The Preparation Of Porous Niobium And Its Infiltration With Ti-Al Intermetallic Compound

The porous layered interconnection niobium preform, in which the volume fraction of niobium was5%,10%,15%and20%respectively, was prepared by freeze drying process. The drying sublimation process of the preform was numerical calculated based on some related models. And the simulation results were applied to the experiment of niobium preform preparation. A preliminary study about the niobium preform infiltrated with TiAl alloy by pressureless infiltration using a vacuum induction melting furnace was also investigated in this paper.The three dimensional structure, the morphology, and the phases of the preform and the Nb/TiA1composites were characterized by using SEM, XRD. The investigation results indicated as follows:(1) The Nb preform with layered interconnection structure can be obtained or prepared by liquid nitrogen or freezer through controlling the sedimentation rate of the niobium particles in the slurry appropriately.(2) The test results of density and porosity of the Nb preform showed that the Nb preform can possessed of up to80%porous porosity while using the freeze-drying process. The microstructures of the niobium perform could be effectively controlled by changing the additive content, the slurry concentration and the cooling rate during the preparation. And the preforms with different porous structure and different volume fraction can be obtained.(3) The experimental tests and the numerical calculation of the preform drying process show that the preform drying efficiency is mainly related to the interior temperature of the freezer and the volume fraction of niobium. It seems that the higher the temperature is, the higher the drying efficiency of the preform is in case of the preform does not collapse. The additives and the preform freezing temperature take little effect on the drying efficiency.(4) The SEM and XRD analysis results indicated that the TiAl alloy was infiltrated into the Nb preform obviously under the action of the capillary force, and the Nb/TiAl composite was formed by pressureless infiltration.