Analytical and experimental investigation of the effect of SPS and hot rolling on the microstructure and flexural behavior of Ti6Al4V matrix reinforced with in-situ TiB and TiC

Ti6Al4V matrix composites reinforced by in-situ TiB whiskers and TiC particulates were processed by spark plasma sintering at 1100 °C. The cylindrical composite samples were hot rolled at 900 °C by 66% reduction of height. The flexural properties of the composites and the base alloy were investigated by three-point bending test. The microstructure and fracture surfaces of the samples were observed by optical and scanning electron microscopy. The results showed that although it was expected that the flexural strength of the composite samples increase by increasing the reinforcement content, it was deteriorated at higher reinforcement contents (equal or more than 1 vol% TiB-0.24 vol% TiC). The corresponding results of the rolled samples showed that the strengthening extends to reinforcement content of 1 vol% TiB-0.24 vol% TiC and then decreases. Moreover, the expected stress increments of composite samples produced by SPS and hot rolling, due to the thermal, Orowan and geometrically necessary dislocations were calculated. The comparison of strength of rolled samples after SPS indicated that there is good agreement between the experimental and the calculated results. However, there were instances of the reduction of the flexural strength that could be interrelated to the agglomeration of TiB whiskers.