred during heating and solidification process of the alloy. The obtained results were similar to the peaks observed during cooling of the samples of AlSi5Cu1Mg alloy – the recorded peaks

The solidification sequence of this alloy can be quite complex and dependent upon the cooling rate (Fig. 12). Possible reactions which occurred during solidification of AlCu4Ni2Mg2 alloy are presented in Tab. 5. Aluminum reach (α-Al) dendrites are formed at the beginning of solidification process. Additional alloying elements into the alloys (Ni, Cu, Mg) as well as impurities (eg. Fe) change the solidification path and reaction products. Therefore, as-cast microstructure of the tested alloy exhibit the appearance of mixture of intermetallic phases (Fig. 13a). The solidification reactions (the exact value of temperature) obtained during DSC

Possible reactions Temperature, °C

Table 5. Possible solidification reactions during nonequilibrium conditions in investigated

Fig. 13. The microstructure of AlCu4Ni2Mg2 alloy in as-cast state (a) and the T6 condition (b)

L→ (Al) + Al6Fe 612 L→ (Al) + Al4CuMg 584 L→(Al)+Al2Cu+Al2CuMg 558 L→(Al)+Al2Cu+Al7Cu4Ni 542 L→(Al)+Al2Cu+ Al2CuMg +Al3(CuFeNi)2 493 Solidus 480

(a) (b)

Fig. 12. DSC thermograms of as-cast specimens of AlCu4Ni2Mg2 alloy, obtained during a) heating and b) cooling at a rate of 5°C/min

250 300 350 400 450 500 550 600 650

Temperature, °C

(a)

250 300 350 400 450 500 550 600 650

Temperature°C

(b)

Fig. 12. DSC thermograms of as-cast specimens of AlCu4Ni2Mg2 alloy, obtained during

**1**

**2**

**6**

**5**

**6**

**5**

**4**

**3**

**4**

**3**

**2**

**1**





Exo

q = 5°C/min

a) heating and b) cooling at a rate of 5°C/min

Heat flow,

μ

V

0

3


Heat flow,

μ

V


Endo

q = 5°C/min


The results of XRD investigation are shown in Fig. 8. X-ray diffraction analysis of AlSi1MgMn alloy confirmed metalograffic observation. Additionaly the presented above results were compared to the analysis of the particles extracted from the AlSi5Cu1Mg alloy using phenolic dissolution technique (Fig. 11). The EDS spectra revealed the presence of Al, Mg, Mn, Si, Fe and Cu - bearing particles in the extracted powder (Fig. 11). The EDS analysis results proof that analyzed particles extracted from the AlSi5Cu1Mg alloy were: Si, AlMnFeSi, Al5FeSi, Al5Mg8Cu2Si6 phases.

DSC curves obtained by heating (Fig. 12a) and cooling (Fig. 12b) of as-cast specimens of AlCu4Ni2Mg2 alloy are shown in Fig. 12. DSC curves demonstrate reactions which occurred during heating and solidification process of the alloy. The obtained results were similar to the peaks observed during cooling of the samples of AlSi5Cu1Mg alloy – the recorded peaks were shifted to the lower values (Fig. 12b).

The solidification sequence of this alloy can be quite complex and dependent upon the cooling rate (Fig. 12). Possible reactions which occurred during solidification of AlCu4Ni2Mg2 alloy are presented in Tab. 5. Aluminum reach (α-Al) dendrites are formed at the beginning of solidification process. Additional alloying elements into the alloys (Ni, Cu, Mg) as well as impurities (eg. Fe) change the solidification path and reaction products. Therefore, as-cast microstructure of the tested alloy exhibit the appearance of mixture of intermetallic phases (Fig. 13a). The solidification reactions (the exact value of temperature) obtained during DSC investigation presented in Tab. 5.


Table 5. Possible solidification reactions during nonequilibrium conditions in investigated AlCu4Ni2Mg2 alloy, at a heating rate 5°C/min

Fig. 13. The microstructure of AlCu4Ni2Mg2 alloy in as-cast state (a) and the T6 condition (b)

Intermetallic Phases Examination in Cast AlSi5Cu1Mg and

**Suggested type of** 

20 Al7Cu4Ni

25 Al3(CuFeNi)2

**No. of analyzed particles**

AlCu4Ni2Mg2 alloy

AlCu4Ni2Mg2 Aluminium Alloys in As-Cast and T6 Condition 35

Fig. 15. a) SEM micrographs of the AlCu4Ni2Mg2 alloy in the T6 condition; b) The corresponding EDS-spectra acquired in positions indicated by the number 1 and 2

> 11.8÷22.2 18.08 14.2÷22.6

> 18÷22 17.1÷20.5

Table 6. The chemical composition and volume fraction of the intermetallic phases in the

Fig. 16. TEM micrograph of AlCu4Ni2Mg2 alloy in T6 conditions showing the precipitate of

the S-Al2CuMg phase (a,b), and corresponding electron diffraction pattern (c)

12 Al2Cu 52.5

**phases Ni Cu Fe** 

**Chemical composition of determined intermetallic phases, (%at)** 

> 38.7÷50.7 34.33 29.7÷45.2

> 9÷15 10.5÷19.3

> 47.7÷51.9

8÷10 7.2÷9.5 **Reference** 

Belov, 2005 Chen, 2010 This work

Belov, 2002 This work

Belov, 2005 This work

The analyzed microstructure in as- cast state (Fig. 13a) contains of primary aluminium dendrites and substantial amount of different intermetallic phases constituents varied in shape, size and distribution. They are located at the grain boundaries of α-Al and form dendrites network structure (Fig. 13a).

The analyzed microstructure of investigated AlCu4Ni2Mg2 alloy in T6 condition (Fig. 13b) consists different precipitates varied in shape, i.e.: fine sphere-like, complex rod-like and ellipse-like distributed within interdendritic areas of the α-Al alloy. Large number of fine sphere-like strengthening phase are located in the boundary zone. However, small volume of this phase is also present homogenously throughout the sample (Fig. 13b). In order to identify the intermetallic phases in the examined alloy, series of distribution maps were performed for the elements line Mg-K, Al-K, Fe-K, Ni-K, Cu-K (Fig. 14). The maximum pixel spectrum clearly shows the presence of Ni and Cu in the scanned microstructure. In order to identify the presence of the elements in the observed phases, two regions of the mapped phase with high nickel and copper concentration were marked and their spectra evaluated.

Fig. 14. SEM image of the AlCu4Ni2Mg2 alloy and corresponding elemental maps of: Al, Mg, Fe, Ni and Cu

As seen in the elemental maps in Fig. 14, the regions enriched in Ni and Cu correspond to the formation of type precipitates (complex rod-like) and ellipse-like precipitates observed in Fig. 13. Fig. 15 shows the scanning electron micrographs and EDS analysis of particles in the AlCu4Ni2Mg2 alloy.

The EDS analysis performed on the phases present in microstructure of the alloy revealed, that complex rod-like phase is the Al7Cu4Ni one, whereas the ellipse-like is Al3(CuFeNi)2 (Fig. 15 and Tab. 6)

The analyzed microstructure in as- cast state (Fig. 13a) contains of primary aluminium dendrites and substantial amount of different intermetallic phases constituents varied in shape, size and distribution. They are located at the grain boundaries of α-Al and form

The analyzed microstructure of investigated AlCu4Ni2Mg2 alloy in T6 condition (Fig. 13b) consists different precipitates varied in shape, i.e.: fine sphere-like, complex rod-like and ellipse-like distributed within interdendritic areas of the α-Al alloy. Large number of fine sphere-like strengthening phase are located in the boundary zone. However, small volume of this phase is also present homogenously throughout the sample (Fig. 13b). In order to identify the intermetallic phases in the examined alloy, series of distribution maps were performed for the elements line Mg-K, Al-K, Fe-K, Ni-K, Cu-K (Fig. 14). The maximum pixel spectrum clearly shows the presence of Ni and Cu in the scanned microstructure. In order to identify the presence of the elements in the observed phases, two regions of the mapped phase with high nickel and copper concentration were marked and their spectra evaluated.

dendrites network structure (Fig. 13a).

Mg, Fe, Ni and Cu

the AlCu4Ni2Mg2 alloy.

(Fig. 15 and Tab. 6)

Fig. 14. SEM image of the AlCu4Ni2Mg2 alloy and corresponding elemental maps of: Al,

As seen in the elemental maps in Fig. 14, the regions enriched in Ni and Cu correspond to the formation of type precipitates (complex rod-like) and ellipse-like precipitates observed in Fig. 13. Fig. 15 shows the scanning electron micrographs and EDS analysis of particles in

**Ni Fe Mg** 

**Al Cu**

The EDS analysis performed on the phases present in microstructure of the alloy revealed, that complex rod-like phase is the Al7Cu4Ni one, whereas the ellipse-like is Al3(CuFeNi)2

Fig. 15. a) SEM micrographs of the AlCu4Ni2Mg2 alloy in the T6 condition; b) The corresponding EDS-spectra acquired in positions indicated by the number 1 and 2


Table 6. The chemical composition and volume fraction of the intermetallic phases in the AlCu4Ni2Mg2 alloy

Fig. 16. TEM micrograph of AlCu4Ni2Mg2 alloy in T6 conditions showing the precipitate of the S-Al2CuMg phase (a,b), and corresponding electron diffraction pattern (c)

Intermetallic Phases Examination in Cast AlSi5Cu1Mg and

(a) (b)

(c) (d)

Ni Cu

(e) (f)

Cu

Fig. 19. SEM micrographs of the particles Al7Cu4Ni (a,c) and Al3(CuFeNi)2 (b,d) extracted

Fig. 20. The X-ray diffraction from the particles extracted from AlCu4Ni2Mg2 alloy

Energy, keV

from the AlCu4Ni2Mg2 alloy along with EDS spectra (e,f)

Cu Ni

Ni

Al

Intensity

AlCu4Ni2Mg2 Aluminium Alloys in As-Cast and T6 Condition 37

Ni

Al

Cu

Fe

Energy, keV

Fe Fe

Ni Ni

Cu Cu

Intensity

2 4 6 8 10 2 4 6 8 10

The microstructure of the examined alloy AlCu4Ni2Mg2 in T6 state consists of the primary precipitates of intermetallic phases combined with the highly dispersed particles of hardening phases. The TEM micrographs and the selected area electron diffraction patterns analysis proved that the dispersed precipitates shown in Fig. 13b are the intermetallic phases S-Al2CuMg (Fig. 16) and Al6Fe (Fig. 17) besides the precipitates of hardening phase θ′-Al2Cu were present in AlCu4Ni2Mg2 alloy (Fig. 18). The approximate size of the S phase was 0,5 μm.

Fig. 17. TEM micrograph of AlCu4Ni2Mg alloy in T6 condition showing the precipitate of the Al6Fe phase (a), and corresponding electron diffraction pattern (b)

Fig. 18. TEM micrograph of AlCu4Ni2Mg alloy in T6 condition showing the precipitates of hardening phase θ'-Al2Cu, bright field (a) and dark field (b)

The results of the SEM/EDS analysis of the particles extracted with boiling phenol from AlCu4Ni2Mg2 alloy (Fig. 19) were compared with X-ray diffraction pattern (Fig. 20). The observed peaks confirmed SEM and TEM results. The majority of the peaks were from Al7Cu4Ni, Al6Fe, S-Al2CuMg, and Al3(CuFeNi)2.

On the other hand, it is nearly impossible to make unambiguous identification of the all intermetallics present in an aluminium alloy which are rather complex, even applying all well-known experimental techniques. X-ray diffraction analysis is one of the most powerful and appropriate technique giving the possibility to determine most of verified intermetallics based on their crystallographic parameters. Our analysis shows that the difficulties of having reliable results of all the possible existing phases in a microstructure of the alloy is related to the procedure of phase isolation. The residue is separated by centrifuging and since some of the particles are very fine and available sieves are having too big outlet holes there is no chance prevents them from being flowing out from a solution.

Intensity

36 Recent Trends in Processing and Degradation of Aluminium Alloys

The microstructure of the examined alloy AlCu4Ni2Mg2 in T6 state consists of the primary precipitates of intermetallic phases combined with the highly dispersed particles of hardening phases. The TEM micrographs and the selected area electron diffraction patterns analysis proved that the dispersed precipitates shown in Fig. 13b are the intermetallic phases S-Al2CuMg (Fig. 16) and Al6Fe (Fig. 17) besides the precipitates of hardening phase θ′-Al2Cu were present in AlCu4Ni2Mg2 alloy (Fig. 18). The approximate size of the S phase

 Fig. 17. TEM micrograph of AlCu4Ni2Mg alloy in T6 condition showing the precipitate of

 Fig. 18. TEM micrograph of AlCu4Ni2Mg alloy in T6 condition showing the precipitates of

The results of the SEM/EDS analysis of the particles extracted with boiling phenol from AlCu4Ni2Mg2 alloy (Fig. 19) were compared with X-ray diffraction pattern (Fig. 20). The observed peaks confirmed SEM and TEM results. The majority of the peaks were from

On the other hand, it is nearly impossible to make unambiguous identification of the all intermetallics present in an aluminium alloy which are rather complex, even applying all well-known experimental techniques. X-ray diffraction analysis is one of the most powerful and appropriate technique giving the possibility to determine most of verified intermetallics based on their crystallographic parameters. Our analysis shows that the difficulties of having reliable results of all the possible existing phases in a microstructure of the alloy is related to the procedure of phase isolation. The residue is separated by centrifuging and since some of the particles are very fine and available sieves are having too big outlet holes

there is no chance prevents them from being flowing out from a solution.

the Al6Fe phase (a), and corresponding electron diffraction pattern (b)

hardening phase θ'-Al2Cu, bright field (a) and dark field (b)

Al7Cu4Ni, Al6Fe, S-Al2CuMg, and Al3(CuFeNi)2.

was 0,5 μm.

Fig. 19. SEM micrographs of the particles Al7Cu4Ni (a,c) and Al3(CuFeNi)2 (b,d) extracted from the AlCu4Ni2Mg2 alloy along with EDS spectra (e,f)

Fig. 20. The X-ray diffraction from the particles extracted from AlCu4Ni2Mg2 alloy

Intermetallic Phases Examination in Cast AlSi5Cu1Mg and

Inc, New York, ISBN 0-415-27352-8

*Characerisation*, No. 49, pp. 193-202

No. 18, pp 1750-1757

Oxford, Anglia

No. 17A, pp. 45-52

129

Ohio, ISBN 0-87170-176-6

No. 160, pp. 138-147

Brisbane, Toronto

alloys, *Acta Materialia*, No. 53 pp.4709–4722

*Manufacturing Engineering*, Vol. 24, No.2, pp. 51-54

AlCu4Ni2Mg2 Aluminium Alloys in As-Cast and T6 Condition 39

Belov, N.A., Aksenov, A.A. & Eskin, D.G. (2002). Iron in aluminium alloys, Taylor & Francis

Belov, N.A., Eskin, D.G. & Avxentieva, N.N. (2005). Constituent phase diagrams of the Al–

Cabibbo, M., Spigarelli, S. & Evangelista, E. (2003). A TEM investigation on the effect of

Chen, C.L. & Thomson, R.C. (2010). Study of thermal expansion of intermetallics in

Christian, J.W. (1995). The theory of transformations in metals and alloys. Pergamon Press,

Dobrzański, L.A., Maniara, R. & Sokolooki, J.H. (2007). Microstructure and mechanical

Garcia-Hinojosa, J.A., González, C.R., González, G.M. & Houbaert, Y. (2003). Structure and

Griger, A. & Stefaniay V. (1996). Equilibrium and non-equilibrium intermetallic phases in Al-Fe and Al-Fe-Si alloys, *Journal of Materials Science*, No. 31, pp. 6645-6652 Hatch, J.E (1984). Aluminium. Properties and Physical Metallurgy. Ed.., ASM Metals Park,

Ji, Y. Guo, F. & Pan, Y. (2008). Microstructural characteristics and paint-bake response of

Karabay, S., Yilmaz, M. & Zeren, M. (2004). Investigation of extrusion ratio effect on

King, F. (1987). Aluminium and its alloys. John Willey and Sons, New York, Chichester,

Kuijpers, N.C.W., Kool, W.H. & van der Zwaag, S. (2002). DSC study on Mg-Si phases in as

Li, Z., Samuel, A.M., Samuel, F.H., Ravindran, C., Valtierra, S. & Doty, H.W. (2004).

Liu, Y.L. Kang, S.B. &. Kim, H.W. (1999). The complex microstructures in as-cast Al-Mg-Si

Lodgaard, L. & Ryum, N. (2000). Precipitation of dispersoids containing Mn and/or Cr in Al-Mg-Si alloys, *Materials Since and Engineering A*, No.283, pp. 144-152

cast AA6xxx. *Mater. Sci. Forum,* No. 396-402, pp. 675-680

alloy, *Materials Letters,* No. 41, pp. 267-272

properties, *Materials Science and Engineering*, No. 367, pp. 96-110

Sr, *Journal of Materials Processing Technology*, No. 143–144, pp. 306–310 Gupta, A.K., Lloyd, D.J. & Court S.A. (2001). Precipitation hardening in Al-Mg-Si alloys with and without excess Si. *Materials Science and Engineering A*, No. 316, pp. 11-17 Gustafsson, G., Thorvaldsson, T. & Dunlop, G.L. (1986). The influence of Fe and Cr on the

Cu–Fe–Mg–Ni–Si system and their application to the analysis of aluminium piston

semisolid forming on precipitation processes in an Al-Mg-Si alloy, *Materials* 

multicomponent Al-Si alloys by high temperature X-ray diffraction, *Intermetallics*,

properties of AC AlSi9CuX alloys, *Journal of Achievements in Materials and* 

properties of Al–7Si–Ni and Al–7Si–Cu cast alloys nonmodied and modied with

microstructure of cast Al-Mg-Si alloys, *Metallurgical and Materials Transactions. A*,

Al-Mg-Si-Cu alloy, *Transactions of Nonferrous Metals Society of China*, No.18, pp. 126-

mechanical behaviour of extruded alloy AA-6101 from the billets homogenisedrapid quenched and as-cast conditions. *Journal of Materials Processing Technology,*

Parameters controlling the performance of AA319-type alloys Part I. Tensile
