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High strain rate superplasticity of A1N particulate reinforced 1N90 pure aluminum composite
Scripta Metallursica et&t&&a,Vol. 33, No. 8, pp. 1333-1338.1995
Elsevk Scilncc Ltd chpyri&,o 1995 Acta Ivktdlucgica Inc. F’rmtedmtheUSAAUri&aresewed 09%-716x/95 $9.50 + .oo
Pergamon 0956-716X(95)00361-4
HIGH STRAIN RATE SUPERPLASTICITY OF AlN PARTICULATE REINFORCED lN90 PURE ALUMINUM COMPOSITE ‘IT.Imai*, G. L’Esperance**, B.D. Hong** and S. Kojima*** rCNational Industrial Research Institute of Nagoya, 1 Hirate-cho, Kita-ku, Nagoya 462, Japan ** Cole Polytechique de Montreal, P.O.Box 6079, Station”A”, Montreal (Quebec) H3C 3A7 Canada *** Nagoya Municipal Industrial Research Institute, 3-4-41 Rokuban-cho, Atsuta-ku, Nagoya 456, Japan (Received April 28,1995) (Revised June 2 1,1995) Introduction
Ceramic whisker or particulate reinforced aluminium alloy composites are attractive for application to automobile engineering components, aerospace structures, semi-conductor packaging and etc. since these composites exhibit excellent mechanical, physical and thermal properties and also superplasticity produced at high strain rate such as 0.1 - 10 S“ [l-l 0, 121 is expected to allow near-net shape forming of parts or structure components made of such materilas. An AIN particulate reinforced altuninium alloy composite exhibits a high elastic moduhts and a high thermal conductivity[l 11. Moreover, its thermal expansion is similar to silicon so that this composite is expected to apply to semi-conductor packaging in the aerospace structure. In addition, it was also found that the composite could produce superplasticity at high strain rates[ 121. But the super-plastic characteristics of the aluminium alloy composites has not yet been clear entirely. Superplastic det?ormationmechanisms of AlN particulate reinforced album alloy composites include grain boundary sliding[8], interfacial sliding with the presence of a liquid phase[8,9] and dynamic recrystalization, because a lot of experimental results demonstrated that strain rate sensitivity(m value) of superplasticmeti.manixcomposites[3-61 wasintherangeof0.3-0.5, whichshowsthatfinegrainboundary sliding is a predominant deformation mechanism. As AlN particulate reinforced alttminium alloy composite has a lot of interfaces, the superplasticdeformation mechanism should be di&rent from that of a conventional superplastic aluminium alloy. Therefore, it is important to make clear, experimentally, how grain boundary sliding could control HSRS, or ifinterfacial sliding at a liquid phase could occur during HSRS and if dynamic recrystalization c.an contribute to HSRS. The purpose of this study is to develop a thermomechanical processing route to produce a tine microstructure and to huther produce HSRS in a lN90 pure aluminium and in a AlN particulate reinforced lN90 pure aluminum composite. In addition, the superplastic characteristics of the composite and the pure alummium will also be discussed
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Vol. 33, No. 8
TABLE 1
ChemicalCompositionsof AlN ParticlesUsed as ReinforcementMaterial material
AIN
Fe
Si
cu
hQ
Ni
Cr
0
N
C
PPm 69
PPm 102
Ppm 5
PPm 14
Ppm 5
ppm 6
wt% 1.29
wt% 32.9
wt% 0.03
AlN particle (average particle size of 1.78~) was used as reinforcement material. Table 1 and 2 indicate chemical compositions of AlN particle and lN90 pure ahtminium(Japanese standard), respectively. AhWIN Al composite was sir&red under pressure of 200MPa at 773K for 20 minutes and extruded with the extrusion ratio of 44 at 773K. Thermomechanicalprocessing, includinghot extrusion and further hot rolling, was used to produce HSRS composite. Hot rolling was carried out at 913 or 923 K. Thickness reduction per each pass was less than 0.1 and the reheating time between each rolling passes was about 5 minutes. The final thickness of the hot-rolled composite was about 0.35-0.75mm. Tensile specimens with a 4 mm gage width and a 5.5 mm gage length were made. Test orientation was coincident with extruded and hot rolled directions. Specimens were pulled at 9 13 K and at strain rates ranging from 1 x 1v2 to 2 se1in constant crosshead speed. Flow stresses were determined by maximum flow stress in true stress-true strain curves. Microstructure and fracture surface of the samples were examined by TEM and SFM. Results and Discussion
Figure 1 (a) and (b) show the TEM microstructures (gram size) of (a) pure aluminium lN90 and (b) AlN/lN90 aluminiumcomposite hot-rolled and extruded. The gram sizes of pure ahnninium and AWIN Al composite are about 2pm. Therefore, the lN90 Al and the composite is expected to produce superplasticity at high strain rate. AlN particles were dispersed homogeneously in the hot-rolled A&J/l N90 Al composite as the particle size distribution of AlN is very narrow. Flow stress (a)and true strain rate g) in a superplastic material are related via the equation o = Ki m where K is a constant, and m is the strain rate sensitivity value. The m value of a super-plastic material is normally greater than 0.3 because a high m value is expected to suppress neck formation and leads to high tensile elongation. The relationships between the flow stress and the strain rate of the hot-rolled lN90 pure aluminum and AlN/lN90 Al composite as compared with that of AlN/6061 Al composite are shown in Fig. 2. Testing temperatum of lN90 pure Al and AlN/lN90 Al composite is 913K which is just below melting temperature of pure aluminium (93313). TABLE 2 Chemical material
IN90
Compositionsof lN90 Pure Aluminium
Fe
Cu
Si
Zn
Mn
Mg
Ti
ppm 43
ppm 6
ppm 41
ppm 17
ppm 5
ppm 3
ppm 2
Cr -
Ni
Al
ppm 3
wt% 99.99
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Vol. 33, No. 8
Figure 1. TEM microstructures of (a) lN90 pure ahuninium and (b) the AWlN90
Al omposite hot-rolled and exbuded,
The strain rate sensitivity value, m, of the AlNIlN90 Al composite hot-rolled at 923K &et- extrusion is about 0.3 in strain rate range from 0.05 s“ upto 0.2, although the m value of the AlN/6061 Al composite exhibits about 0.49. But the m value of lN90 pure ahrminium indicates also about 0.49 in the relatively low strain rate range from 0.005 up to 0.025 5-l.Therefore, it is shown that the lN90 pure ahuninium alone and the AlN/l N90 AI composite processed by hot-rolling after extrusion could produce the HSRS. Tensile elongations of the AlNIl N90, the AlN/606 1 Al composites [ 111,and 1N90 pure aluminium as a function of strain rate are shown in Fig. 3. The maximum tensile elongation of about 200% in the AlN/lN90 Al composite was obtained at strain rate range from about 0.1 s-r to 0.3 s“ and at 913K (below melting temperature), ahhough the IN90 pure aluminium alone shows the total elongation more than 200% at the relatively lower strain rate of about 0.015 6’ and at the same temperature. What is interesting in the AM/IN90 Al composite is that the optimum strain rate at which maximum total elongation is obtained is almost the same as that of the AM/606 1 Al composite. But, the AlN/606 1 Al composite still maintains the total elongation of 300% at the very high strain rate of 1.0 s-‘. On the other hand, in strain rates higher than 0.3 s-r, the elongation value of the AWlN90 Al composite begins to decrease as the m value becomes slightly low [ 131,
100
10
.i)ol
.Ol
.l Strain
1
10
rate (l/see)
Figure 2. Relationships between flow stress and strain rate ofthe AlN/IN90 Al composite and the lN90 pure aluminum extrudedand hot-rolled
HIGH STRAJN SUPERPLASTlCITY
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Vol. 33, No. 8
lN90 alone, AlNIlN90 land MN16061....................................! I
100 -Rolling ____-
teFP=-
0 l
A
;923K(AINllN90) ‘--;823K(lN90 alone) ;818K(AlN/6061) I
lo’ * ’ ***‘* .r101 .Ol
.1
1
CL.
10
Strain rate (llsec) Figure 3. Relationships between total elongation and strain rate of the lN90 pure ahminium, composites hot-rolled and extruded.
the AWlN90
and AM606 1 Al alloy
which indicates that void initiates in higher strain rate than 1.O 6’. A total elongation over 100% can be obtained in a wide strain rate range from 0.0 15 s-’ up to 0.9 s-’ in the AlN/lN90 Al composite. ‘EM observation in Fig. 1 shows that the grain sizes of the lN90 pure aluminium and the AlN/lN90 Al composite have almost the same size of 2pm, although optimum strain rate of the HSRS for the lN90 aluminium alone becomes lower at ten times than that of the AlN/l N90 Al composite. The results indicate
Energy
(keYI
Figure 4. EDS analysis at the interface and in the matrix for AlN2/1N90 Al composite hot-rolled a&r extrwim
Vol. 33, No. 8
HIGH STRAINSUPERPLASTIClTY
1337
Figure 5. Fracture surfaces ofthe AlN/lN90 aluminium alloy composite hot-rolled ad extruded. (a) is pulled at 0.049s”. The total elongstions of (a) is 1159%snd that of @) is 246”/4 respectively.
that hne grain size is a predominant factor to increase the optimum strain rate at which the HSRS occurs. The necessary condition to produce super-plasticityin conventional supetplastic al~umiums includes a fine and equaxial gram with a high angle gram boundary. Therefore, it is thought that the di&rence of the optimum strain rate in the HSRS between lN90 pure ahtminium alone and the AlN/lN90 Al composite might be related with a structure of the grain boundary such as high angle gram boundary. Magnesium and Copper segregations in the SiCJ6061, AlN/606 1, Si,N,w/2 124 and Si,N,w/7064 Al composites have been demonshand by L!Esperance et al. [9] and Imai et al. [lo] and it has been thought that an interfacial slidingwith the presence ofliquid phase is associated with solute segregation and eutectic phase formation at or near an interface between a matrix and a reinforcement in ahtminium ahoy composites reinforced by ceramic whiskers or particulates. But, EDS analysis of the AlN/lN90 Al composite in Fig.4 detects only ahmtinium and carbon at the interface between AlN particle and lN90 pure ahuninium matrix. The above results support the fact that primarily deformation mechanism of the HSRS of the 1N90 aluminium alone and the AlN/lN90 Al composite is grain boundary sliding, but the presence of a thin liquid phase probably might enhance the HSRS of AlN/6061 Al composite, The fracture surface of the AlN/lN90 Al composite contains a partially liquid phase and filament as shown in Fig. 5. The strain rates and the total elongations of the:AWlN90 composites are (a) 0.049 s “and 159%, and (b) 0.27 S’ and 246%, respectively. Conclusions
The super-plastic characteristics of lN90 pure aluminium alone and AlN/lN90 pure aluminum composite, fabricated by P/M method and hot-rolled after extrusion, were investigated. The following results were obtained:
(1) The strain rate sensitivity (m value) of the AlNIl N90 aluminum composites is about 0.3 and the total elongation of the composite become 1OO-200% in strain rate range from .02 up to 1.O s-’ and at 913K.
(2) The lN90 pure aluminumalone indicates the m value of about 0.45 and the total elongation of 200 % in strain rate range fi-om 0.002 8’ and at 913K. (3) Grain sizes of the IN90 pure aluminium alone and the AWlN90
Al composite aftersuper plastic defonnation are about 2pm. (4) EDS analys’isat the interface and on the matrix of the AUWlN90 pure aluminium composite indicates only ahuninium and carbon.
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HIGH STRAIN SUPERF’LASTICITY
Vol. 33, No. 8
(5) These results indicate that predominant deformation mechanism of the 1N90 purealuminium alone and
the AlNllN90 Al composite is a grain boundary sliding. References 1. 2. 3. 4. 5. 6. 7. 8 9. 10. 11. 12. 13.
14. 15.
T.G. Nieb, C.A. Henshall and J. Wadsworth, Scripta Metalhqica, 18-12(1984) 1405-1408 M.W. Mahoney and AK Ghcsh, Metall. Tram, 18A(1987) 653661 T. Imai, M.Mabuchi, Y. Tozawa and M. Yamada, JMatcrials Science letters, 9 (1990) 255-257 M. Mabuchi, T. I&, K. Kubo, H. Hi&i, Y. Okada and T. Tanimum, Materials Le.&x, 10 (1991) 339-342 M. Mabuchi, K H&&i, Y. Okada, S. Tanimum, T.ImaiaudK.Kubo,Scripta Meklhqica et Makrialia, 25 (1991)2517-2522 T. Imai. M. Mabuchi and T. Tozawa, Supcrpktkity in advanced materials edited by S.Hori,M.Tokizane and N.Fwushin$A Publication of JSRS,1991)373-378 T. Tsuzuku and A Takah&i, Proc. of 1st Japan Inkmational SAMPE Symposium (Nov.28~Deal, 1989)243. T.G. Nieh and J. Wadsworth, Supcrplasticity in Advanced Materiak edited by S. Hori, M. Tokizanc and N. Futushiro (A Publication of JSRS, 1991), 339-348 G. L’Ekpexance, T. hnai awl B.Hong. ibid, 379-384 T. hnai, G.L ‘L’Espgdnce, B. Hong. M. Mabuchi, and Y. Tozawa, Advances in Powder Metalhqy & Particulate Materials-1992 compiled by J.M. Caus and RM. German, 9 (1992)181-194 T. Imai, G.L ‘LEsperance & B.D. Hong, Scripta Mctallst Mater., (1994) in press S. Kem&a&$ FabrktiionofPattiadate Rcinked M&l Compositea, Edited by J. Masounave t F.G. Hamcl, (1990, Published by ASM Intcmational) 87-100. K H&a&i, T. Okada, T. Mukai, S. Tanimura, T.G. Nieh, and J. Wadsworth, inmlntl. Meeting on AdvancedMaterialsVoZ 7(IUMRSIW93, Sjmp. E, SuperpkWici~), edited by M. Doyama, S. Somiya, and RP.H. Chaq Pergamon Press, Nctherhmd (1993). inpress T.G. Nieh, J. Wadsworth, and T. hnai, Scripta Metall. Mater., 26 (1992) 55 l-556. M. Mabuchi, K H&a&i, Y. Okada, S. Tanimura, T. Imai, and K Kubo, Scripta Metall. Mater. 25 (1991) 2003-2006.
Elsevk Scilncc Ltd chpyri&,o 1995 Acta Ivktdlucgica Inc. F’rmtedmtheUSAAUri&aresewed 09%-716x/95 $9.50 + .oo
Pergamon 0956-716X(95)00361-4
HIGH STRAIN RATE SUPERPLASTICITY OF AlN PARTICULATE REINFORCED lN90 PURE ALUMINUM COMPOSITE ‘IT.Imai*, G. L’Esperance**, B.D. Hong** and S. Kojima*** rCNational Industrial Research Institute of Nagoya, 1 Hirate-cho, Kita-ku, Nagoya 462, Japan ** Cole Polytechique de Montreal, P.O.Box 6079, Station”A”, Montreal (Quebec) H3C 3A7 Canada *** Nagoya Municipal Industrial Research Institute, 3-4-41 Rokuban-cho, Atsuta-ku, Nagoya 456, Japan (Received April 28,1995) (Revised June 2 1,1995) Introduction
Ceramic whisker or particulate reinforced aluminium alloy composites are attractive for application to automobile engineering components, aerospace structures, semi-conductor packaging and etc. since these composites exhibit excellent mechanical, physical and thermal properties and also superplasticity produced at high strain rate such as 0.1 - 10 S“ [l-l 0, 121 is expected to allow near-net shape forming of parts or structure components made of such materilas. An AIN particulate reinforced altuninium alloy composite exhibits a high elastic moduhts and a high thermal conductivity[l 11. Moreover, its thermal expansion is similar to silicon so that this composite is expected to apply to semi-conductor packaging in the aerospace structure. In addition, it was also found that the composite could produce superplasticity at high strain rates[ 121. But the super-plastic characteristics of the aluminium alloy composites has not yet been clear entirely. Superplastic det?ormationmechanisms of AlN particulate reinforced album alloy composites include grain boundary sliding[8], interfacial sliding with the presence of a liquid phase[8,9] and dynamic recrystalization, because a lot of experimental results demonstrated that strain rate sensitivity(m value) of superplasticmeti.manixcomposites[3-61 wasintherangeof0.3-0.5, whichshowsthatfinegrainboundary sliding is a predominant deformation mechanism. As AlN particulate reinforced alttminium alloy composite has a lot of interfaces, the superplasticdeformation mechanism should be di&rent from that of a conventional superplastic aluminium alloy. Therefore, it is important to make clear, experimentally, how grain boundary sliding could control HSRS, or ifinterfacial sliding at a liquid phase could occur during HSRS and if dynamic recrystalization c.an contribute to HSRS. The purpose of this study is to develop a thermomechanical processing route to produce a tine microstructure and to huther produce HSRS in a lN90 pure aluminium and in a AlN particulate reinforced lN90 pure aluminum composite. In addition, the superplastic characteristics of the composite and the pure alummium will also be discussed
1333
HIGH STRAINSUPERPLASTICITY
1334
Vol. 33, No. 8
TABLE 1
ChemicalCompositionsof AlN ParticlesUsed as ReinforcementMaterial material
AIN
Fe
Si
cu
hQ
Ni
Cr
0
N
C
PPm 69
PPm 102
Ppm 5
PPm 14
Ppm 5
ppm 6
wt% 1.29
wt% 32.9
wt% 0.03
AlN particle (average particle size of 1.78~) was used as reinforcement material. Table 1 and 2 indicate chemical compositions of AlN particle and lN90 pure ahtminium(Japanese standard), respectively. AhWIN Al composite was sir&red under pressure of 200MPa at 773K for 20 minutes and extruded with the extrusion ratio of 44 at 773K. Thermomechanicalprocessing, includinghot extrusion and further hot rolling, was used to produce HSRS composite. Hot rolling was carried out at 913 or 923 K. Thickness reduction per each pass was less than 0.1 and the reheating time between each rolling passes was about 5 minutes. The final thickness of the hot-rolled composite was about 0.35-0.75mm. Tensile specimens with a 4 mm gage width and a 5.5 mm gage length were made. Test orientation was coincident with extruded and hot rolled directions. Specimens were pulled at 9 13 K and at strain rates ranging from 1 x 1v2 to 2 se1in constant crosshead speed. Flow stresses were determined by maximum flow stress in true stress-true strain curves. Microstructure and fracture surface of the samples were examined by TEM and SFM. Results and Discussion
Figure 1 (a) and (b) show the TEM microstructures (gram size) of (a) pure aluminium lN90 and (b) AlN/lN90 aluminiumcomposite hot-rolled and extruded. The gram sizes of pure ahnninium and AWIN Al composite are about 2pm. Therefore, the lN90 Al and the composite is expected to produce superplasticity at high strain rate. AlN particles were dispersed homogeneously in the hot-rolled A&J/l N90 Al composite as the particle size distribution of AlN is very narrow. Flow stress (a)and true strain rate g) in a superplastic material are related via the equation o = Ki m where K is a constant, and m is the strain rate sensitivity value. The m value of a super-plastic material is normally greater than 0.3 because a high m value is expected to suppress neck formation and leads to high tensile elongation. The relationships between the flow stress and the strain rate of the hot-rolled lN90 pure aluminum and AlN/lN90 Al composite as compared with that of AlN/6061 Al composite are shown in Fig. 2. Testing temperatum of lN90 pure Al and AlN/lN90 Al composite is 913K which is just below melting temperature of pure aluminium (93313). TABLE 2 Chemical material
IN90
Compositionsof lN90 Pure Aluminium
Fe
Cu
Si
Zn
Mn
Mg
Ti
ppm 43
ppm 6
ppm 41
ppm 17
ppm 5
ppm 3
ppm 2
Cr -
Ni
Al
ppm 3
wt% 99.99
1335
HIGH STRAIN SUPERPIASTICITY
Vol. 33, No. 8
Figure 1. TEM microstructures of (a) lN90 pure ahuninium and (b) the AWlN90
Al omposite hot-rolled and exbuded,
The strain rate sensitivity value, m, of the AlNIlN90 Al composite hot-rolled at 923K &et- extrusion is about 0.3 in strain rate range from 0.05 s“ upto 0.2, although the m value of the AlN/6061 Al composite exhibits about 0.49. But the m value of lN90 pure ahrminium indicates also about 0.49 in the relatively low strain rate range from 0.005 up to 0.025 5-l.Therefore, it is shown that the lN90 pure ahuninium alone and the AlN/l N90 AI composite processed by hot-rolling after extrusion could produce the HSRS. Tensile elongations of the AlNIl N90, the AlN/606 1 Al composites [ 111,and 1N90 pure aluminium as a function of strain rate are shown in Fig. 3. The maximum tensile elongation of about 200% in the AlN/lN90 Al composite was obtained at strain rate range from about 0.1 s-r to 0.3 s“ and at 913K (below melting temperature), ahhough the IN90 pure aluminium alone shows the total elongation more than 200% at the relatively lower strain rate of about 0.015 6’ and at the same temperature. What is interesting in the AM/IN90 Al composite is that the optimum strain rate at which maximum total elongation is obtained is almost the same as that of the AM/606 1 Al composite. But, the AlN/606 1 Al composite still maintains the total elongation of 300% at the very high strain rate of 1.0 s-‘. On the other hand, in strain rates higher than 0.3 s-r, the elongation value of the AWlN90 Al composite begins to decrease as the m value becomes slightly low [ 131,
100
10
.i)ol
.Ol
.l Strain
1
10
rate (l/see)
Figure 2. Relationships between flow stress and strain rate ofthe AlN/IN90 Al composite and the lN90 pure aluminum extrudedand hot-rolled
HIGH STRAJN SUPERPLASTlCITY
1336
Vol. 33, No. 8
lN90 alone, AlNIlN90 land MN16061....................................! I
100 -Rolling ____-
teFP=-
0 l
A
;923K(AINllN90) ‘--;823K(lN90 alone) ;818K(AlN/6061) I
lo’ * ’ ***‘* .r101 .Ol
.1
1
CL.
10
Strain rate (llsec) Figure 3. Relationships between total elongation and strain rate of the lN90 pure ahminium, composites hot-rolled and extruded.
the AWlN90
and AM606 1 Al alloy
which indicates that void initiates in higher strain rate than 1.O 6’. A total elongation over 100% can be obtained in a wide strain rate range from 0.0 15 s-’ up to 0.9 s-’ in the AlN/lN90 Al composite. ‘EM observation in Fig. 1 shows that the grain sizes of the lN90 pure aluminium and the AlN/lN90 Al composite have almost the same size of 2pm, although optimum strain rate of the HSRS for the lN90 aluminium alone becomes lower at ten times than that of the AlN/l N90 Al composite. The results indicate
Energy
(keYI
Figure 4. EDS analysis at the interface and in the matrix for AlN2/1N90 Al composite hot-rolled a&r extrwim
Vol. 33, No. 8
HIGH STRAINSUPERPLASTIClTY
1337
Figure 5. Fracture surfaces ofthe AlN/lN90 aluminium alloy composite hot-rolled ad extruded. (a) is pulled at 0.049s”. The total elongstions of (a) is 1159%snd that of @) is 246”/4 respectively.
that hne grain size is a predominant factor to increase the optimum strain rate at which the HSRS occurs. The necessary condition to produce super-plasticityin conventional supetplastic al~umiums includes a fine and equaxial gram with a high angle gram boundary. Therefore, it is thought that the di&rence of the optimum strain rate in the HSRS between lN90 pure ahtminium alone and the AlN/lN90 Al composite might be related with a structure of the grain boundary such as high angle gram boundary. Magnesium and Copper segregations in the SiCJ6061, AlN/606 1, Si,N,w/2 124 and Si,N,w/7064 Al composites have been demonshand by L!Esperance et al. [9] and Imai et al. [lo] and it has been thought that an interfacial slidingwith the presence ofliquid phase is associated with solute segregation and eutectic phase formation at or near an interface between a matrix and a reinforcement in ahtminium ahoy composites reinforced by ceramic whiskers or particulates. But, EDS analysis of the AlN/lN90 Al composite in Fig.4 detects only ahmtinium and carbon at the interface between AlN particle and lN90 pure ahuninium matrix. The above results support the fact that primarily deformation mechanism of the HSRS of the 1N90 aluminium alone and the AlN/lN90 Al composite is grain boundary sliding, but the presence of a thin liquid phase probably might enhance the HSRS of AlN/6061 Al composite, The fracture surface of the AlN/lN90 Al composite contains a partially liquid phase and filament as shown in Fig. 5. The strain rates and the total elongations of the:AWlN90 composites are (a) 0.049 s “and 159%, and (b) 0.27 S’ and 246%, respectively. Conclusions
The super-plastic characteristics of lN90 pure aluminium alone and AlN/lN90 pure aluminum composite, fabricated by P/M method and hot-rolled after extrusion, were investigated. The following results were obtained:
(1) The strain rate sensitivity (m value) of the AlNIl N90 aluminum composites is about 0.3 and the total elongation of the composite become 1OO-200% in strain rate range from .02 up to 1.O s-’ and at 913K.
(2) The lN90 pure aluminumalone indicates the m value of about 0.45 and the total elongation of 200 % in strain rate range fi-om 0.002 8’ and at 913K. (3) Grain sizes of the IN90 pure aluminium alone and the AWlN90
Al composite aftersuper plastic defonnation are about 2pm. (4) EDS analys’isat the interface and on the matrix of the AUWlN90 pure aluminium composite indicates only ahuninium and carbon.
1338
HIGH STRAIN SUPERF’LASTICITY
Vol. 33, No. 8
(5) These results indicate that predominant deformation mechanism of the 1N90 purealuminium alone and
the AlNllN90 Al composite is a grain boundary sliding. References 1. 2. 3. 4. 5. 6. 7. 8 9. 10. 11. 12. 13.
14. 15.
T.G. Nieb, C.A. Henshall and J. Wadsworth, Scripta Metalhqica, 18-12(1984) 1405-1408 M.W. Mahoney and AK Ghcsh, Metall. Tram, 18A(1987) 653661 T. Imai, M.Mabuchi, Y. Tozawa and M. Yamada, JMatcrials Science letters, 9 (1990) 255-257 M. Mabuchi, T. I&, K. Kubo, H. Hi&i, Y. Okada and T. Tanimum, Materials Le.&x, 10 (1991) 339-342 M. Mabuchi, K H&&i, Y. Okada, S. Tanimum, T.ImaiaudK.Kubo,Scripta Meklhqica et Makrialia, 25 (1991)2517-2522 T. Imai. M. Mabuchi and T. Tozawa, Supcrpktkity in advanced materials edited by S.Hori,M.Tokizane and N.Fwushin$A Publication of JSRS,1991)373-378 T. Tsuzuku and A Takah&i, Proc. of 1st Japan Inkmational SAMPE Symposium (Nov.28~Deal, 1989)243. T.G. Nieh and J. Wadsworth, Supcrplasticity in Advanced Materiak edited by S. Hori, M. Tokizanc and N. Futushiro (A Publication of JSRS, 1991), 339-348 G. L’Ekpexance, T. hnai awl B.Hong. ibid, 379-384 T. hnai, G.L ‘L’Espgdnce, B. Hong. M. Mabuchi, and Y. Tozawa, Advances in Powder Metalhqy & Particulate Materials-1992 compiled by J.M. Caus and RM. German, 9 (1992)181-194 T. Imai, G.L ‘LEsperance & B.D. Hong, Scripta Mctallst Mater., (1994) in press S. Kem&a&$ FabrktiionofPattiadate Rcinked M&l Compositea, Edited by J. Masounave t F.G. Hamcl, (1990, Published by ASM Intcmational) 87-100. K H&a&i, T. Okada, T. Mukai, S. Tanimura, T.G. Nieh, and J. Wadsworth, inmlntl. Meeting on AdvancedMaterialsVoZ 7(IUMRSIW93, Sjmp. E, SuperpkWici~), edited by M. Doyama, S. Somiya, and RP.H. Chaq Pergamon Press, Nctherhmd (1993). inpress T.G. Nieh, J. Wadsworth, and T. hnai, Scripta Metall. Mater., 26 (1992) 55 l-556. M. Mabuchi, K H&a&i, Y. Okada, S. Tanimura, T. Imai, and K Kubo, Scripta Metall. Mater. 25 (1991) 2003-2006.