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Correlations between hardness and tensile strength of cracked aluminium plates repaired with composite patches
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ScienceDirect Materials Today: Proceedings 21 (2020) 1335–1339
www.materialstoday.com/proceedings
ICRACM-2019
Correlations between hardness and tensile strength of cracked aluminium plates repaired with composite patches Bishnupriya Dehuria, Shashwati Soumya Pradhanb,* a a
Civil Engineering Department, CAPGS, Biju Patnaik University of Technology, Rourkela, Odisha, 769015, India Civil Engineering Department, CAPGS, Biju Patnaik University of Technology, Rourkela, Odisha, 769015, India
Abstract The correlations between Rockwell hardness and tensile strength of cracked aluminium plates repaired with composite patches were studied. Composite patch on tensile strength of woven fabric, glass/epoxy composite laminates and the aluminium plates having 3 mm thickness of the three different crack length of 5 mm, 10 mm and 15 mm. Tensile tests of composite patch are performed on [0/90], in case of two lay-ups were used, viz. 4-ply and 6-ply. Under the hardness and tensile loading conditions, there is an important role of the reinforcement fraction and matrix strength in effecting the behavior of composite. The tensile test and hardness test are compared regarding the different loading modes. Result in a significant overestimation of the tensile strength of the hardness test, especially when the matrix strength is relatively low. The tensile strength of two materials is reduced while the difference in the hardness increases. © 2019 Elsevier Ltd. All rights reserved. Selection and peer-review under responsibility of SIXTH INTERNATIONAL CONFERENCE ON RECENT ADVANCES IN COMPOSITE MATERIALS, ICRACM-2019. Keywords:Composite; Hardness; Aluminium; Tensile strength
1. Introduction Hardness tests are most commonly utilized as a basic and successful method for the observation of the mechanical strength of metallic materials [1]. The interrelationship between different hardness scales and tensile strength has been arranged for a number of different types of alloy [2]. Composites shows significantly extreme utilization for purposes where quality control may be essential, it is necessary to correlate between hardness and
* Corresponding author. Tel.: +0-943-935-1426. E-mail address:[email protected] 2214-7853© 2019 Elsevier Ltd. All rights reserved. Selection and peer-review under responsibility of SIXTH INTERNATIONAL CONFERENCE ON RECENT ADVANCES IN COMPOSITE MATERIALS, ICRACM-2019.
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tensile strength in similar type of materials. After reinforcement composition the matrix allows is placed, the letter is denoted by the subscript ‘p’ as a particulate reinforcement. The researcher described the linear relationship between the Rockwell shallow-scale hardness and the ultimate tensile strength of the composite. For composites which have large reinforcement particles that might get fracture during the process of deformation. While in tension the fractured particles do not carry any applied load, they do not change accordingly the resistance to local compressive loading in hardness test. Experimental investigation [3] determined Griffiths micro hardness maps of cross-sections of high-pressure die cast test bars of AZ91. The specimens having rectangular cross-sections which are 1, 2 and 3 mm thick, or with a circular cross-section which is 6.4 mm in diameter, the hardness is higher near the edges and also more hardness was found near the corners of the rectangular specimens. While at the centre of the castings the hardness is generally lesser, due to a coarser solidification microstructure and the concentration of porosity. As per the result, it was found that the castings have harder surface the core. Though the hardness is not even on both sides of the casting, the layer is uncertain in hardness and depth. As the thickness of the bars decreases the average hardness increases which is derived by combining the micro hardness maps over the entire cross-section. The researcher [4] simplified the procedure of determination of mechanical properties such as hardness and the Young’s modulus of materials by improved the depth sensing indentation equipment. But sometimes it is difficulties to compute the accurate values of these properties. This is identified with, for example, the tip geometrical imperfections of the diamond pyramidal indenter and the definition of the contact area at the maximum load. Therefore, to determining the hardness and the Young’s modulus for the numerical simulation of ultra micro hardness tests can be a useful tool for better understanding. The software called HAFILM must produce to simulate the ultra micro hardness tests. Different mesh refinements were tested due to the dependence between the estimations of the mechanical properties and the size of the finite element mesh. By another method the yield stress of a metallic material can be formulated using Vickers hardness with taking account of residual stress. It is possible to evaluate the yield stress of bulk metal by a tensile test, but by surface modification methods it is not possible for local yield stress change, for examples, the peening technique which introduces high compressive residual stress at the surface. Therefore, by simple technique the local yield stress is being evaluated and thus the Vickers hardness test was conducted in this paper. The bonding between the residual stress and the Vickers hardness was experimentally examined as the Vickers hardness relies upon both the residual stress and the yield stress. As the test got satisfied for residual stress by above peening technique, so the yield stress of the surface could be evaluated from the Vickers hardness [5]. Researchers [6] were combining two independent studies of 7010 alloy plate and a rectilinear forging analyzed and took the parameters between Vickers hardness, yield stress and tensile strength. From these two studies, the hardness-yield stress data overlapped having general relationship. With the help of contact mechanics models constraint factors were calculated and evaluated. It observed by Shaw and DeSalvo was found to agree with the slope for the hardness–yield stress data. The y-intercept of the hardest–yield stress, relationship was explained by the work hardening, which was occurring during Vickers testing. The equation found to fit the hardness yield stress data for 7010 plate and forgings also provided a very respectable fit for a third independent study. Furthermore, an experimental equation was produced for the hardness–tensile strength relationship. Another research was [7] carried out tensile and impact tests and also hardness measurements on hot forged aluminium metal matrix composites to observe the effect of alloying element and forming process on their mechanical properties. Pure aluminium performs together with its composites for example Al4TiC, Al4Fe3C, Al4Mo2C and Al4WC were prepared utilizing an appropriate die-set get together on a 1MN capacity hydraulic press. Sintering procedure was conducted at 1200°C in an electric muffle heater for a holding time of 1h. Just after the sintering procedure the cylindrical performs were hot distored into a square cross-section bar of size (24 × 24 × 60) mm for preparing of tensile test and impact test samples according to the particular ASTM standards. The test samples of the standard tensile and impact test were fabricated from the forged square bar. The previously mentioned mechanical testing was conducted according to the standard ASTM methods. Furthermore, microstructural experiments on the hot forged square cross-section bar and hardness estimations were found and examined.
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2. Experimental Procedures 2.1. Materials AA 1080 aluminium alloy sheets of 3 mm thickness were used in this experiment. The chemical composition of aluminium alloy is presented in Table 1. Commercially pure aluminium of varying graded of purity is used. These aluminium sheets can easily be formed and joined, but generally have the lowest strength characteristics of all the alloys. Glass fiber is a material, which consists of extremely fine fiber of glass. It is formed when thin strands of silica-based glass are extruded into many fibers. The glass fibers are easy to manufacture and in-expansive. E-glass is used as reinforcement material. Table 2 represents the properties of the patch materials. Table 1. Chemical composition of aluminium alloy. Element
Si
Fe
Cu
Mn
Mg
Zn
Ti
Weight Percentage
0.15
0.15
0.03
0.02
0.02
0.06
0.02
Table 2. Properties of Patch materials Properties
Inference
Tensile Strength
282.8 MPa
Compressive Strength
580.1 MPa
Density
2.58 g/cm3
Thermal Expansion (10-6/k)
8.82
Thermal conductivity
2.24 W/m.k
Softening point
846 0C
Melting Point
1121 0C
Hardness
435.113 Mpa
Bulk modulus
6.236 a
2.2. Details of Specimen
Fig. 1. Composite patch specimen after tensile test According to the ASTM standards, the specimens were prepared by slicing the aluminium sheets to the final dimensions, i.e. (250 x 30) mm and the patch thickness are 1.5 mm, 2.5 mm, 3.5 mm for tensile test. Both the sides of specimens have the gripping length 50 mm each and have gauge length of 150 mm. The specimens were tested at 25°C having crosshead speed 5 mm/min. The cracked plate which was repaired on only one side the surface was made according to the standard procedure for reinforcing a 4 ply and 6 ply composite patches. The hardness is assumed as a property of a material that helps it to resist plastic deformation by penetration. It also helps to resist bending, scratching, abrasion etc. To define the hardness, the standard Rockwell B-scale test was performed which have a 1.58 mm diameter spherical steel intender [8]. The hardness values are measured in the B-scale. The Rockwell B-scale hardness test is generally used to compute the mechanical strength of different kinds of aluminium
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alloy, because this method comprises of some good characteristic features like speed, reproducibility and the comparatively tiny size of the indentation. The minor and major load applied is 10 kg and 100 kg. The depth of indentation beyond the minor load directly determined the hardness value (HRB). 3. Results and Discussion In tension, fractured particles don’t carry any applied load; they don’t change the resistance to local compressive loading in a hardness test, resulting the hardness test can accordingly overestimate the total tensile strength of the composite [9]. Fig. 1 shows the composite patch specimen after the tensile test. The indented region is extensive in comparison to the size and space in between the particle. Therefore, the indentation estimates the total effect of the material and is comparatively unresponsive to confined impacts. A very small amount of cracked particles was found below or far from the indentation. The values obtained from the hardness and ultimate tensile strengths of the materials were included in the hardness and strength data in one plot. In Fig 2. the ultimate tensile strength, function of the hardness (HRB) is shown for the composites. The tensile strength of both the materials is decreased while the difference in the hardness increases. As per the result, it was found that the hardness testing method, which is utilized to measure, the tensile strength may not be useful to particle reinforced metal matrix composites. The converging curves in Fig. 2 shows that if the matrix strength is more, then the impact is decreased.
Fig. 2. Relationship between true ultimate tensile strength and Rockwell B-scale hardness of the composite 4. Conclusions The hardness values and ultimate tensile strength seem to be having same tendency. Two different studies using the crack aluminium alloy repaired with two different plies i.e. 4-ply and 6-ply is quite important and shows a general relationship between hardness and strength. The relationship doesn’t found to be exist between hardness and tensile strength, especially where the matrix strength is comparatively low. There is also significant role of reinforcement fraction affecting the hardness-strength relation. The relationship between tensile strength and Rockwell hardness was also developed. References [1] Chawla, K. kumar., Meyers, M. A. Mechanical behavior of materials. Upper Saddle River: Prentice Hall, (1999), pp. 217. [2] Aray, T., & Harper, S. ASM Handbook, ASM International, Materials Park, OH (1991). [3] Cáceres, C. H., Griffiths, J. R., Pakdel, A. R, Davidson, C. J. Microhardness mapping and the hardness-yield strength relationship in highpressure diecast magnesium alloy AZ91. Materials Science and Engineering: A, 402(1-2), (2005), pp. 258-268. [4] Antunes, J. M., Menezes, L. F, Fernandes, J. V. Three-dimensional numerical simulation of Vickers indentation tests. International Journal of Solids and Structures, 43(3-4), (2006), pp.784-806. [5] Takakuwa, Osamu, Y.Kawaragi, H.Soyama. Estimation of the yield stress of stainless steel from the Vickers hardness taking account of the residual stress. Journal of Surface Engineered Materials and Advanced Technology. (2013), 3(04), pp. 262. [6] Tiryakioğlu, M., J.Robinson, S.Guapuriche, M. A.,Y. Zhao, P. Eason, P. Hardness–strength relationships in the aluminum alloy 7010. Materials Science and Engineering: A,(2015), pp. 196-200.
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[7] Narayan, Sumesh, A.Rajeshkannan. (2017). Hardness, tensile and impact behaviour of hot forged aluminium metal matrix composites. Journal of Materials Research and Technology, 6(3), (2017), pp. 213-219 [8] ASTM Standards, Designation E 18-93. Standard test methods for rockwell hardness and rockwell superficial hardness of metallic materials, 1993. [9] Shen, Y. L., E.Fishencord,,N.Chawla.. Correlating macrohardness and tensile behavior in discontinuously reinforced metal matrix composites. Scriptamaterialia, 42(5), (2000), 427-432. [10] Mochida, M.Taya, D.Lloyd. Fracture of particles in a particle/metal matrix composite under plastic straining and its effect on the Young’s modulus of the composite. Materials Transactions, JIM, 32(10), (1991), pp. 931-942. [11] Krajewski, P. E., J. Allison, J. Jones. The influence of matrix microstructure and particle reinforcement on the creep behavior of 2219 aluminum. Metallurgical and Materials Transactions A 24, no. 12 (1993): 2731. [12] Finot, M., Y. Shen, A. Needleman, S.Suresh. Micromechanical modeling of reinforcement fracture in particle-reinforced metal-matrix composites. Metallurgical and Materials Transactions A 25, no. 11 (1994): 2403-2420. [13] Shen, Y. L, M. Finot, A.Needleman, S. Suresh. Effective elastic response of two-phase composites. Act a metallurgic aetmaterialia, 42(1), (1994) 77-97. [14] Gupta, M. Effect of precipitation on the bulk hardness and the ultimate tensile strength of a 6061/SiC composite. High Temperature Materials and Processes, 17 (4), (1998), pp. 237-244.
ScienceDirect Materials Today: Proceedings 21 (2020) 1335–1339
www.materialstoday.com/proceedings
ICRACM-2019
Correlations between hardness and tensile strength of cracked aluminium plates repaired with composite patches Bishnupriya Dehuria, Shashwati Soumya Pradhanb,* a a
Civil Engineering Department, CAPGS, Biju Patnaik University of Technology, Rourkela, Odisha, 769015, India Civil Engineering Department, CAPGS, Biju Patnaik University of Technology, Rourkela, Odisha, 769015, India
Abstract The correlations between Rockwell hardness and tensile strength of cracked aluminium plates repaired with composite patches were studied. Composite patch on tensile strength of woven fabric, glass/epoxy composite laminates and the aluminium plates having 3 mm thickness of the three different crack length of 5 mm, 10 mm and 15 mm. Tensile tests of composite patch are performed on [0/90], in case of two lay-ups were used, viz. 4-ply and 6-ply. Under the hardness and tensile loading conditions, there is an important role of the reinforcement fraction and matrix strength in effecting the behavior of composite. The tensile test and hardness test are compared regarding the different loading modes. Result in a significant overestimation of the tensile strength of the hardness test, especially when the matrix strength is relatively low. The tensile strength of two materials is reduced while the difference in the hardness increases. © 2019 Elsevier Ltd. All rights reserved. Selection and peer-review under responsibility of SIXTH INTERNATIONAL CONFERENCE ON RECENT ADVANCES IN COMPOSITE MATERIALS, ICRACM-2019. Keywords:Composite; Hardness; Aluminium; Tensile strength
1. Introduction Hardness tests are most commonly utilized as a basic and successful method for the observation of the mechanical strength of metallic materials [1]. The interrelationship between different hardness scales and tensile strength has been arranged for a number of different types of alloy [2]. Composites shows significantly extreme utilization for purposes where quality control may be essential, it is necessary to correlate between hardness and
* Corresponding author. Tel.: +0-943-935-1426. E-mail address:[email protected] 2214-7853© 2019 Elsevier Ltd. All rights reserved. Selection and peer-review under responsibility of SIXTH INTERNATIONAL CONFERENCE ON RECENT ADVANCES IN COMPOSITE MATERIALS, ICRACM-2019.
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tensile strength in similar type of materials. After reinforcement composition the matrix allows is placed, the letter is denoted by the subscript ‘p’ as a particulate reinforcement. The researcher described the linear relationship between the Rockwell shallow-scale hardness and the ultimate tensile strength of the composite. For composites which have large reinforcement particles that might get fracture during the process of deformation. While in tension the fractured particles do not carry any applied load, they do not change accordingly the resistance to local compressive loading in hardness test. Experimental investigation [3] determined Griffiths micro hardness maps of cross-sections of high-pressure die cast test bars of AZ91. The specimens having rectangular cross-sections which are 1, 2 and 3 mm thick, or with a circular cross-section which is 6.4 mm in diameter, the hardness is higher near the edges and also more hardness was found near the corners of the rectangular specimens. While at the centre of the castings the hardness is generally lesser, due to a coarser solidification microstructure and the concentration of porosity. As per the result, it was found that the castings have harder surface the core. Though the hardness is not even on both sides of the casting, the layer is uncertain in hardness and depth. As the thickness of the bars decreases the average hardness increases which is derived by combining the micro hardness maps over the entire cross-section. The researcher [4] simplified the procedure of determination of mechanical properties such as hardness and the Young’s modulus of materials by improved the depth sensing indentation equipment. But sometimes it is difficulties to compute the accurate values of these properties. This is identified with, for example, the tip geometrical imperfections of the diamond pyramidal indenter and the definition of the contact area at the maximum load. Therefore, to determining the hardness and the Young’s modulus for the numerical simulation of ultra micro hardness tests can be a useful tool for better understanding. The software called HAFILM must produce to simulate the ultra micro hardness tests. Different mesh refinements were tested due to the dependence between the estimations of the mechanical properties and the size of the finite element mesh. By another method the yield stress of a metallic material can be formulated using Vickers hardness with taking account of residual stress. It is possible to evaluate the yield stress of bulk metal by a tensile test, but by surface modification methods it is not possible for local yield stress change, for examples, the peening technique which introduces high compressive residual stress at the surface. Therefore, by simple technique the local yield stress is being evaluated and thus the Vickers hardness test was conducted in this paper. The bonding between the residual stress and the Vickers hardness was experimentally examined as the Vickers hardness relies upon both the residual stress and the yield stress. As the test got satisfied for residual stress by above peening technique, so the yield stress of the surface could be evaluated from the Vickers hardness [5]. Researchers [6] were combining two independent studies of 7010 alloy plate and a rectilinear forging analyzed and took the parameters between Vickers hardness, yield stress and tensile strength. From these two studies, the hardness-yield stress data overlapped having general relationship. With the help of contact mechanics models constraint factors were calculated and evaluated. It observed by Shaw and DeSalvo was found to agree with the slope for the hardness–yield stress data. The y-intercept of the hardest–yield stress, relationship was explained by the work hardening, which was occurring during Vickers testing. The equation found to fit the hardness yield stress data for 7010 plate and forgings also provided a very respectable fit for a third independent study. Furthermore, an experimental equation was produced for the hardness–tensile strength relationship. Another research was [7] carried out tensile and impact tests and also hardness measurements on hot forged aluminium metal matrix composites to observe the effect of alloying element and forming process on their mechanical properties. Pure aluminium performs together with its composites for example Al4TiC, Al4Fe3C, Al4Mo2C and Al4WC were prepared utilizing an appropriate die-set get together on a 1MN capacity hydraulic press. Sintering procedure was conducted at 1200°C in an electric muffle heater for a holding time of 1h. Just after the sintering procedure the cylindrical performs were hot distored into a square cross-section bar of size (24 × 24 × 60) mm for preparing of tensile test and impact test samples according to the particular ASTM standards. The test samples of the standard tensile and impact test were fabricated from the forged square bar. The previously mentioned mechanical testing was conducted according to the standard ASTM methods. Furthermore, microstructural experiments on the hot forged square cross-section bar and hardness estimations were found and examined.
B. Dehuri and S.S. Pradhan / Materials Today: Proceedings 21 (2020) 1335–1339
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2. Experimental Procedures 2.1. Materials AA 1080 aluminium alloy sheets of 3 mm thickness were used in this experiment. The chemical composition of aluminium alloy is presented in Table 1. Commercially pure aluminium of varying graded of purity is used. These aluminium sheets can easily be formed and joined, but generally have the lowest strength characteristics of all the alloys. Glass fiber is a material, which consists of extremely fine fiber of glass. It is formed when thin strands of silica-based glass are extruded into many fibers. The glass fibers are easy to manufacture and in-expansive. E-glass is used as reinforcement material. Table 2 represents the properties of the patch materials. Table 1. Chemical composition of aluminium alloy. Element
Si
Fe
Cu
Mn
Mg
Zn
Ti
Weight Percentage
0.15
0.15
0.03
0.02
0.02
0.06
0.02
Table 2. Properties of Patch materials Properties
Inference
Tensile Strength
282.8 MPa
Compressive Strength
580.1 MPa
Density
2.58 g/cm3
Thermal Expansion (10-6/k)
8.82
Thermal conductivity
2.24 W/m.k
Softening point
846 0C
Melting Point
1121 0C
Hardness
435.113 Mpa
Bulk modulus
6.236 a
2.2. Details of Specimen
Fig. 1. Composite patch specimen after tensile test According to the ASTM standards, the specimens were prepared by slicing the aluminium sheets to the final dimensions, i.e. (250 x 30) mm and the patch thickness are 1.5 mm, 2.5 mm, 3.5 mm for tensile test. Both the sides of specimens have the gripping length 50 mm each and have gauge length of 150 mm. The specimens were tested at 25°C having crosshead speed 5 mm/min. The cracked plate which was repaired on only one side the surface was made according to the standard procedure for reinforcing a 4 ply and 6 ply composite patches. The hardness is assumed as a property of a material that helps it to resist plastic deformation by penetration. It also helps to resist bending, scratching, abrasion etc. To define the hardness, the standard Rockwell B-scale test was performed which have a 1.58 mm diameter spherical steel intender [8]. The hardness values are measured in the B-scale. The Rockwell B-scale hardness test is generally used to compute the mechanical strength of different kinds of aluminium
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alloy, because this method comprises of some good characteristic features like speed, reproducibility and the comparatively tiny size of the indentation. The minor and major load applied is 10 kg and 100 kg. The depth of indentation beyond the minor load directly determined the hardness value (HRB). 3. Results and Discussion In tension, fractured particles don’t carry any applied load; they don’t change the resistance to local compressive loading in a hardness test, resulting the hardness test can accordingly overestimate the total tensile strength of the composite [9]. Fig. 1 shows the composite patch specimen after the tensile test. The indented region is extensive in comparison to the size and space in between the particle. Therefore, the indentation estimates the total effect of the material and is comparatively unresponsive to confined impacts. A very small amount of cracked particles was found below or far from the indentation. The values obtained from the hardness and ultimate tensile strengths of the materials were included in the hardness and strength data in one plot. In Fig 2. the ultimate tensile strength, function of the hardness (HRB) is shown for the composites. The tensile strength of both the materials is decreased while the difference in the hardness increases. As per the result, it was found that the hardness testing method, which is utilized to measure, the tensile strength may not be useful to particle reinforced metal matrix composites. The converging curves in Fig. 2 shows that if the matrix strength is more, then the impact is decreased.
Fig. 2. Relationship between true ultimate tensile strength and Rockwell B-scale hardness of the composite 4. Conclusions The hardness values and ultimate tensile strength seem to be having same tendency. Two different studies using the crack aluminium alloy repaired with two different plies i.e. 4-ply and 6-ply is quite important and shows a general relationship between hardness and strength. The relationship doesn’t found to be exist between hardness and tensile strength, especially where the matrix strength is comparatively low. There is also significant role of reinforcement fraction affecting the hardness-strength relation. The relationship between tensile strength and Rockwell hardness was also developed. References [1] Chawla, K. kumar., Meyers, M. A. Mechanical behavior of materials. Upper Saddle River: Prentice Hall, (1999), pp. 217. [2] Aray, T., & Harper, S. ASM Handbook, ASM International, Materials Park, OH (1991). [3] Cáceres, C. H., Griffiths, J. R., Pakdel, A. R, Davidson, C. J. Microhardness mapping and the hardness-yield strength relationship in highpressure diecast magnesium alloy AZ91. Materials Science and Engineering: A, 402(1-2), (2005), pp. 258-268. [4] Antunes, J. M., Menezes, L. F, Fernandes, J. V. Three-dimensional numerical simulation of Vickers indentation tests. International Journal of Solids and Structures, 43(3-4), (2006), pp.784-806. [5] Takakuwa, Osamu, Y.Kawaragi, H.Soyama. Estimation of the yield stress of stainless steel from the Vickers hardness taking account of the residual stress. Journal of Surface Engineered Materials and Advanced Technology. (2013), 3(04), pp. 262. [6] Tiryakioğlu, M., J.Robinson, S.Guapuriche, M. A.,Y. Zhao, P. Eason, P. Hardness–strength relationships in the aluminum alloy 7010. Materials Science and Engineering: A,(2015), pp. 196-200.
B. Dehuri and S.S. Pradhan / Materials Today: Proceedings 21 (2020) 1335–1339
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[7] Narayan, Sumesh, A.Rajeshkannan. (2017). Hardness, tensile and impact behaviour of hot forged aluminium metal matrix composites. Journal of Materials Research and Technology, 6(3), (2017), pp. 213-219 [8] ASTM Standards, Designation E 18-93. Standard test methods for rockwell hardness and rockwell superficial hardness of metallic materials, 1993. [9] Shen, Y. L., E.Fishencord,,N.Chawla.. Correlating macrohardness and tensile behavior in discontinuously reinforced metal matrix composites. Scriptamaterialia, 42(5), (2000), 427-432. [10] Mochida, M.Taya, D.Lloyd. Fracture of particles in a particle/metal matrix composite under plastic straining and its effect on the Young’s modulus of the composite. Materials Transactions, JIM, 32(10), (1991), pp. 931-942. [11] Krajewski, P. E., J. Allison, J. Jones. The influence of matrix microstructure and particle reinforcement on the creep behavior of 2219 aluminum. Metallurgical and Materials Transactions A 24, no. 12 (1993): 2731. [12] Finot, M., Y. Shen, A. Needleman, S.Suresh. Micromechanical modeling of reinforcement fracture in particle-reinforced metal-matrix composites. Metallurgical and Materials Transactions A 25, no. 11 (1994): 2403-2420. [13] Shen, Y. L, M. Finot, A.Needleman, S. Suresh. Effective elastic response of two-phase composites. Act a metallurgic aetmaterialia, 42(1), (1994) 77-97. [14] Gupta, M. Effect of precipitation on the bulk hardness and the ultimate tensile strength of a 6061/SiC composite. High Temperature Materials and Processes, 17 (4), (1998), pp. 237-244.