The Peculiarities of Structure Formation Upon Sintering of TiH2+TiВ2 Powder Blends

Abstract

The investigation results on peculiarities of phase and structure formation as well as sintering kinetic of compacted TiH2 - TiВ2 powder blends. It was shown, the most intensive shrinkage upon heating took place within temperature range of TiH2 dehydrogenation (400 ÷ 650 0С). Heating of powder blend up to sintering temperature (1350 0С) resulted in formation of acicular TiB particles in titanium matrix, the amount of particles is increased with increase in exposure to 20 min. The longer duration of isothermal exposure did not lead to increase in amount and size growing of TiB particles. X-ray analysis of sintered TiН2+TiВ2 powder blend demonstrated the presence of titanium matrix phase, orthorhombic TiВ phase, and traces of Ti-B compounds of different concentrations (Ті3В4 and Ті2В5). The dilatometric investigations proved that addition of boride compounds and increase in boride content in powder blend led to decrease in shrinkage upon sintering as compared to shrinkage of single TiH2 powder compacts.

Microstructural Characteristics of Ti‐Based Composites with Various Ceramic Reinforcements Manufactured via Hydrogen‐Assisted Blended Elemental Powder Metallurgy

“…Furthermore, the presence of partially reacted intermediate boride phases and the agglomeration of coarse boride reinforcements, together with excessive porosity of the sintered MMCs, resulted in degradation of their mechanical properties. [33,34] As an advanced method to produce nearly dense Ti/TiB MMCs with evenly distributed TiB reinforcements, a two-stage hydrogen-assisted press-and-sinter powder approach was described by our earlier study. [35] In this method, hydrogenated powders were used in both sintering cycles for dual implementation of positive effect of hydrogen on the densification and purification of powder compacts.…”

“…Furthermore, the presence of partially reacted intermediate boride phases and the agglomeration of coarse boride reinforcements, together with excessive porosity of the sintered MMCs, resulted in degradation of their mechanical properties. [ 33,34 ]…”

In Situ Ti6Al4V/TiB Composites Prepared by Hydrogen-Assisted Sintering of Blends Containing TiH2 and Ball-Milled Ti+TiB2 Powders

“…Unfortunately, for BEPM manufacturing of composites reinforced with in situ formed TiB particles, a positive influence of TiH 2 →Ti transformation on activated densification usually is not observed. The employment of raw TiB 2 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+TiB 2 →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 TiB 2 particles or their agglomerations formed during powder preparation procedures, cannot be easily fractionized into dispersed ones.…”