Abstract
In this study fatigue and tensile test specimens were produced by Metal Injection Moulding (MIM) using gas atomised Ti-6Al-4V-powder with addition of 0.5 wt.% yttrium powder as well as pure Ti‑6Al‑4V‑powder as reference. The addition of yttrium resulted in a noticeably refinement of the grain size from 150 µm to 50 µm by formation of Y2O3 particles hindering grain growth. Corresponding scavenging of oxygen from the titanium matrix led to a decrease in tensile strength of about 70 MPa. Surprisingly, fatigue strength was enhanced by 15 to 60 MPa, probably caused by the colony refinement overcompensating the effect of decreased yield strength. To understand the formation kinetics of Y2O3, in situ X-ray diffraction experiments were performed during sintering using synchrotron radiation. The results show that only a small amount of yttrium was dissolved while the remainder was oxidized. The formation of Y2O3 took place between 850 and 1050 °C.
