In-situ TiB/Ti-6Al-4V composites with a tailored architecture produced by hot isostatic pressing: Microstructure evolution, enhanced tensile properties and strengthening mechanisms

In-situ synthesized titanium borides reinforced Ti-6Al-4V composites with a tailored reinforcement architecture were successfully prepared by hot isostatic pressing (HIP) starting from a TiB 2 /Ti-6Al-4V powder system. The microstructure of the composite samples was investigated using X-ray diffraction (XRD) technique and scanning electron microscopy (SEM), and the mechanical properties were evaluated through room and high temperature tensile testing . It is found that during HIP the additive particles TiB 2 have totally transformed into TiB needles, which tend to decorate at prior particle boundaries of the consolidated powder particles to form a network structure. With increasing TiB 2 addition from 3 wt.% to 8 wt.%, the microstructural feature of the TiB network structure experiences the variations of discontinuous TiB reinforcement → quasi-continuous TiB reinforcement → continuous TiB reinforcement. The room temperature tensile properties of the composites are improved with increasing addition of TiB 2 from 3 wt.% to 5 wt.%, but the tensile strength of the sample with 8 wt.% TiB 2 drastically decreases. As to the high temperature properties, the titanium boride reinforced Ti-6Al-4V alloy composites can be an increased maximum service temperature by over 200 °C while retaining the same tensile strength accompanied with a suitable elongation. The strengthening mechanism is mainly attributed to the load-bearing transformation, grain refinement and dispersion strengthening.