Abstract
In the present study, 98.6–99.5% dense in situ reinforced Ti6Al4V/TiB composites were manufactured with a newly developed approach based on hydrogen-assisted blended elemental powder metallurgy (BEPM). The approach includes the activation milling of titanium powder produced with hydrogenation-dehydrogenation (HDH-Ti powder) with finer TiB2 additives, following blending with TiH2 and master alloy (MA) powders, and final press-and-sinter operations. Scanning electron microscope (SEM) observations prove the formation of microstructures with improved density and homogeneous distribution of TiB reinforcements in a sintered Ti6Al4V matrix. Hardness and compressive tests validated the high mechanical characteristics of produced composites. The effect of preliminary milling time over 2–6 h and the ratio of hydrogenated and non-hydrogenated titanium powders used (TiH2 vs. HDH Ti) on microstructure and mechanical properties were studied to further optimize the processing parameters. Test results indicate the above approach can be regarded as a promising route for the cost-effective manufacturing of Ti6Al4V/TiB composite with reduced porosity, tailored microstructure uniformity, acceptable impurity level and, hence, mechanical characteristics sufficient for practice applications.
Highlights
Metal matrix composites are the subject of numerous studies [1,2,3,4,5,6]
Power blends after milling shown in Figure 3 demonstrated that finer and satellitelike TiB2 particles were tightly bonded on the surface of large HDH-Ti particles which were obviously deformed during milling
Ti6Al4V-TiB composites exhibiting up to 99.5% density were produced using powder blends based on TiH2 and HDH Ti powders with relatively sim
Summary
Metal matrix composites are the subject of numerous studies [1,2,3,4,5,6]. Particle-reinforced titanium matrix composites (PRTMCs) have been widely studied and have proved to be excellent materials for critical applications such as aerospace, defense and medical instruments due to isotropic homogeneity, improved modulus and high-temperature characteristics [1]. The employment of raw TiB2 or B powders as the boron source in BEPM processing resulted in the formation of excessive residual porosity in the titanium-based matrix during Ti+TiB2 →TiB or Ti+B→TiB reactions and inhomogeneous partially reacted reinforcements in sintered microstructures [14,15,16]. Another problem is that the achievement of fine TiB precipitations in sintered composites, because of coarse raw TiB2 particles or their agglomerations formed during powder preparation procedures, cannot be fractionized into dispersed ones. Previous work by current authors indicates that the hydrogen-assisted 2 stage press-and-sintering route can effectively transform the porous composites into nearly dense materials without hot pressing or hot deformation operations, but doubled powder preparation, compaction and sintering procedures induce risks for material contamination with atmospheric impurities and degraded ductile properties [17]
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