Titanium as an engineering material has always been limited in use by the high expense of the raw material. This expense in mostly a consequence of the large amounts of energy required to refine it.
Derek Fray, Tom Farthing and George Chen (Chen, 2000) of Cambridge University announced a new process where titanium oxide could be refined continuously, in an electrode-oxidation process producing high quality powder titanium. Estimates of the costs show that the new process should be significantly cheaper (Fray, 2001). The availability of low cost titanium powder leads to the possibility of new applications that had previously not been economically feasible.
This thesis strives firstly to press and sinter titanium powder using conventional cold pressing, investigating an optimal sintering regime and compaction pressure. The second aim is to investigate an alloy addition that should enhance sintering through the formation of a liquid phase, and is therefore a preliminary study into a potentially new set of titanium sintering alloys. The effect of silicon addition into titanium was investigated due to its suitable properties and favourable phase diagram characteristics.
Pure titanium and titanium-silicon have been successfully pressed to a suitable green density and sintered with a further increase in density. Results have shown that silicon has unusual effects on sintering both in the solid state and the liquid phase. It has been found that increasing Si content assists sintering titanium at 1200oC however is detrimental at 1350oC, even though both are solid state processes. Liquid phase sintering was achieved showing an enhanced sintering rate however an expansion event also takes place after initial sintering limiting the liquid effect on achieving a high final density.
Overall the sinterability of titanium using conventional cold pressing was successful. The addition of Si as an alloying element showed promise with improved sintering responses however further investigations are required.