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1 Ravi Shankar Raman 523 Research Article Nov 2011

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Mechanical Properties of Stirr Cast Hypoeutectic Al-Si Alloys
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  Available ONLINE www.vsrdjournals.com  VSRD-MAP, Vol. 1 (3), 2011, 96-103    ____________________________ 1,2 Associate Professor, Department of Mechanical Engineering, ABES Engineering College, Ghaziabad, Uttar Pradesh, INDIA. *Correspondence : ravi.raman21@gmail.com   R R R EEESSSEEEAAAR R R CCCHHH AAAR R R TTTIIICCCLLLEEE  Mechanical Properties of Stirr Cast Hypoeutectic Al-Si Alloys 1 Ravi Shankar Raman* and 2 K. V. Ojha ABSTRACT The manufacturing process through stirr casting leads to give near-net-shape and fine grain microstructure. In this process Si particles, which are not distributed uniformly in conventional casting process, are distributed uniformly throughout the casting. In the present study stirr castings were made of Al-7Si, Al-10Si and Al-12Si alloys and then their Mechanical properties and casting properties were studied. Microstructure of stirr casted formed alloys showed equiaxed grains morphology in contrast to as cast alloys. The mechanical properties of Al–12 Si alloy were found to be better than that of the Al-7Si and Al-10Si.  Keywords :    Stirr Casting; Mechanical Properties; Microstructure. 1.   INTRODUCTION Aluminium- Silicon alloys are widely used in aerospace, automobile and electronic industries due to their light weight, high strength to weight ratio, excellent wear and corrosion resistance, good casting ability and low coefficient of thermal expansion [1]. The Silicon phase in aluminium- Silicon alloy provides it all aforementioned properties. But in conventional casting process coerse Silicon phase is formed which leads to  poor mechanical properties. Therefore, Stirr Casting is required to enhance the mechanical properties [1,2] Stirr casting, which is a rapid solidification process increases the solubility of Silicon in Aluminium and also modifies the morphology of Silicon Phase. Mechanical properties of Aluminium – Silicon Stirr casting alloy  produced at various compositions were studied [3, 4]. In the present work, hypoeutectic Aluminium- Silicon alloys with compositions Al-7Si, Al-10Si and Al-12Si were stirr casted for the study of various mechanical properties.  Ravi Shankar Raman et al   / VSRD International Journal of Mechanical, Auto. & Prod. Engg. Vol. 1 (3), 2011 Page 97 of 103 2.   RESEARCH METHODOLOGY 2.1.   Alloy Preparation For the experimental set up of Al-Si percentages are maintain with weight as per the given set and alloys are  prepare on the basis of weight ratio (a) Al-93%, Si-7% (b) Al-90%, Si-10% (c) Al-88%, Si-12 % 2.2.   Procedure 2.2.1.   Setup 027064 - Al 7424-905 grade Laboratory aluminium powder and 030066- Si 7440-21-3 MW-28.09 grade Laboratory silicon powder are mixed in dry state. After proper mixing of Al-Si powder in a single crucible as  per the given weight ratio. The molten metal is properly mixed with steel rod due to that temperature losses are occurred so for maintaining the fluidity and viscosity of mixture crucible is reheated up to 1370 o C and moulded in crucible with nitrogen sealded head upto 1430 o C and casted on three different stages ( sand , ferrous and non ferrous casting ). 12 to 24 hours used for solidifying for the casting material then sample is used for the investigation of mechanical Properties [1,3]. Three sets of mould were prepared for the casting which is mentioned below:    Sand    Ferrous     Non ferrous Table 1: Percentages of Al- Si mixture and Casting Code Sl.No. Percentages of Al – Si mixture Type of Casting Casting code 1. Al-93%, Si-7% Sand Casting 1 / 1 Al-93%, Si-7% Ferrous Casting 1 / 2 Al-93%, Si-7% Non ferrous casting 1 / 3 2. Al-90%, Si-10% Sand Casting 2 / 1 Al-90%, Si-10% Ferrous Casting 2 / 2 Al-90%, Si-10% Non ferrous casting 2 / 3 3. Al-88%, Si-12 % Sand Casting 3 / 1 Al-88%, Si-12 % Ferrous Casting 3 / 2 Al-88%, Si-12 % Non ferrous casting 3 / 3 Once casting work is over then we go for investigation of casting defects. For verify the visual inspection of all the above casting then we analyse that the outer structural of the ferrous casting is comparatively smoother than the others castings like sand and non ferrous casting. To know about the casting defects we use for Non-destructive testing like ultrasonic testing for all the casted materials.  Ravi Shankar Raman et al   / VSRD International Journal of Mechanical, Auto. & Prod. Engg. Vol. 1 (3), 2011 Page 98 of 103 2.2.2.   Hardness Testing of the Specimens For hardness testing of the specimen same test piece is used, since aluminium is a ductile material so britnell hardness, B grade of scale is used for testing. For this use the 1.5mm diameter Indentor and 100 kgf load is used, after applying the load the hardness is calibrated for each and every specimen. 2.2.3.   Ultimate Tensile Strength of the Specimens Ultimate tensile strength is the maximum stress that a material can withstand while being stretched or pulled  before necking, which is when the specimen's cross-section starts to significantly contract. The Ultimate tensile strength is usually found by performing a tensile test and recording the stress versus strain; the highest point of the stress-strain curve is the UTS. It is an intensive property; therefore its value does not depend on the size of the test specimen. However, it is dependent on other factors, such as the preparation of the specimen, the  presence or otherwise of surface defects, and the temperature of the test environment and material. 3.   RESULTS 3.1.   Specimen Nomenclature The Silicon based aluminium was casted. For recognition of specimen easily a code was self generated which is illustrated in Table 2. Table 2 : Specimen Code Sl. No. Heat No. / Sample No. Process of Mould 1. 1/1 Sand 2 1/2 Ferrous 3 1/3 Non ferrous 4. 2/1 Sand 5 2/2 Ferrous 6 2/3 Non ferrous 7. 3/1 Sand 8 3/2 Ferrous 9 3/3 Non ferrous 3.2.   Non Destructive Testing Six inch long and 1.5 inch diameter specimen are tested for to knowing about the casting defect and primary stage of grain structure of the alloys. The following results are absorbed. Table 3 : Performance of Specimens Tested through Non Destructive Testing Sample no. Performance 1/1 Poor 1/2 Good 1/3 Good 2/1 Appreciable 2/2 Good 2/3 Very good 3/1 Good 3/2 Very good 3/3 Excellent  Ravi Shankar Raman et al   / VSRD International Journal of Mechanical, Auto. & Prod. Engg. Vol. 1 (3), 2011 Page 99 of 103 From the NDT test sample, sample no 3/3, 3/2, 2/3, 3/2, 2/1 has good backwell so that above sample are assumed to free from casting defect and have good grain structure 3.3.   Spectrometer Testing Of The Specimens Weight % of element ingredients of the test specimens are as follows Table : Weight % of element ingredients ELEMENT  NAME SAMPLE NUMBER 3/3 2/3 1/3 Al 86.64 88.48 92.12 Si 12.23 10.20 6.80 Fe 0.273 0.255 0.212 Cu 0.150 0.160 0.124 Mn 0.009 0.012 0.019 Mg 0.029 0.038 0.046 Zn 0.062 0.008 0.019 Ti 0.010 0.000 0.014 3.4.   Hardness of the Specimens From the hardness testing of all specimens the following data of hardness are recorded as shown in Table 4. It was found that when the % Si is increased the hardness of the specimen is increased and it is independent of the variation of % Al content. Table 4 : Hardness Testing Sample  No. Aluminium % Silicon % Rockwell Hardness No. (HRB) 1/1 93 6.8 46 1/2 93 6.8 50 1/3 93 6.8 52 2/1 90 10.2 57 2/2 90 10.2 58 2/3 90 10.2 61 3/1 88 12.23 63 3/2 88 12.23 67 3/3 88 12.23 70 Fig. 1 : Variation of Hardness Curve 020406080(1/1) (1/2) (1/3) (2/1) (2/2) (2/3) (3/1) (3/2) (3/3)    V   a    l   u   e   i   n   H   R   B   &   i   n   %   S   i    l   i   c   o   n SampleVariation of Hardness with Silicon % SILICON %HARDNESS( HRB)
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