- Open Access
- Authors : Ranjitha P, Dr. Ajaykumar B. S , Dr. Saravanabavan D
- Paper ID : IJERTCONV9IS15024
- Volume & Issue : NCRAEM – 2021 (Volume 09 – Issue 15)
- Published (First Online): 21-09-2021
- ISSN (Online) : 2278-0181
- Publisher Name : IJERT
- License: This work is licensed under a Creative Commons Attribution 4.0 International License
Effect of Cryogenic Treatment on Hardness and Tensile Strength of AlSic-B4C Composites
Ranjitha P.1, Dr. Ajaykumar B. S.2 , Dr. Saravanabavan D3
1Assistant professor, Department of Mechanical Engineering, DSCE, Bangalore, Karnataka, India.
2.Professor, Department of Mechanical Engineering, K.S.I.T., Bengaluru, Karnataka, India.
3 Associate Professor, Dept. of Mechanical Engineering, DSU, Bengaluru, Karnataka, India.
Abstract:- Aluminium alloys have low density and good mechanical properties, better corrosion resistance and wear, low thermal coefficient of expansion as compared to conventional metals and alloys. Hence they are widely used in aerospace and automobile industries. The admirable mechanical properties of these materials and their relatively lower production cost make them suitable for a variety of applications both from technological and scientific viewpoints. In the present investigations an attempt has been made to know the effect of cryo treatment on Thermal Conductivity, Hardness, Tensile strength, Deep cryo treatment on Al-6061 reinforcing with varying SiC and B4C contents. The composite is manufactured throughastircastingprocessinanelectricmeltingfurnace.The experimental study is performed by varying the weight percentage of Silicon carbide powder and boron carbide with pouring temperature and stirring time asconstant.
Keywords: Aluminium Metal Matrix Composite, Stir Casting, Reinforcement Silicon Carbide and BoronCarbide, Taguchi Method
Nowadays, with the modern development need of developments of advanced engineering materials for various engineering applications goes on increasing. To meet such requirements metal matrix composite is one of trustworthy sources. Composite material is one of the reliable solutions for such situations. In composites, materials are blended in such a way, to enable us to enhance the use of their parent material while minimizing to some extent the effects of their deficiencies. The simple term composites gives indication of the combinations of two or more materials in order to improve the properties. In AMC one of the constituents is aluminum, forms a percolating network and is known as matrix phase. The other constituent is embedded in this aluminum and serves as reinforcement, which is usually non metallic and commonly ceramic such as SiC, Al2O3,B4C etc.(1,2,3,4) Al 6061 is fairly a well liked choice as a matrix material to prepare MMCs owing to its better formability characteristics. It is widely used in numerous engineering applications including transport and construction where superior mechanical properties such as tensile strength, hardness etc. are essentially required.(6,7)
To further increase the properties of these composites, processes like heat treatment for whole material and surface processing are also carried out. On the other hand cryogenic treatment also known as sub zero treatment is done. It is an ancient process and widely used for the high precision parts and
objects, especially for the ferrous and tooling materials earlier(8). The subjecting of the material to extreme cold hardens, strengthens and molecular alignment in the micro level is fine and smooth the material has longer life (9). Now the cryogenic treatment which is whole material treatment is widely used in many automotive, aerospace, electronic and mechanical engineering industries to improve mechanical strength and dimensional stability of components For the past few years the cryogenic treatment for the nonferrous metals such as aluminium and magnesium alloys has been done for the their improvement of properties (10). The improved mechanical properties and microstructure changes of the metals and alloys in cryogenic processing drew the attention of researchers towards this process. The researchers (11, 12, 13, 14) showed the beneficial effects of cryogenic treatment on nonferrous metal aluminium. The effect of cryogenic treatment on the wear performance of copper alloy showed least significant changes (15). This led to the idea of analyzing the properties when MMCs are undergoing cryogenic treatment. This field is rapidly growing and is used by many manufacturers. The present work intends to build a facility to research the process and results of the cryogenic treatment. This helps to create standards for both processing and testing that are currently unavailable. Hence it gives the significance that mechanical properties of the MMCs developed are evaluated at cryogenic temperatures. Thus in this experimental work cryogenic treatment was applied to Al6061/SiC MMCs to study its effect on , Hardness, and Tensile strength
2.0. EXPERIMENTAL SET UP AND PROCEDURE AlSiC-B4C composite are for combination of 1, 2, 3 and 4%
SIC are casted by using stir casting process for combination of 1, 2, 3 and 4% SIC are casted by using stir casting process.(4) Then the jobs are subjected for Deep cryo treatment process. The jobs are cooled down to Deep Cryo Temperature -1960 c at a rate of 30c/min from room temperature in computerised Cryo Processor, soaked at that temperature for a period of 24 Hrs and then brought back to room Temperature at a rate of 30c/min. then the Deep Cryo Treated specimen tested for various Properties and compared with Untreated samples.
2.1 Hardness test.
Brinell hardness has been determined for reinforced alloy and hybrid composites developed using Al 60613wt. % as the alloy with the SiC and B4C particles added as reinforcements in amounts of 1, 2, 3 and 4 wt.% respectively.
The Brinell hardness has been measured for unreinforced alloy and cast composites with 5 mm hardened steel ball indenter of 250 Kg load was applied for 30 seconds on a
sample and then the diameter of indentation was measured with help of the tool makers microscope.
For each indentation, an average of two diameters measured perpendicular to each other was used to obtain the corresponding hardness. On each sample at-least eight indentations for hardness measurement were made at different locations and the average of these readings is reported as the average hardness value of the material. Brinell hardness number has been found out by using Standard formulae.
Fig 1: Indicating the variation in hardness number for different percentage of SiC+B4C particles
Fig 2: Bar chart shows variation in BHN between Untreated and Deep Cryotreated AlSiC+B4C Composites.
From fig (1) and fig (2) indicates that as the percentage of SIC increases hardness value also increases. But Deep Cryotreatment on composites has helped in increasing the hardness on composites due to Improvement in wear resistance This is in concurrence with the investigation has carried out by Earlier investigators.(11,12,13,14,15)
As the percentage of B4C increases from 1% to 4% the hardness also correspondingly increases upto 2% and then decreases in case of treated and untreated one.
The hardness value does not change for AlSiC+4%B4C for untreated and treated once, but hardness has been decreased for the presence of 2% and 3% B4C on AlSiC except 1% B4C.
The effect of 2% B4C and 4% B4C has indicated the same treatment in case of tensile strength. The above findings or in concurrence with the investigations on above set composites.
2.1 Tensile test.
Tensile test is carried out on UTM as per standard procedure on below tensile test specimen as indicated in fig (4) and values are recorded at maximum load bearing capacity of the job and correspondingly tensile strength has been assessed by using formulae.
Fig. 3: Schematic representation of tensile specimen ASTM E8 standard2>
Fig. 4: Indicating the variation in tensile strength for different percentage of SiC+B4C particles
NCRAEM – 2021 Conference Proceedings
Fig 5: Bar chart shows variation in tensile strength between Untreated and Deep Cryotreated AlSiC+B4C Composites
From fig (4) and fig (5) indicates that as the percentage of SIC+B4C increases tensile strength also decreases. But deep Cryotreatmen helps in improving toughness on composites, which in turn has reduced the tensile strength on composites without incurring loss to its hardness property.
As the percentage of B4C increases from 1% to 4%, tensile strength also correspondingly increases up to 2% and then decreases beyond 2% in case of untreated composites.
A peculiar behavior has been observed correspondingly to deep cryo treatment on above set composites. The tensile strength, yield load and yield strength has been increased in comparison with the rest of the percentage of B4C on composites. Deep cryo treatment AlSiC+4%B4C composites can be used on those components where cushioning effect is predominant. Elongation also has been increased for above set composites by an amount of 5% in comparison to untreated one.
Tensile strength has been found to be moved (TS: 136.185Mpa) for untreated AlSiC+2%B4C composite in comparison with deep cryo treatment (TS: 131.746Mpa) on it. But yield load and yield strength has been found to be less in comparison with AlSiC+4%B4C composites. The above combination can be used on those components where ductility is predominant.
The aluminium metal matrix composites have been produced successfully by the addition of 1, 2, 3 and 4 wt.% of Silicon carbide (SiC+B4C) powder to molten Al 6061 alloy by liquid stir casting method followed by casting in permanent mould. The influence of increasing amounts of SiC+B4C powder addition has helped in increasing the mechanical properties.
The conclusions of the present study are outlined below.
Stir casting technique (Liquid Metallurgy) was successfully adopted in the preparation ofAl6061 SiC+B4C alloy and composites containing 1, 2, 3 and 4 wt. % of SiC+B4C powder reinforcement
The variation in tensile strength, yield load and yield stress and hardness value for 2%, 4% B4C on AlSiC composites provides guidelines for the use of deep cryo treated 2% B4C and 4% B4C depending upon its applications on components to be used for manufacturing the product.
The authors whole heartedly express gratitude to the Chemical and Metallurgical analysis lab and mentors in executing the research work
Funding: This research received no external funding
Conflicts of Interest: The authors declare no conflict of interest
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