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Pharmacological evidence for a correlation between hippocampal CA1 cell damage and hyperlocomotion following global cerebral ischemia in gerbils
Applied Mechanics and Materials Vols. 66-68 (2011) pp 2005-2009 © (2011) Trans Tech Publications, Switzerland doi:10.4028/www.scientific.net/AMM.66-68.2005
Online: 2011-07-04
Two-Phase Matrix of Ni3Al and γ- Ni Coatings Prepared by Laser Cladding CHENG Guangping 1, 2,a, HE Yizhu 1,2,b 1
School of Materials Science and Engineering，Anhui University of Technology, Maanshan 243002, Anhui, China 2
Anhui Key Lab. of Metal Material and Processing, Maanshan 243002, Anhui,China a
[email protected], [email protected]
Keywords: Laser cladding, Intermetallic, Coating, Ni3Al
Abstract. As a solid solution matrix alloy, nickel-based alloys have the shortcomings that the strength will decrease with increasing temperature. The significance of this experiment is forming the two-phase matrix, in which γ- Ni solid solution are replaced partly by Ni3Al with potential performance at high temperature. In this paper, no visible cracks and pores Ni3Al/γ- Ni composite matrix coatings were prepared on mild steel substrate by laser cladding with mixed powders of two common thermal spying powders of Ni60AAA alloy and Ni-coated Al. The microstructure and phase constitution of the coating were studied through SEM, EDX and x-Ray diffraction analysis technique. The results show the composite coating consists of γ- Ni, Ni3Al, Cr23C6 and CrB, both the main matrix γ- Ni solid solution and the second matrix phase of Ni3Al being free uniformity dendrite and containing some alloying elements such as Fe, Cr, Si, etc,with the dendrites surrounded continuously by the eutectic. It may be possible for improving high-temperature performance. Introduction Nickel-based alloys with the γ solid solution being matrix phase, have good toughness, excellent high temperature oxidation and corrosion resistance, and become the most used laser cladding material [1-3]. Despite the high temperature performance of nickel-based alloys is superior to iron-based alloy, but as a solid solution matrix alloy, nickel-based alloys have the same shortcomings that the strength will decrease with increasing temperature. As a new high temperature structural material, Ni3Al intermetallic compound have the high temperature oxidation resistance superior to nickel-based alloys. Despite the Young's modulus of Ni3Al at room temperature are similar with pure nickel, but with increasing temperature the decline slope of Young's modulus is about half of pure nickel [4]. So compared with γ-Ni solid solution, Ni3Al may have potential advantage of high temperature strength. When the γ-Ni solid solution phase in nickel-based alloys are replaced partly with Ni3Al, for example formation of Ni3Al and γ-Ni composite matrix, it may be possible for improving high-temperature performance, reducing amount of nickel and saving precious metals. Nickel-coated-aluminum powders are commonly used as thermal spray bottoming alloy in pre-spray process to form Ni-Al intermetallic compounds [5]. In this paper, low-carbon nickel-based alloys and nickel-coated-aluminum powders are used as raw material to synthesis and prepare nickel-based solid solution and Ni3Al intermetallic composite laser claddings, and the coatings microstructure and process characteristics are studied.
All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of Trans Tech Publications, www.ttp.net. (ID: 131.215.225.9, California Institute of Technology, Pasadena, USA-12/07/15,16:16:41)
2006
Mechanical, Materials and Manufacturing Engineering
Expermental methods The mild steel is used as the substrate. Ni60AAA (Nickel-base alloy) and Ni-coated-Al powders are mixed as the coating material. The weight content of Ni60AAA and Ni-coated Al powder(mass fraction) are 60% and 40% respectively, with the mass component of Ni60AAA is C<0.2%, 3%B, 4%Si, 15%Cr, and the mass or atom components of Al in Ni-coated-Al are 17~22% or 31~38%. Before laser cladding, the drying and mixing powders are putted on the substrate surface. The pre-heated powders and substrate are carried cladding in single track with different powers of 1.8~2.2kW by a 5 kW continuous wave CO2 laser with protective argon gas. The multiple tracks cladding power is determined as 2kW, according to the single tracks condition of melting pool and the quality of the coatings. The experimental parameters are as follows: laser beam diameter is 6mm; scanning speed is 200mm/min; the ratio of overlap is 50%. After cladding, the samples are treated by annealing at 300℃~400℃ for several hours. The coats microstructures are observed by OM, SEM, the micro-area composition of phase are analyzed by EDS, and the coats phase constitution are analyzed by XRD. Results and discussion The macrostructure of coating interface Fig.1 shows the macrostructure of substrate/coating interface with the substrate etched by 4% nitric acid solution of alcohol and the coating etched by corrosion agents of hydrochloric acid: nitric acid = 3:1. It is obviously that there is a complete and continuous white band in interface of the upper coating and the bottom substrate which indicates the complete metallurgical combination between the coat and substrate. Although corrosion coating microstructure observation shows that there is a certain inhomogeneity degree of coating composition and microstructure, overall, the coatings have a good quality that no visible cracks and pores or inclusions have been observed. The experiments show the mixed powders of Ni60AAA alloy and Ni-coated-Al have good cladding performance, which are related with the Ni60AAA powders chemical composition and properties. Ni60AAA powders are self-fluxing alloy and contain alloying elements Cr, B, Si, etc, which have some roles such as reducing the melting point of the base, forming a protective slag, improving liquidity, being deoxidation, and so on. So the mixed experimental powders have low melting temperature and consequently need lower laser cladding power.
coating
substrate
200µm m
Fig. 1 The macrostructure of coating interface
Applied Mechanics and Materials Vols. 66-68
2007
The microstructure of coating Fig.2 shows the microstructure of the composite coatings. It shows the coating mainly consists of three kinds of microstructure, with the matrix including two dendritic phases shown as the grain A and grain B in Fig.2, and the lamellar eutectic distributing around the dendrites shown as the area C in Fig.2. a
b
B
A C
25μ μm
Fig.2 The OM micrograph (a) and SEM image (b) of composite coatings Tab.1 EDS analysis results(atom content) of the matrix dendrite phase A, phase B and eutectics C Element(at%) dendritic phase A eutectic C dendritic phase B Ni Al Fe Cr Si
55.2 10.2 23.3 6.6 4.7
57.8 22.5 13.3 2.8 3.6
23.1 3.2 27.5 44.2 2.0
Tab.1 shows the spectrum analysis results of the two dendritic phases and the eutectics microstructure. The atom ratios of Ni:Al:Fe:Cr:Si in dendritic phase A and B are respectively 55:10:23:7:5 and 58:22:13:3:4. Both in phase A and phase B, the most element is Ni (atom content is 55%-58%) and the two amounts are similar in phase A and B, then a few amount of Cr, Si which are also similar in phase A and B. The most different between phase A and B is the contents of Al and Fe, the former have less Al (atom content is 10%) but more Fe (atom content is 23%), and the latter have more Al (atom content is 22%) and less Fe (atom content is 13%). Although the material powders do not contain Fe, considerable number of Fe are solid solution both in phase A and B which come from the steel base, for the Fe being large solid solubility in nickel and nickel-aluminum compounds. So phase A and phase B should be solid solution of nickel or intermetallics of Ni-Al or Ni-Al (Fe). Eutectic C contain mainly Cr, so the eutectics should contain a large number of chromium boride or carbide. The phase constitution To investigate the phase constitution, XRD analysis to the cladding is carried out. Combined with the coatings energy spectrum analysis to phase A, phase B and eutectic microstructure C, showing as tab.1 on preceding paragraph, the phase constitution can be obtained. Fig.3 shows the XRD pattern of composite coating and the result of phase constitution. It shows that the layer mainly consists of γ-Ni, Ni3Al, Cr23C6 and CrB.
2008
Mechanical, Materials and Manufacturing Engineering
Combined with the X-ray diffraction phase analysis and spectrum analysis, phase A should be γ-Ni, phase B should be Ni3Al, and the eutectics C should consist of γ-Ni, Cr23C6, and CrB, etc. In phase B, the aluminum atom content is lower than the theoretical value of Ni3Al, the lack aluminum are instead by subrogation iron and other elements [6]. Usually a variety of alloy elements can integrate in subrogation into Ni3Al, for example, Cr only occupy and replace the position of Ni, Si only occupy the position of Al, while Fe can occupy and replace both the position of Ni and Al. Taking into account the role of each element of subrogation, the Al atomic percentage in free dendrite B (containing Si, Fe) is ranging between 25% -38%, which is consistent with the scope of Al atomic percentage in Ni3Al.
Fig.3 XRD patterns of composite coating The formation causes of the composite coating can be explained as follows: the melting points of the two cladding materials(Ni60AAA and nickel-coated aluminum) have a certain gap, despite the diffusion process occurs after cladding, the laser ultra-fast heating and ultra-fast cooling often results in partial uneven melting and non-equilibrium solidification. The liquid near nickel-coated aluminum contain much more Al and react to form dendritic Ni3Al, while the remaining liquid meet γ -Ni solid solution composition, the solidification process in the subsequent transition through the crystallization of the isomorphous γ-Ni solid solution dendrites as the temperature further reduced the remaining eutectic liquid phase transition, and form a mesh around the two dendrites eutectic. In this study, Ni3Al/γ- Ni composite matrix coatings are prepared by laser cladding with mixed powder of two common thermal spying powders of nickel-base alloy and Ni-coated Al. The significance of this experiment are forming the two-phase matrix, in which γ- Ni solid solution are replaced partly by Ni3Al with potential performance at high temperature, so it may be possible for the two-phase matrix composite coatings improving the strength and other performance at high temperature potentially. Conclusions Ni3Al/γ- Ni composite coatings are prepared on mild steel substrate by Laser cladding with mixed powder of nickel-base alloy and Ni-coated Al. The composite coating consists of three kinds of microstructure morphology, the main matrix dendrite phase is γ- Ni solid solution and the free uniformity dendrite phase is Ni3Al, the eutectic is distribution network on the interface of the two dendrites. The elements of Fe,Cr and Si are solid soluted into both phases of γ- Ni and Ni3Al.
Applied Mechanics and Materials Vols. 66-68
2009
Acknowledgements The authors gratefully acknowledge financial support from the Natural Science research projects funded by Technology Department of Anhui Province, China (Project No. 08080703020) . References [1] K.S. Yun, J.H. Lee, C.W. Won. Materials Research Bulletin, Vol.35(2005), p.1709. [2] K. Spencer, M. X. Zhang. Surface & Coatings Technology, Vol.38 (2009), p.1. [3] J.T.GUO, in: Ordered intermetallic compound NiAl alloy, edtied by Science Press, Beijin (2003), in Chinese. [4] G.L.CHEN, J.P.LIN, in: Fundamentals of physics metallurgy on intermetallic compounds for structural application , edtied by Metallurgy Industry Press, Beijin (1999) , in Chinese. [5] D.K.NIE, Y.X.LI. Applied Laser, Vol.22 (2002), p.93. [6] G.P.CHENG, Y.Z.HE. Journal of Materials Engineering Vol.45(03) (2010), p.29, in Chinese.
Mechanical, Materials and Manufacturing Engineering 10.4028/www.scientific.net/AMM.66-68
Two-Phase Matrix of Ni3Al and γ- Ni Coatings Prepared by Laser Cladding 10.4028/www.scientific.net/AMM.66-68.2005
Online: 2011-07-04
Two-Phase Matrix of Ni3Al and γ- Ni Coatings Prepared by Laser Cladding CHENG Guangping 1, 2,a, HE Yizhu 1,2,b 1
School of Materials Science and Engineering，Anhui University of Technology, Maanshan 243002, Anhui, China 2
Anhui Key Lab. of Metal Material and Processing, Maanshan 243002, Anhui,China a
[email protected], [email protected]
Keywords: Laser cladding, Intermetallic, Coating, Ni3Al
Abstract. As a solid solution matrix alloy, nickel-based alloys have the shortcomings that the strength will decrease with increasing temperature. The significance of this experiment is forming the two-phase matrix, in which γ- Ni solid solution are replaced partly by Ni3Al with potential performance at high temperature. In this paper, no visible cracks and pores Ni3Al/γ- Ni composite matrix coatings were prepared on mild steel substrate by laser cladding with mixed powders of two common thermal spying powders of Ni60AAA alloy and Ni-coated Al. The microstructure and phase constitution of the coating were studied through SEM, EDX and x-Ray diffraction analysis technique. The results show the composite coating consists of γ- Ni, Ni3Al, Cr23C6 and CrB, both the main matrix γ- Ni solid solution and the second matrix phase of Ni3Al being free uniformity dendrite and containing some alloying elements such as Fe, Cr, Si, etc,with the dendrites surrounded continuously by the eutectic. It may be possible for improving high-temperature performance. Introduction Nickel-based alloys with the γ solid solution being matrix phase, have good toughness, excellent high temperature oxidation and corrosion resistance, and become the most used laser cladding material [1-3]. Despite the high temperature performance of nickel-based alloys is superior to iron-based alloy, but as a solid solution matrix alloy, nickel-based alloys have the same shortcomings that the strength will decrease with increasing temperature. As a new high temperature structural material, Ni3Al intermetallic compound have the high temperature oxidation resistance superior to nickel-based alloys. Despite the Young's modulus of Ni3Al at room temperature are similar with pure nickel, but with increasing temperature the decline slope of Young's modulus is about half of pure nickel [4]. So compared with γ-Ni solid solution, Ni3Al may have potential advantage of high temperature strength. When the γ-Ni solid solution phase in nickel-based alloys are replaced partly with Ni3Al, for example formation of Ni3Al and γ-Ni composite matrix, it may be possible for improving high-temperature performance, reducing amount of nickel and saving precious metals. Nickel-coated-aluminum powders are commonly used as thermal spray bottoming alloy in pre-spray process to form Ni-Al intermetallic compounds [5]. In this paper, low-carbon nickel-based alloys and nickel-coated-aluminum powders are used as raw material to synthesis and prepare nickel-based solid solution and Ni3Al intermetallic composite laser claddings, and the coatings microstructure and process characteristics are studied.
All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of Trans Tech Publications, www.ttp.net. (ID: 131.215.225.9, California Institute of Technology, Pasadena, USA-12/07/15,16:16:41)
2006
Mechanical, Materials and Manufacturing Engineering
Expermental methods The mild steel is used as the substrate. Ni60AAA (Nickel-base alloy) and Ni-coated-Al powders are mixed as the coating material. The weight content of Ni60AAA and Ni-coated Al powder(mass fraction) are 60% and 40% respectively, with the mass component of Ni60AAA is C<0.2%, 3%B, 4%Si, 15%Cr, and the mass or atom components of Al in Ni-coated-Al are 17~22% or 31~38%. Before laser cladding, the drying and mixing powders are putted on the substrate surface. The pre-heated powders and substrate are carried cladding in single track with different powers of 1.8~2.2kW by a 5 kW continuous wave CO2 laser with protective argon gas. The multiple tracks cladding power is determined as 2kW, according to the single tracks condition of melting pool and the quality of the coatings. The experimental parameters are as follows: laser beam diameter is 6mm; scanning speed is 200mm/min; the ratio of overlap is 50%. After cladding, the samples are treated by annealing at 300℃~400℃ for several hours. The coats microstructures are observed by OM, SEM, the micro-area composition of phase are analyzed by EDS, and the coats phase constitution are analyzed by XRD. Results and discussion The macrostructure of coating interface Fig.1 shows the macrostructure of substrate/coating interface with the substrate etched by 4% nitric acid solution of alcohol and the coating etched by corrosion agents of hydrochloric acid: nitric acid = 3:1. It is obviously that there is a complete and continuous white band in interface of the upper coating and the bottom substrate which indicates the complete metallurgical combination between the coat and substrate. Although corrosion coating microstructure observation shows that there is a certain inhomogeneity degree of coating composition and microstructure, overall, the coatings have a good quality that no visible cracks and pores or inclusions have been observed. The experiments show the mixed powders of Ni60AAA alloy and Ni-coated-Al have good cladding performance, which are related with the Ni60AAA powders chemical composition and properties. Ni60AAA powders are self-fluxing alloy and contain alloying elements Cr, B, Si, etc, which have some roles such as reducing the melting point of the base, forming a protective slag, improving liquidity, being deoxidation, and so on. So the mixed experimental powders have low melting temperature and consequently need lower laser cladding power.
coating
substrate
200µm m
Fig. 1 The macrostructure of coating interface
Applied Mechanics and Materials Vols. 66-68
2007
The microstructure of coating Fig.2 shows the microstructure of the composite coatings. It shows the coating mainly consists of three kinds of microstructure, with the matrix including two dendritic phases shown as the grain A and grain B in Fig.2, and the lamellar eutectic distributing around the dendrites shown as the area C in Fig.2. a
b
B
A C
25μ μm
Fig.2 The OM micrograph (a) and SEM image (b) of composite coatings Tab.1 EDS analysis results(atom content) of the matrix dendrite phase A, phase B and eutectics C Element(at%) dendritic phase A eutectic C dendritic phase B Ni Al Fe Cr Si
55.2 10.2 23.3 6.6 4.7
57.8 22.5 13.3 2.8 3.6
23.1 3.2 27.5 44.2 2.0
Tab.1 shows the spectrum analysis results of the two dendritic phases and the eutectics microstructure. The atom ratios of Ni:Al:Fe:Cr:Si in dendritic phase A and B are respectively 55:10:23:7:5 and 58:22:13:3:4. Both in phase A and phase B, the most element is Ni (atom content is 55%-58%) and the two amounts are similar in phase A and B, then a few amount of Cr, Si which are also similar in phase A and B. The most different between phase A and B is the contents of Al and Fe, the former have less Al (atom content is 10%) but more Fe (atom content is 23%), and the latter have more Al (atom content is 22%) and less Fe (atom content is 13%). Although the material powders do not contain Fe, considerable number of Fe are solid solution both in phase A and B which come from the steel base, for the Fe being large solid solubility in nickel and nickel-aluminum compounds. So phase A and phase B should be solid solution of nickel or intermetallics of Ni-Al or Ni-Al (Fe). Eutectic C contain mainly Cr, so the eutectics should contain a large number of chromium boride or carbide. The phase constitution To investigate the phase constitution, XRD analysis to the cladding is carried out. Combined with the coatings energy spectrum analysis to phase A, phase B and eutectic microstructure C, showing as tab.1 on preceding paragraph, the phase constitution can be obtained. Fig.3 shows the XRD pattern of composite coating and the result of phase constitution. It shows that the layer mainly consists of γ-Ni, Ni3Al, Cr23C6 and CrB.
2008
Mechanical, Materials and Manufacturing Engineering
Combined with the X-ray diffraction phase analysis and spectrum analysis, phase A should be γ-Ni, phase B should be Ni3Al, and the eutectics C should consist of γ-Ni, Cr23C6, and CrB, etc. In phase B, the aluminum atom content is lower than the theoretical value of Ni3Al, the lack aluminum are instead by subrogation iron and other elements [6]. Usually a variety of alloy elements can integrate in subrogation into Ni3Al, for example, Cr only occupy and replace the position of Ni, Si only occupy the position of Al, while Fe can occupy and replace both the position of Ni and Al. Taking into account the role of each element of subrogation, the Al atomic percentage in free dendrite B (containing Si, Fe) is ranging between 25% -38%, which is consistent with the scope of Al atomic percentage in Ni3Al.
Fig.3 XRD patterns of composite coating The formation causes of the composite coating can be explained as follows: the melting points of the two cladding materials(Ni60AAA and nickel-coated aluminum) have a certain gap, despite the diffusion process occurs after cladding, the laser ultra-fast heating and ultra-fast cooling often results in partial uneven melting and non-equilibrium solidification. The liquid near nickel-coated aluminum contain much more Al and react to form dendritic Ni3Al, while the remaining liquid meet γ -Ni solid solution composition, the solidification process in the subsequent transition through the crystallization of the isomorphous γ-Ni solid solution dendrites as the temperature further reduced the remaining eutectic liquid phase transition, and form a mesh around the two dendrites eutectic. In this study, Ni3Al/γ- Ni composite matrix coatings are prepared by laser cladding with mixed powder of two common thermal spying powders of nickel-base alloy and Ni-coated Al. The significance of this experiment are forming the two-phase matrix, in which γ- Ni solid solution are replaced partly by Ni3Al with potential performance at high temperature, so it may be possible for the two-phase matrix composite coatings improving the strength and other performance at high temperature potentially. Conclusions Ni3Al/γ- Ni composite coatings are prepared on mild steel substrate by Laser cladding with mixed powder of nickel-base alloy and Ni-coated Al. The composite coating consists of three kinds of microstructure morphology, the main matrix dendrite phase is γ- Ni solid solution and the free uniformity dendrite phase is Ni3Al, the eutectic is distribution network on the interface of the two dendrites. The elements of Fe,Cr and Si are solid soluted into both phases of γ- Ni and Ni3Al.
Applied Mechanics and Materials Vols. 66-68
2009
Acknowledgements The authors gratefully acknowledge financial support from the Natural Science research projects funded by Technology Department of Anhui Province, China (Project No. 08080703020) . References [1] K.S. Yun, J.H. Lee, C.W. Won. Materials Research Bulletin, Vol.35(2005), p.1709. [2] K. Spencer, M. X. Zhang. Surface & Coatings Technology, Vol.38 (2009), p.1. [3] J.T.GUO, in: Ordered intermetallic compound NiAl alloy, edtied by Science Press, Beijin (2003), in Chinese. [4] G.L.CHEN, J.P.LIN, in: Fundamentals of physics metallurgy on intermetallic compounds for structural application , edtied by Metallurgy Industry Press, Beijin (1999) , in Chinese. [5] D.K.NIE, Y.X.LI. Applied Laser, Vol.22 (2002), p.93. [6] G.P.CHENG, Y.Z.HE. Journal of Materials Engineering Vol.45(03) (2010), p.29, in Chinese.
Mechanical, Materials and Manufacturing Engineering 10.4028/www.scientific.net/AMM.66-68
Two-Phase Matrix of Ni3Al and γ- Ni Coatings Prepared by Laser Cladding 10.4028/www.scientific.net/AMM.66-68.2005