Effect of semi-solid forging on microstructure and mechanical properties of in-situ cast Al-Cu-TiB2 composites

The present work deals with the effect of semisolid processing on microstructure and mechanical properties of Al-4.5% Cu - 5% TiB2 in-situ cast composites. The composite was prepared by flux assisted synthesis in which TiB2 particles were formed in-situ through an exothermic reaction between K2TiF6 and KBF4 halide salts. Al-4.5 wt% Cu alloy and Al-4.5% Cu-5% TiB2 composite samples were forged in semisolid state with 0.3 vol fraction of liquid. Semisolid forging was carried out for two forge reductions (30% and 50% forge reductions). Microstructure studies show that the semi-solid forging results in uniform distribution of TiB2 particles and Al2Cu particles in the composite. Further, TiB2 particles play a dual role as grain refiners as well as reinforcements of composites. EBSD and nano indentation studies shows that semisolid forging results in dynamic recrystallization of grains in the composite with significant grain refinement which leads to a marked increase in hardness and elastic modulus of the alloy as well as the composite.