Fatigue Behaviour of Additive Manufactured Ti-TiB

Fatigue behaviour of titanium reinforced with TiB particles fabricated by ‘plasma transferred arc solid freeform fabrication’ (PTA-SFFF) technique was investigated. Rotation bending fatigue tests were conducted following the MPIF 56 standard using the staircase method approach. Experimental data is used to calculate the fatigue strength and construct S-N curves, where the results were compared to a powder metallurgy FC0205 as a benchmark material. The titanium samples were found to exhibit superior fatigue behaviour in comparison to the reference FC0205 material, performing well above 1/3 of its ultimate tensile strength with a 90% survival fatigue strength of 244 +/- 98.3 MPa versus 141 +/- 17.4 MPa. Fatigue failure mechanisms of samples were identified by examination of the fracture surfaces through scanning electron microscopy (SEM) as well as using transmission-electron microscopy (TEM) and focused ion beam (FIB) analysis techniques. Fatigue crack propagation was either arrested or deflected when propagation occurred within the vicinity of the TiB intermetallics. Fracture surfaces of the titanium matrix displayed evidence of striations while the TiB intermetallic experience cleavage fracture.