Abstract
Titanium monoboride (TiB) whisker-reinforced titanium (Ti) matrix composites were produced by powder metallurgy, through vacuum sintering. TiB is formed by thermal decomposition of TiB2 precursor. In addition, a new hybrid composite was developed by admixing nanograined and nanocrystalline (more important) Ti to enhance the transformation mechanism of TiB2 to TiB phase. The morphology and particle size of the initial powders, mixtures and the microstructure of the composites have been studied by scanning electron microscopy (SEM). The phase analysis and transformation monitoring were performed by X-ray diffraction (XRD). The sintered composites were also subjected to compressive strength and hardness measurements. According to XRD results, through the addition of nanocrystalline Ti, a probable enhancement of the TiB2 → TiB transformation occurred producing more TiB whiskers in the hybrid composites. All samples of the hybrid composites exhibited improved yield strength (1365 MPa) and hardness (358 HV) compared to the non-hybrid ones 927 MPa and 254 HV, respectively.Graphical abstract
Highlights
Nowadays, metal matrix composites (MMCs) are becoming one of the most promising materials for applications requiring high specific strength and/or high ductility even at elevated working temperatures
The scanning electron microscopy (SEM) examinations of the powders revealed that the initial Ti particles have sponge-like structure and the (Fig. 3b) sizes agree with the nominal value, while the morphology of the TiB2 is platy and its particle size differs from its nominal size, varying between * 10 nm and 1–2 lm (Fig. 3a)
The X-ray diffraction (XRD) peaks of each phase can be identified on the patterns (Fig. 4); the deconvolution process of Rietveld refinement is required for quantitative calculations due to the overlapping of broadened peaks and severe texture produced by pressing and Titanium monoboride (TiB) crystallisation
Summary
Metal matrix composites (MMCs) are becoming one of the most promising materials for applications requiring high specific strength and/or high ductility even at elevated working temperatures. Since TiB2 has high mechanical properties (hardness, strength) and great thermal stability in absence of Ti, it is a promising candidate not just as matrix material, and as the reinforcement phase [5, 6]. Pairing Ti matrix with TiB2 for producing Ti-TiB whisker (TiBw)-reinforced type composites can be more beneficial [7]. Such Ti-TiB composites can be used in applications where products and workpieces with high-strength and lightweight are crucial factors [7]. As TiB improves mechanical properties of the composite [8], it can be applied in areas requiring high wear resistance (cutting and machining tools). Yi et al performed a comparative study between the composites of the TiTiB2-TiC system and composites of the Ti-B4C-C system, and the authors concluded that the composites of the Ti-TiB2 system always exhibited improved mechanical properties (elastic modulus, hardness, bending strength) than the composites of the Ti-B4C system [10]
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