3D characterization of microstructure evolution of cast AlMgSi alloys by synchrotron tomography
Effect of ECAP on microstructure and mechanical properties of cast
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Journal of Physics: Conference Series OPEN ACCESS Effect of ECAP on microstructure and mechanical properties of cast AZ91 magnesium alloy To cite this article: C W Chung et al 2010 J. Phys.: Conf. Ser. 241 012101 View the article online for updates and enhancements. You may also like Texture and microstructure evolution of A390 aluminum alloy during ECAP Esmaeil Damavandi, Salman Nourouzi, Sayed Mahmood Rabiee et al. - On the wear behavior of AA6061 alloy and in-situ AA6061-TiB 2 composite subjected to Equal Channel Angular Pressing Chidambaram A, A S Vivekananda, Balasivanandha Prabu Shanmugavel et al. - Effect of ECAP die angle to the microstructure and mechanical properties of bulk nanostructured Al-6061 Z S Zahari, D N Awang Sh’ri, M A H Abu Hassan et al. - This content was downloaded from IP address 192.140.30.240 on 01/02/2022 at 20:55
Transcript of Effect of ECAP on microstructure and mechanical properties of cast
Journal of Physics Conference Series
OPEN ACCESS
Effect of ECAP on microstructure and mechanicalproperties of cast AZ91 magnesium alloyTo cite this article C W Chung et al 2010 J Phys Conf Ser 241 012101
View the article online for updates and enhancements
You may also likeTexture and microstructure evolution ofA390 aluminum alloy during ECAPEsmaeil Damavandi Salman NourouziSayed Mahmood Rabiee et al
-
On the wear behavior of AA6061 alloy andin-situ AA6061-TiB2 composite subjectedto Equal Channel Angular PressingChidambaram A A S VivekanandaBalasivanandha Prabu Shanmugavel et al
-
Effect of ECAP die angle to themicrostructure and mechanical propertiesof bulk nanostructured Al-6061Z S Zahari D N Awang Shrsquori M A H AbuHassan et al
-
This content was downloaded from IP address 19214030240 on 01022022 at 2055
Effect of ECAP on microstructure and mechanical properties of cast AZ91 magnesium alloy
C W Chung1 2 R G Ding2 Y L Chiu2 and W Gao1 1 Department of Chemical amp Materials Engineering University of Auckland New Zealand
2 School of Metallurgy and Materials University of Birmingham United Kingdom
Email ychiubhamacuk
Abstract An as-cast AZ91 magnesium alloy was processed by Equal Channel Angular Pressing (ECAP) at 320degC The microstructure and mechanical properties were studied It has been found that ECAP refines both the grains and precipitates thus modifies the strength and ductility of the processed alloy After the first pass of ECAP the yield stress improves significantly from 71 MPa to 140 MPa
1 Introduction Magnesium casting alloys such as Mg-9Al-1Zn (AZ91) have attracted increasing attention from the automotive aircraft and electronic industries because of its low density high damping properties excellent machining abilities and good recycling potentials [1] However at room temperature as-cast AZ91 exhibits poor formability and limited ductility due to the high fraction of coarse Mg17Al12 intermetallic phase [2] Conventionally grain refinement is usually used in improving the strength and ductility of alloys Studies have shown that severe plastic deformation such as ECAP can improve the strength and ductility of processed materials by significantly reducing the grain size [3-6] The ECAP processing of the AZ91 alloy has been extensively investigated at high temperature and with solution treatment prior to ECAP to dissolve the coarse intermetallic particles In this study ECAP was carried out directly on an as-cast AZ91 The mechanical properties and microstructure before and after the ECAP have been investigated
2 Experimental Procedures A sand-cast ingot of AZ91 magnesium alloy with nominal chemical composition of 9 wt Al 1 wt Zn and 05 wt Mn was used in this study ECAP experiments were performed in a die with 90deg internal angle at 320degC and 4 mmmin pressing speed via the BC route [7] Tensile specimens with gauge dimensions of 2 2 75 mm3 were machined from the ECAP processed sample with the tensile axis parallel to the extrusion direction Tensile tests were carried out at room temperature at a nominal strain rate of 5 10-4 s-1 The microstructure observations were carried out on a JEOL 7000F FEGSEM and an FEI Tecnai F20 TEM equipped with an Oxford Instrument EDS system
Electron Microscopy and Analysis Group Conference 2009 (EMAG 2009) IOP PublishingJournal of Physics Conference Series 241 (2010) 012101 doi1010881742-65962411012101
ccopy 2010 Published under licence by IOP Publishing Ltd 1
3 Results
31 Microstructures Typical SEM micrographs of the as-cast and ECAP processed AZ91 are respectively shown in figure 1a-c Primary intermetallic phase (Mg17Al12) and eutectic product consisting of the intermetallic phase and -Mg are located at the interdendritic regions (figure 1a) The intermetallic particles with sizes of up to 80 m were observed After 1 pass of ECAP some of the large intermetallic phases and dendrites were broken and the grain size shows a bimodal distribution with the average size of about 8
m for the fine grains (figure 1b) The grain size remains at about 6 m with more than 2 passes of ECAP (figure 2) An EDS linescan across the matrix and part of particle (figure 3) indicates that the particle is Al and Zn rich The diffraction patterns in figures 3e and 3f confirmed the cubic nature of the particles which could be indexed as Mg17Al12 In addition a high density of dislocations was often observed in the matrix as shown in figure 4 Diffraction contrast analysis (not shown here) has indicated that most dislocations are ltagt type dislocations
Figure 1 Typical SEM micrographs of (a) as-cast (b) 1 ECAP pass and (c) 6 ECAP processed samples
32 Mechanical Properties Figure 5 shows the mechanical properties of the alloy as a function of number of ECAP passes After one pass of ECAP the strength improves significantly (ie the yield stress increased from 71 MPa to 140 MPa) while no obvious increase in ductility was observed After the second pass of ECAP the ductility of the alloy improved Further passes of ECAP shows no significant improvements in both the strength and elongation of the processed alloys
4 Discussions The tensile tests indicate that both the strength and ductility of as-cast AZ91 have been improved via ECAP processing The strengthening mechanisms in the ECAP processed alloy mainly include solid
Figure 2 Variation in grain size with the number of ECAP passes Note In 1 passed sample the size of
large grains were not included
Electron Microscopy and Analysis Group Conference 2009 (EMAG 2009) IOP PublishingJournal of Physics Conference Series 241 (2010) 012101 doi1010881742-65962411012101
2
solution strengthening precipitate strengthening and grain boundary strengthening The lack of peak shifts in X-ray diffraction experiments (not shown here) suggested that ECAP processing has no effect on the lattice parameters of both the matrix and the precipitates indicating that the ECAP has not modified the solid solution strengthening On the other hand precipitate (beta phase) strengthening depends on the chemistry volume fraction size morphology and distribution of the precipitates The constant lattice parameters upon the ECAP processing suggest that the chemistry of the precipitates has not been changed After 6 passes of ECAP the precipitate size has been refined to about 1 m which is not expected to provide an obvious strengthening Therefore precipitate strengthening is not expected to be the major strengthening Grain boundary strengthening is usually described by Hall-Petch equation The grain size of AZ91 alloy has been significantly refined by ECAP (ie 300 μm for the as-cast sample vs 6 μm for the 6-pass processed sample) The Hall-Petch coefficient for Mg was reported to be about 07 MPa m-12 for coarse grains (30-87 μm) and 013 MPa m12 for fine grains (17-30 μm) [8] If the coefficient is regarded to be 013 MPa m12 the contribution of grain boundary strengthening to the improvement of strength in the 6-pass sample is about 44 MPa It seems likely that grain boundary strengthening is the major strengthening factor in these ECAP processed alloys Consistently beyond 2 passes of ECAP the strength of AZ91 alloy has not been improved by the ECAP processing as no further grain size refinement was observed
(a)
(b)
(c)
(d)
(e)
(f)
Figure 3 A BF STEM image of the intermetallic particle in the as-cast alloy (a) EDS linescan across matrix and the particle illustrate the contraction changes of Mg (b) Al (c) and Zn (d)
Diffraction patterns obtained along [001] (e) and [011] (f) of the particle
Electron Microscopy and Analysis Group Conference 2009 (EMAG 2009) IOP PublishingJournal of Physics Conference Series 241 (2010) 012101 doi1010881742-65962411012101
3
5 Summary The ECAP effectively refines the grains and beta phase of AZ91 alloy thus improves the strength and ductility of AZ91 alloy Grain boundary strengthening is the major strengthening mechanism the ECAP processed alloy
References [1] Kainer U 2003 Magnesium ndash Alloys and Technologies (Weinheim Wiley-VCH) [2] Chen B Lin D L Li J Zeng X Q and Lu C 2007 Mater Sci Eng A 483-484 113-116 [3] Kim J K Jeong H G Hong S I Kim Y S and Kim W J 2001 Scr Mater 45 901-907 [4] Kim W J Chung C S Ma D S Hong S I and Kim H K 2003 Scr Mater 49 333-338 [5] Kocich R Greger M and Machackova A 2006 J Achieve Mater Manufacturing Eng 18 295-
298 [6] Valiev R Z and Langdon T G 2006 Prog Mater Sci 51 881-981 [7] Langdon T G 2007 Mater Sci Eng A 462 3-11 [8] Koike J 2005 Metall Mater Trans A 36 1689-96
(a)
(b)
Figure 4 A BF TEM image taken from 6- passed sample showing a high density of
dislocations
Figure 5 (a) True stress - true strain curves measured at room temperature from the as-cast and ECAP processed
samples with 1 2 and 6 passes (b) Variation in yield strength (YS) and ultimate tensile strength (UTS) with the
number of pass
Electron Microscopy and Analysis Group Conference 2009 (EMAG 2009) IOP PublishingJournal of Physics Conference Series 241 (2010) 012101 doi1010881742-65962411012101
4
Effect of ECAP on microstructure and mechanical properties of cast AZ91 magnesium alloy
C W Chung1 2 R G Ding2 Y L Chiu2 and W Gao1 1 Department of Chemical amp Materials Engineering University of Auckland New Zealand
2 School of Metallurgy and Materials University of Birmingham United Kingdom
Email ychiubhamacuk
Abstract An as-cast AZ91 magnesium alloy was processed by Equal Channel Angular Pressing (ECAP) at 320degC The microstructure and mechanical properties were studied It has been found that ECAP refines both the grains and precipitates thus modifies the strength and ductility of the processed alloy After the first pass of ECAP the yield stress improves significantly from 71 MPa to 140 MPa
1 Introduction Magnesium casting alloys such as Mg-9Al-1Zn (AZ91) have attracted increasing attention from the automotive aircraft and electronic industries because of its low density high damping properties excellent machining abilities and good recycling potentials [1] However at room temperature as-cast AZ91 exhibits poor formability and limited ductility due to the high fraction of coarse Mg17Al12 intermetallic phase [2] Conventionally grain refinement is usually used in improving the strength and ductility of alloys Studies have shown that severe plastic deformation such as ECAP can improve the strength and ductility of processed materials by significantly reducing the grain size [3-6] The ECAP processing of the AZ91 alloy has been extensively investigated at high temperature and with solution treatment prior to ECAP to dissolve the coarse intermetallic particles In this study ECAP was carried out directly on an as-cast AZ91 The mechanical properties and microstructure before and after the ECAP have been investigated
2 Experimental Procedures A sand-cast ingot of AZ91 magnesium alloy with nominal chemical composition of 9 wt Al 1 wt Zn and 05 wt Mn was used in this study ECAP experiments were performed in a die with 90deg internal angle at 320degC and 4 mmmin pressing speed via the BC route [7] Tensile specimens with gauge dimensions of 2 2 75 mm3 were machined from the ECAP processed sample with the tensile axis parallel to the extrusion direction Tensile tests were carried out at room temperature at a nominal strain rate of 5 10-4 s-1 The microstructure observations were carried out on a JEOL 7000F FEGSEM and an FEI Tecnai F20 TEM equipped with an Oxford Instrument EDS system
Electron Microscopy and Analysis Group Conference 2009 (EMAG 2009) IOP PublishingJournal of Physics Conference Series 241 (2010) 012101 doi1010881742-65962411012101
ccopy 2010 Published under licence by IOP Publishing Ltd 1
3 Results
31 Microstructures Typical SEM micrographs of the as-cast and ECAP processed AZ91 are respectively shown in figure 1a-c Primary intermetallic phase (Mg17Al12) and eutectic product consisting of the intermetallic phase and -Mg are located at the interdendritic regions (figure 1a) The intermetallic particles with sizes of up to 80 m were observed After 1 pass of ECAP some of the large intermetallic phases and dendrites were broken and the grain size shows a bimodal distribution with the average size of about 8
m for the fine grains (figure 1b) The grain size remains at about 6 m with more than 2 passes of ECAP (figure 2) An EDS linescan across the matrix and part of particle (figure 3) indicates that the particle is Al and Zn rich The diffraction patterns in figures 3e and 3f confirmed the cubic nature of the particles which could be indexed as Mg17Al12 In addition a high density of dislocations was often observed in the matrix as shown in figure 4 Diffraction contrast analysis (not shown here) has indicated that most dislocations are ltagt type dislocations
Figure 1 Typical SEM micrographs of (a) as-cast (b) 1 ECAP pass and (c) 6 ECAP processed samples
32 Mechanical Properties Figure 5 shows the mechanical properties of the alloy as a function of number of ECAP passes After one pass of ECAP the strength improves significantly (ie the yield stress increased from 71 MPa to 140 MPa) while no obvious increase in ductility was observed After the second pass of ECAP the ductility of the alloy improved Further passes of ECAP shows no significant improvements in both the strength and elongation of the processed alloys
4 Discussions The tensile tests indicate that both the strength and ductility of as-cast AZ91 have been improved via ECAP processing The strengthening mechanisms in the ECAP processed alloy mainly include solid
Figure 2 Variation in grain size with the number of ECAP passes Note In 1 passed sample the size of
large grains were not included
Electron Microscopy and Analysis Group Conference 2009 (EMAG 2009) IOP PublishingJournal of Physics Conference Series 241 (2010) 012101 doi1010881742-65962411012101
2
solution strengthening precipitate strengthening and grain boundary strengthening The lack of peak shifts in X-ray diffraction experiments (not shown here) suggested that ECAP processing has no effect on the lattice parameters of both the matrix and the precipitates indicating that the ECAP has not modified the solid solution strengthening On the other hand precipitate (beta phase) strengthening depends on the chemistry volume fraction size morphology and distribution of the precipitates The constant lattice parameters upon the ECAP processing suggest that the chemistry of the precipitates has not been changed After 6 passes of ECAP the precipitate size has been refined to about 1 m which is not expected to provide an obvious strengthening Therefore precipitate strengthening is not expected to be the major strengthening Grain boundary strengthening is usually described by Hall-Petch equation The grain size of AZ91 alloy has been significantly refined by ECAP (ie 300 μm for the as-cast sample vs 6 μm for the 6-pass processed sample) The Hall-Petch coefficient for Mg was reported to be about 07 MPa m-12 for coarse grains (30-87 μm) and 013 MPa m12 for fine grains (17-30 μm) [8] If the coefficient is regarded to be 013 MPa m12 the contribution of grain boundary strengthening to the improvement of strength in the 6-pass sample is about 44 MPa It seems likely that grain boundary strengthening is the major strengthening factor in these ECAP processed alloys Consistently beyond 2 passes of ECAP the strength of AZ91 alloy has not been improved by the ECAP processing as no further grain size refinement was observed
(a)
(b)
(c)
(d)
(e)
(f)
Figure 3 A BF STEM image of the intermetallic particle in the as-cast alloy (a) EDS linescan across matrix and the particle illustrate the contraction changes of Mg (b) Al (c) and Zn (d)
Diffraction patterns obtained along [001] (e) and [011] (f) of the particle
Electron Microscopy and Analysis Group Conference 2009 (EMAG 2009) IOP PublishingJournal of Physics Conference Series 241 (2010) 012101 doi1010881742-65962411012101
3
5 Summary The ECAP effectively refines the grains and beta phase of AZ91 alloy thus improves the strength and ductility of AZ91 alloy Grain boundary strengthening is the major strengthening mechanism the ECAP processed alloy
References [1] Kainer U 2003 Magnesium ndash Alloys and Technologies (Weinheim Wiley-VCH) [2] Chen B Lin D L Li J Zeng X Q and Lu C 2007 Mater Sci Eng A 483-484 113-116 [3] Kim J K Jeong H G Hong S I Kim Y S and Kim W J 2001 Scr Mater 45 901-907 [4] Kim W J Chung C S Ma D S Hong S I and Kim H K 2003 Scr Mater 49 333-338 [5] Kocich R Greger M and Machackova A 2006 J Achieve Mater Manufacturing Eng 18 295-
298 [6] Valiev R Z and Langdon T G 2006 Prog Mater Sci 51 881-981 [7] Langdon T G 2007 Mater Sci Eng A 462 3-11 [8] Koike J 2005 Metall Mater Trans A 36 1689-96
(a)
(b)
Figure 4 A BF TEM image taken from 6- passed sample showing a high density of
dislocations
Figure 5 (a) True stress - true strain curves measured at room temperature from the as-cast and ECAP processed
samples with 1 2 and 6 passes (b) Variation in yield strength (YS) and ultimate tensile strength (UTS) with the
number of pass
Electron Microscopy and Analysis Group Conference 2009 (EMAG 2009) IOP PublishingJournal of Physics Conference Series 241 (2010) 012101 doi1010881742-65962411012101
4
3 Results
31 Microstructures Typical SEM micrographs of the as-cast and ECAP processed AZ91 are respectively shown in figure 1a-c Primary intermetallic phase (Mg17Al12) and eutectic product consisting of the intermetallic phase and -Mg are located at the interdendritic regions (figure 1a) The intermetallic particles with sizes of up to 80 m were observed After 1 pass of ECAP some of the large intermetallic phases and dendrites were broken and the grain size shows a bimodal distribution with the average size of about 8
m for the fine grains (figure 1b) The grain size remains at about 6 m with more than 2 passes of ECAP (figure 2) An EDS linescan across the matrix and part of particle (figure 3) indicates that the particle is Al and Zn rich The diffraction patterns in figures 3e and 3f confirmed the cubic nature of the particles which could be indexed as Mg17Al12 In addition a high density of dislocations was often observed in the matrix as shown in figure 4 Diffraction contrast analysis (not shown here) has indicated that most dislocations are ltagt type dislocations
Figure 1 Typical SEM micrographs of (a) as-cast (b) 1 ECAP pass and (c) 6 ECAP processed samples
32 Mechanical Properties Figure 5 shows the mechanical properties of the alloy as a function of number of ECAP passes After one pass of ECAP the strength improves significantly (ie the yield stress increased from 71 MPa to 140 MPa) while no obvious increase in ductility was observed After the second pass of ECAP the ductility of the alloy improved Further passes of ECAP shows no significant improvements in both the strength and elongation of the processed alloys
4 Discussions The tensile tests indicate that both the strength and ductility of as-cast AZ91 have been improved via ECAP processing The strengthening mechanisms in the ECAP processed alloy mainly include solid
Figure 2 Variation in grain size with the number of ECAP passes Note In 1 passed sample the size of
large grains were not included
Electron Microscopy and Analysis Group Conference 2009 (EMAG 2009) IOP PublishingJournal of Physics Conference Series 241 (2010) 012101 doi1010881742-65962411012101
2
solution strengthening precipitate strengthening and grain boundary strengthening The lack of peak shifts in X-ray diffraction experiments (not shown here) suggested that ECAP processing has no effect on the lattice parameters of both the matrix and the precipitates indicating that the ECAP has not modified the solid solution strengthening On the other hand precipitate (beta phase) strengthening depends on the chemistry volume fraction size morphology and distribution of the precipitates The constant lattice parameters upon the ECAP processing suggest that the chemistry of the precipitates has not been changed After 6 passes of ECAP the precipitate size has been refined to about 1 m which is not expected to provide an obvious strengthening Therefore precipitate strengthening is not expected to be the major strengthening Grain boundary strengthening is usually described by Hall-Petch equation The grain size of AZ91 alloy has been significantly refined by ECAP (ie 300 μm for the as-cast sample vs 6 μm for the 6-pass processed sample) The Hall-Petch coefficient for Mg was reported to be about 07 MPa m-12 for coarse grains (30-87 μm) and 013 MPa m12 for fine grains (17-30 μm) [8] If the coefficient is regarded to be 013 MPa m12 the contribution of grain boundary strengthening to the improvement of strength in the 6-pass sample is about 44 MPa It seems likely that grain boundary strengthening is the major strengthening factor in these ECAP processed alloys Consistently beyond 2 passes of ECAP the strength of AZ91 alloy has not been improved by the ECAP processing as no further grain size refinement was observed
(a)
(b)
(c)
(d)
(e)
(f)
Figure 3 A BF STEM image of the intermetallic particle in the as-cast alloy (a) EDS linescan across matrix and the particle illustrate the contraction changes of Mg (b) Al (c) and Zn (d)
Diffraction patterns obtained along [001] (e) and [011] (f) of the particle
Electron Microscopy and Analysis Group Conference 2009 (EMAG 2009) IOP PublishingJournal of Physics Conference Series 241 (2010) 012101 doi1010881742-65962411012101
3
5 Summary The ECAP effectively refines the grains and beta phase of AZ91 alloy thus improves the strength and ductility of AZ91 alloy Grain boundary strengthening is the major strengthening mechanism the ECAP processed alloy
References [1] Kainer U 2003 Magnesium ndash Alloys and Technologies (Weinheim Wiley-VCH) [2] Chen B Lin D L Li J Zeng X Q and Lu C 2007 Mater Sci Eng A 483-484 113-116 [3] Kim J K Jeong H G Hong S I Kim Y S and Kim W J 2001 Scr Mater 45 901-907 [4] Kim W J Chung C S Ma D S Hong S I and Kim H K 2003 Scr Mater 49 333-338 [5] Kocich R Greger M and Machackova A 2006 J Achieve Mater Manufacturing Eng 18 295-
298 [6] Valiev R Z and Langdon T G 2006 Prog Mater Sci 51 881-981 [7] Langdon T G 2007 Mater Sci Eng A 462 3-11 [8] Koike J 2005 Metall Mater Trans A 36 1689-96
(a)
(b)
Figure 4 A BF TEM image taken from 6- passed sample showing a high density of
dislocations
Figure 5 (a) True stress - true strain curves measured at room temperature from the as-cast and ECAP processed
samples with 1 2 and 6 passes (b) Variation in yield strength (YS) and ultimate tensile strength (UTS) with the
number of pass
Electron Microscopy and Analysis Group Conference 2009 (EMAG 2009) IOP PublishingJournal of Physics Conference Series 241 (2010) 012101 doi1010881742-65962411012101
4
solution strengthening precipitate strengthening and grain boundary strengthening The lack of peak shifts in X-ray diffraction experiments (not shown here) suggested that ECAP processing has no effect on the lattice parameters of both the matrix and the precipitates indicating that the ECAP has not modified the solid solution strengthening On the other hand precipitate (beta phase) strengthening depends on the chemistry volume fraction size morphology and distribution of the precipitates The constant lattice parameters upon the ECAP processing suggest that the chemistry of the precipitates has not been changed After 6 passes of ECAP the precipitate size has been refined to about 1 m which is not expected to provide an obvious strengthening Therefore precipitate strengthening is not expected to be the major strengthening Grain boundary strengthening is usually described by Hall-Petch equation The grain size of AZ91 alloy has been significantly refined by ECAP (ie 300 μm for the as-cast sample vs 6 μm for the 6-pass processed sample) The Hall-Petch coefficient for Mg was reported to be about 07 MPa m-12 for coarse grains (30-87 μm) and 013 MPa m12 for fine grains (17-30 μm) [8] If the coefficient is regarded to be 013 MPa m12 the contribution of grain boundary strengthening to the improvement of strength in the 6-pass sample is about 44 MPa It seems likely that grain boundary strengthening is the major strengthening factor in these ECAP processed alloys Consistently beyond 2 passes of ECAP the strength of AZ91 alloy has not been improved by the ECAP processing as no further grain size refinement was observed
(a)
(b)
(c)
(d)
(e)
(f)
Figure 3 A BF STEM image of the intermetallic particle in the as-cast alloy (a) EDS linescan across matrix and the particle illustrate the contraction changes of Mg (b) Al (c) and Zn (d)
Diffraction patterns obtained along [001] (e) and [011] (f) of the particle
Electron Microscopy and Analysis Group Conference 2009 (EMAG 2009) IOP PublishingJournal of Physics Conference Series 241 (2010) 012101 doi1010881742-65962411012101
3
5 Summary The ECAP effectively refines the grains and beta phase of AZ91 alloy thus improves the strength and ductility of AZ91 alloy Grain boundary strengthening is the major strengthening mechanism the ECAP processed alloy
References [1] Kainer U 2003 Magnesium ndash Alloys and Technologies (Weinheim Wiley-VCH) [2] Chen B Lin D L Li J Zeng X Q and Lu C 2007 Mater Sci Eng A 483-484 113-116 [3] Kim J K Jeong H G Hong S I Kim Y S and Kim W J 2001 Scr Mater 45 901-907 [4] Kim W J Chung C S Ma D S Hong S I and Kim H K 2003 Scr Mater 49 333-338 [5] Kocich R Greger M and Machackova A 2006 J Achieve Mater Manufacturing Eng 18 295-
298 [6] Valiev R Z and Langdon T G 2006 Prog Mater Sci 51 881-981 [7] Langdon T G 2007 Mater Sci Eng A 462 3-11 [8] Koike J 2005 Metall Mater Trans A 36 1689-96
(a)
(b)
Figure 4 A BF TEM image taken from 6- passed sample showing a high density of
dislocations
Figure 5 (a) True stress - true strain curves measured at room temperature from the as-cast and ECAP processed
samples with 1 2 and 6 passes (b) Variation in yield strength (YS) and ultimate tensile strength (UTS) with the
number of pass
Electron Microscopy and Analysis Group Conference 2009 (EMAG 2009) IOP PublishingJournal of Physics Conference Series 241 (2010) 012101 doi1010881742-65962411012101
4
5 Summary The ECAP effectively refines the grains and beta phase of AZ91 alloy thus improves the strength and ductility of AZ91 alloy Grain boundary strengthening is the major strengthening mechanism the ECAP processed alloy
References [1] Kainer U 2003 Magnesium ndash Alloys and Technologies (Weinheim Wiley-VCH) [2] Chen B Lin D L Li J Zeng X Q and Lu C 2007 Mater Sci Eng A 483-484 113-116 [3] Kim J K Jeong H G Hong S I Kim Y S and Kim W J 2001 Scr Mater 45 901-907 [4] Kim W J Chung C S Ma D S Hong S I and Kim H K 2003 Scr Mater 49 333-338 [5] Kocich R Greger M and Machackova A 2006 J Achieve Mater Manufacturing Eng 18 295-
298 [6] Valiev R Z and Langdon T G 2006 Prog Mater Sci 51 881-981 [7] Langdon T G 2007 Mater Sci Eng A 462 3-11 [8] Koike J 2005 Metall Mater Trans A 36 1689-96
(a)
(b)
Figure 4 A BF TEM image taken from 6- passed sample showing a high density of
dislocations
Figure 5 (a) True stress - true strain curves measured at room temperature from the as-cast and ECAP processed
samples with 1 2 and 6 passes (b) Variation in yield strength (YS) and ultimate tensile strength (UTS) with the
number of pass
Electron Microscopy and Analysis Group Conference 2009 (EMAG 2009) IOP PublishingJournal of Physics Conference Series 241 (2010) 012101 doi1010881742-65962411012101
4
