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Method for producing titanium compound powder

wallpapers News 2021-02-04
Sponge titanium, which is almost pure titanium, is extremely ductile and difficult to process into titanium powder. One method of producing powder is the hydrogenated dihydrogen (HDH) process, in which sponge titanium is hydrogenated to fragile titanium hydride (TiH2). Titanium hydride is easily ground into powder and then dehydrated to form titanium powder.
In this work, titanium hydride powder obtained from sponge titanium was used as a raw material for mixing and mechanical alloying with elemental powder.
 
First, titanium hydride powder and aluminum element powder are mixed to produce a homogeneous powder, which is then compacted and sintered to produce powder metallurgy compacts.
Secondly, the titanium hydride powder and the aluminum element powder are mechanically alloyed and then compacted. Mechanically alloyed powders are characterized by particle size distribution, morphology and microstructure. In blending and mechanical alloying, the green body is characterized by evaluating the density of the green body, and the sintered body is characterized by the sintering density, microstructure and hardness. Both methods lead to the formation of TiAl3 intermetallic compounds.
It has been determined that through simple mixing and homogenization, titanium hydride can be used as a starting material for the production of powder metallurgy components, where similar to metal foam, porosity is beneficial rather than problematic.
From the products obtained in the TiH2-Al system, titanium hydride can be used as a precursor for mechanical alloying. However, the formation of complex hydrides may introduce harmful properties, requiring further research. In order to produce non-porous components, it is recommended to dehydrogenate TiH2 powder before grinding, that is, to produce titanium powder by the hydrogenated dihydrogen (HDH) method.
 
Titanium aluminide Ti3Al and TiAl were synthesized by using TiH2 + Al powder mixture. The phase transition and the synthesis of titanium aluminide after the decomposition of titanium hydride in a vacuum and inert gas have been studied. The results show that the use of titanium hydride instead of titanium in the powder mixture with aluminum significantly activates the diffusion process and leads to accelerated production of single-phase titanium aluminide under isothermal heating. This is due to the small size of the charge, the high density of defects in the titanium and aluminum lattices (including those caused by hydrogen phase hardening), and the reduction of the Al2O3 film that may be caused by atomic hydrogen.
 
The type of atmosphere does not significantly affect the rate of phase formation, but it seems more practical to perform the synthesis in a vacuum because hydrogen is completely removed while forming aluminides at the same time. Due to the fact that aluminum completely reacts with titanium in the solid-state, a final product close to the theoretical density is obtained without applying high pressure.

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