Silicide Precipitates. Titanium Matrix Composites Research

In this paper, the super-saturated Titanium alloy powder was prepared by mechanical alloy(MA). The diffraction peak of XRD for the powder was found deflected or linked with other peak when the powder was analysed. Furthermore, the change of DTA curve and parameter of Titanium crystal lattice made it clear that the cause for diffraction peak's change.The silicon atom was injected into Titanium lattice by MA , noncrystal and new crystal appear. This is the reason why the change happened in XRD diffraction peak and DTA curve. It indicated the MA manufacture was effected for the latter aging heat treatment.The flans with MA powder were heat-treated in high temperature in order to improve the silicon solution degree in Titanium matrix. During aging time, the precipitation appeared, but it didn't clear in short aging time, after 96 hours, it was big enough to be detected by EDX and the chemical composition of one silicides determined from EDX was: 35.17 at.%Si, 21.15at.%Ti,43.69 at%Zr. This type of silicide is very close to (TiZr)Si(S2) reported by N.Y.SALPADORY and H.M. FLOWER in 1995. In his paper, the conclusion for Ti/Zr atom was between 0.68 and 2. 26. and in our paper, the ratio is: 2.065. Another silicides' composition by EDX is: 46.46 at.%Si, 33.63at.%Ti, 19.90 at%Zr. This kind of composition was accorded with Bhoskaran's forecasted molecular formula: (TiZr)Si.Furthermore, the diffusion couple (DC) was done to find the way how the precipitation appeared and changed during long heat-treated time, and make sure the silicide precipitation' composition in flans. The conclusion was followed:First, the phenomenon for the fast diffuse elements was observed. Silicon play the role in this ternary elements: Titanium, Silicon, and Zirconium.Second, the formation element for the ternary silicide phase was controlled by Zirconium' diffusion. The following a serial of new phase in DC was given: Si/(Ti,Zr)xSiy/(Ti,Zr)Si/Ti5Si3/ TiSi /Ti3Si/Ti-alloyBy compare DC to the flans precipitation, the new found phase was accordedwith flans closely and considered the inaccuracy factor, the precipitation in flanswas decided to be (Ti,Zr)Si, the atom of Ti/Zr ratio was between 1.849 and 2.657.The precipitation in of Titanium matrix composite material is in the hot research field, especially for its stability. Through flans' long time heat-treated and DC research work , originally ,the new phase (Ti,Zr)Si was proved to be a stable phase in high temperature and distributed evenly in matrix. Therefore, as a precipitation , it maybe apply in particle reinforce titanium matrix material.