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9 Titanium(insert)/aluminium–siliconTi/Al–7SiInsertmouldingProceedings of the National Conference onTrends and Advances in Mechanical Engineering,YMCA University of Science & Technology, Faridabad, Haryana, Oct 19-20, 2012approaches to joining light metals• Bimetallic specimen test piecesof an AS-7 matrix locallyreinforced with a titanium insertthat have been produced using anexperimental procedure allowingthe control of both the interfacialreaction layer and themetallurgical health of the matrix(directional solidification).• The results obtain under push-outsolicitation highlight the potentialof the joining process forproducing castings with highmechanical performances.• Push-out test and avariant that is thecircular-bending testto investigate themechanical strength.• Characterization ofthe interfacial zoneby OpticalMicroscopy (OM),Scanning ElectronMicroscopy (SEM)and ElectronMicropobe Analyses(EPMA).• When a chemical bond isestablished at the Ti/AS-7interface an important rise ofmechanical properties for thebimetallic assembly is observed:the mean shear strength value isabout 120 MPa whereas it is of48 MPa for simply frettedspecimens.• Finite ElementModeling (FEM)was performed todescribe the stressdistribution in abimetallic sliceduring push-out testat different loadlevel.• A three steps failure sequenceproposed is both characterized bycrack propagation from bottom totop and matrix yielding from topto bottom.10 S45C steelinsert tocopperCastwelding orcompoundcasting• Heat treatment formed reactedlayers in the interface. The layernear the S45C steel matrix wasthe cast welding layer; anotherclose to the copper matrix wasthe irregular layer, and the otherbetween these two layers was themiddle layer.• The microstructureof the compoundcasting wasobserved by OM(optical microscope)and SEM (scanningelectronmicroscope).• EPMA proved that most of theiron atoms diffused into thecopper matrix and only a fewcopper atoms diffused into theiron matrix during diffusionoccurred between two matrices.X-ray diffraction showed that thechemical compounds of theinterface were CuFeO2 and C.• Furnace-cooling yielded thelargest interface shear strength,and water quenching yielded theleast.The fractured region wasnear the S45C steel matrix in thecast welding layer.• The interface phasewas analyzed by X-ray diffraction andthe composition wasdetermined usingEDS and EPMA(electron probemicro-analysis).• A push-out test wasused to determinethe interface shearstrength508
Proceedings of the National Conference onTrends and Advances in Mechanical Engineering,YMCA University of Science & Technology, Faridabad, Haryana, Oct 19-20, 20125. Gaps in Existing LiteratureA limited work is done on compound casting processes till now. In many cases, one material alone does notsatisfy the requirements of lightweight constructions, and dissimilar joining between two metals must be needed.A variety of attempts have been dedicated to joining meals and alloys using different fusion welding and solidstatejoining methods such as tungsten inert gas welding, laser welding, friction-stir welding, and vacuumdiffusion bonding. The major problem in these joining processes is the formation of much more intermetalliccompounds with a very high hardness and brittleness between two meats as an interlayer, which is deleterious tothe mechanical properties. However, solid-state joining processes such as friction-stir welding and vacuumdiffusion bonding can achieve relatively higher joining strengths compared to fusion methods, due to eliminationof defects like shrinkage, porosities and inclusions. In addition, long process time and high correspondingoperating cost of the vacuum diffusion bonding and specific requirements for the shape of the substrate infriction-stir welding may render these solid-state joining processes not easy for practical and industrialapplications. Microstructure and EDX (energy dispersive x-ray) analysis are performed by some scientists/researchers but Differential Thermal Analysis are not performed. Optimization of process parameters ofcompound casting w.r.t. mechanical properties such as tensile strength, hardness, elongation and impact strengthetc. is not reported in literature till now.6. ConclusionIt may be concluded from above studies that:• The compound casting process presents a solution for meeting the demands of a specific application,particularly in light weight constructions.• The compound casting is the process which meets a wide range of requirements within one componentby combining different materials.• It is possible to make light metal compound cast parts using the combination of light metals like Al-Al,Mg-Mg and Al-Mg, Ti-Al, Cu-steel and Cu- grey cast iron etc.• It is necessary to remove the natural oxide layer for complete diffusion at interface between solid andmelted metal.• The zincate process followed by Zinc electroplating is the best way to remove the effect of oxide layerat the interface.• Formation of the interface in the compound casting process is diffusion controlled and usually theinterface consists of three different layers.• Heat treatment formed reacted layers in the steel-copper interface. Furnace-cooling yielded the largestinterface shear strength, and water quenching yielded the least.• The heat treatment results in an improvement of the mechanical properties of the AS7G matrix itselfwhen applied to Ti/AS7G assemblies. A significant increase of the load level characteristic for damageonset is observed.7. References[1] E. Hajjari, M. Divandari,S. H. Razavi,S. M. Emami,T. Homma,S. Kamado,(2011) “Dissimilar joining ofAl/Mg light metals by compound casting process.”, Journal of Material Science 46:6491–6499.[2] O. Dezellus, M. Zhe, F. Bosselet, D. Rouby, J.C. Viala,(2011) “Mechanical testing of titanium/aluminium–silicon interface: Effect of T6 heat treatment.”, Materials Science and Engineering A 528, 2795–2803[3] M. Rübner, M. Günzl, C. Körner, R.F. Singer,(2011) “Aluminium–aluminium compound fabrication by highpressure die casting.”, Materials Science and Engineering A 528, 7024– 7029[4] K.J.M. Papis, J.F. Löffler, P.J. Uggowitzer, (2010)“Interface formation between liquid and solid Mg alloys—An approach to continuously metallurgic joining of magnesium parts.”, Materials Science and Engineering A527, 2274–2279.[5] M. Mehdi Hejazi, M. Divandari, E. Taghaddos, (2009)“Effect of copper insert on the microstructure of grayiron produced via lost foam casting.”, Materials and Design 30, 1085–1092[6] Konrad J. M. Papis, Joerg F. Loeffler & Peter J. Uggowitzer,(2009) “Light metal compound casting.”,Sciencein China Series E: Technological Sciences, vol. 52, no. 1, 46-51[7] M. Paramsothy, N. Srikanth, M. Gupta,(2008) “Solidification processed Mg/Al bimetal macrocomposite:Microstructure and mechanical properties.” Journal of Alloys and Compounds 461, 200–208[8] K.J.M. Papis a, B. Hallstedt b, J.F. Lo¨ffler a, P.J. Uggowitzer, (2008)“Interface formation in aluminium–aluminium compound casting.”, Acta Materialia 56, 3036–3043.509
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