| It is vital to manufacture lower cost, high performance titanium-based powder metallurgy materials. In this thesis, warm compaction and the surface shape of loading powder have been studied. Powder designed for warm compaction is fabricated from titanium powder and Ti-6A1-4V powder.Both characteristics and densification mechanism of warm compaction have been researched. The results show that the green density does not increase linearly with compaction temperature. At the optimum temperature of 140℃, the green density will be highest. The compacts density of titanium powder and Ti-6A1-4V powder by warm compaction can reach 3.72g.cm-3 and 3.62g.cm-3 respectively after being pressed at 500MPa. Compared to room compaction, the increase in green density are 0.21and 0.18 g.cm-3, respectively. The relation of green density and compression force is consistent with Kawakita's powder compaction equation in warm compaction. The ejection force of warm compaction is 26% lower than that of cold compaction after being pressed at 500MPa.Researches on the dynamic compacting curve of titanium powder, ejection force curve, X-ray diffraction, micro-hardness and microscopic structure of compact results show the densification mechanism of warm compaction: during the initial stage, the rearrangement of powder particles is the main factor which contribute more to the densification of warm compaction than to that of cold compaction; during the later stage, the plastic deformation is primary, and the improvement of plastic deformation by temperature can harmonize the second rearrangement of powder particles.With the aid of MSC.Marc 2001 Software, a numerical simulation of compaction on titanium powder has been researched. Results show that the powder movement of the convex model is more obvious than that of the level model. The former improves uniformity of density distribution.When the warm compaction combined with the convex model, the compact of titanium powder with density up to 3.87g.cm-3 can beachieved after being pressed at 500MPa. The increase in green density is 0.27g.cm"3 over conventional compaction. It is considered a new way of a lower cost to produce high performance powder metallurgy titanium alloys. |
