Comparative Evaluation of Ex Situ and In Situ Method of Fabricating Aluminum/TiB 2 Composites

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Copyright  2020 American Foundry Society

Abstract In the present work, Al–TiB2 composites were casted using in situ and ex situ method of fabrication. The effect of processing temperature on the formation of titanium diboride particles was studied, and comparative evaluation of in situ and ex situ method was carried out. Characterization of composites was carried out to study the effect of various process parameters on the mechanical properties. The microstructure of in situ composites shows a homogeneous distribution of titanium diboride particles without agglomeration as compared to ex situ composites. SEM micrographs of in situ composites show distinct and reaction-free boundaries between reinforcement and matrix

material as compared to the ex situ composites. In addition, average UTS of in situ AlSi5Cu3/3%TiB2 composite and ex situ AlSi5Cu3/3%TiB2 composite increased by 80.13% and 39.72% as compared to pure AlSi5Cu3, respectively. The average hardness of in situ AlSi5Cu3/ 3%TiB2 composite and ex situ AlSi5Cu3/3%TiB2 composite casted in metal mold increased by 45% and 31.66%, respectively, as compared to pure AlSi5Cu3.


Various reinforcements like TiB2, TiC, Mg2Si, Al2O3, AlN, and ZrB2 have been synthesized using the in situ method.12,31,32,48 Most of the studies on AMCs involve the use of SiC and Al2O3 as reinforcement, but the major drawback of these is the formation of intermetallics, deteriorating the mechanical properties and chemistry of composites. The literature shows that to overcome these issues, thermodynamically stable reinforcement like TiB2 is more effective. Researchers have reported that TiB2reinforced composites have good mechanical properties compared to other reinforcements like TiC, Al2O3, B4C, and SiC.7,15,21,31,32,45 TiB2 has been used as the reinforcement material in AMCs due to its excellent properties like low density, higher Young’s modulus, high wear resistance, and high hardness.46 Moreover, TiB2 is more coherent with the aluminum matrix and has good wettability. Thus, TiB2 is one of the strong contenders for the development of AMCs.

Aluminum alloys are widely used in many engineering applications in the fields of automobiles where high mechanical properties such as hardness and tensile strength are required,5 while low ductility and poor tribological characteristics are limiting factors for wide range of applications. Aluminum matrix composites (AMCs) are established as a high-performance material due to its low density, good corrosion resistance, high damping capacity high electrical, thermal conductivities, and high mechanical properties.10,25 Thus, AMCs are gaining a lot of attention in the field of automobiles, aerospace, electronics, etc. The selection of matrix material and reinforcement phases along with processing techniques is crucial for developing AMCs. Researchers have developed AMCs by incorporating various reinforcements like SiC, Al2O3, B4C, TiC, AlN, ZrB2, TiB2.1,4,26,30–32,49

Received: 10 June 2020 / Accep