Powder Metallurgy Titanium And Porous Titanium Research

Titanium is the most significant material for replacement material because of poison less, high specific strength, superior bio-compatibility and lower Yang's modulus approaching bone. Powder metallurgy (PM) technology is one of the near-net shape technologies to fabricate titanium alloy part with low production cost, which has been carried out in abroad for its low cutting ratio.In this article, the sintering of PM pure titanium from hydrogenation-dehydrogenation (HDH) Ti powder, the influence of Nd on PM pure titanium and the preparation of porous titanium were seriously investigated. A large amount of experimental and theoretical analyses were conducted by optical microscopy, scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDXA) and Elementary analysis.The process of making PM pure titanium using HDH titanium powder was studied. During the process of sintering, high properties were obtained in the high vacuum of 10 Pa with the temperature of 1100°C for 2h. The relative density and average grain size of the sintered part is 95.56% and 30μm respectively. Tensile strength of the sintered part is about 770MPa, and the elongation percentage is no more than 1%, which present brittle fracture. On the contary, the tensile strength of high purity titanium sheet is about 334MPa, and the elongation exceeds 60%, which present ductility fracture. It is found that the carbon content and oxygen content of the sintered part is about 0.080wt.% and 0.38wt.% respectively, and the carbon content and oxygen content of high purity titanium sheet is about 0.080wt.% and 0.075wt.% respectively. The deformation ability is deteriorated for much higher carbon content and oxygen content of the sintered part.With the addition of Nd powder, PM Ti-0.8wt.%Nd with the average grain size of about 20μm were obtained in the high vacuum of 10 Pa with the temperature of 1100°C for 2h, the average grain size of which is significantly refined. With the increasing of Nd content, yield deformation is present in PM Ti-xNd. Superior properties of PM Ti-4.0wt.%Nd is obtained with the yield strength, tensile strength and elongation of about 630MPa, 700MPa and 7.5% respectively. It is significant for further investigation on improving the plastic deformation ability of PM titanium.With the addition of TiH₂ powder in HDH Ti powder, porous titanium with the open porosity of about 20% was obtained in vacuum dehydrogenation-sintering of 10 Pa with the temperature of 1100°C for 2h. With the addition of PW as binder, porous titanium with the open porosity of about 30% was obtained based on the same mixture ratio of TiH₂ powder and HDH Ti powder in vacuum dehydrogenation-sintering of 10^-3 Pa with the temperature of 1100°C for 2h. Using HDH Ti powder with the particle size distribution of+300～-200mesh, porous in the shape of hollow is present in porous titanium material and the pore-forming mechanism is mainly the pore reservation mechanism of thick powder. Using HDH Ti powder with the particle size distribution of -500mesh, porous in the shape of thin tube is present, the pore-forming mechanism is mainly the mechanism of the dehydrogenation of TiH₂ powder in wrapped particle under high temperature in vacuum, which is formed by the wrapping of HDH Ti powder with finer particle size on the surface of TiH₂ powder during near normal atmosphere sintering. It is significant for further preparation of replacement material with compact core and porous external layer by co-injection molding, simultaneously debinding and sintering.