Effect of Mechanical Activation on the In Situ Formation of TiB2 Particulates in the Powder Mixture of TiH2 and FeB

Abstract

The in situ formation of TiB 2 particulates via an interface reaction between Ti and FeB powders was studied. The effects of mechanical activation by high-energy milling on the decomposition of TiH 2 and the interface reactions between Ti and FeB powders to form TiB 2 were investigated. Powder mixtures were fabricated using planetary ball-milling under various milling conditions. The specific ball-milling energy was calculated from the measured electrical power consumption during milling process. High specific milling energy (152.6 kJ/g) resulted in a size reduction and homogeneous dispersion of constituent powders. This resulted in a decrease in the decomposition temperature of TiH 2 and an increase in the formation reaction of TiB 2 particulates in the Fe matrix, resulting in a homogeneous microstructure of nanoscale TiB 2 evenly distributed within the Fe matrix. In contrast, the powder mixture milled with low specific milling energy (36.5 kJ/g) showed an inhomogeneous microstructure composed of relatively large Fe-Fe 2 B particles surrounded by a thin layer of Fe-TiB 2 within a finely dispersed Fe-TiB 2 matrix region.

Archives of Metallurgy and Materials

“…Figure 3 shows a secondary electron image and a backscattered electron image of the polished cross-section of the ex-situ processed powder compact sintered at 1150 o C for 10 minutes with 99.6% relative density. We observed three phases with different gray levels, as reported in our previous works [12,13]: dark gray, gray, and bright gray. The dark-gray phase was TiB 2 containing the B element with a small atomic number of 5, while the bright-gray phase was relatively large Fe-powders with the atomic number of 26.…”

“…Most areas were composed of the gray phase, which contains Fe and TiB 2 . The bright-gray area is comprised of Fe-rich particles [13].…”

“…The in-situ powder was prepared under the same milling condition and then heat-treated at 900 o C for 2 h under flowing argon gas in a tube furnace to form TiB 2 particulates through a reaction between FeB and Ti. More details of the fabrication process of the (FeB, TiH 2 ) powder mixture can be found in our previous works [12,13].…”

“…We have also reported that Fe-TiB 2 composite powder with TiB 2 particulates smaller than 5 nm could be synthesized in-situ by planetary ball milling and subsequent heat treatment of an iron boride (FeB) and titanium hydride (TiH 2 ) powder mixture [12]. The effect of mechanical activation on the in-situ formation of TiB 2 particulates in the powder mixture of TiH 2 and FeB has been reported, and the interface reactions between Ti and FeB powders were explained in detail [13].…”

Powder metallurgy processed TiB2-reinforced steel matrix composites: a review

“…Huynh et al. [119] adopted a similar procedure for development Fe–TiB 2 composite powder and also investigated the effect of mechanical activation on the in situ formation of TiB 2 particles by an interfacial reaction between Ti and FeB powders.

Figure 7 Gibbs free energy as a function of temperature.

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