Abstract
High temperature tensile tests were carried out on L12 type Co3 Ti alloys, both undoped and doped with 1–4 at.-%Fe. There were anomalous increases of the 0·2% yield stress (yield strength) with increasing test temperature from 473 to 1073 K (or 1173 K, depending on the composition). The elongation and ultimate tensile stress (UTS) monotonically decreased with increasing temperature. The fracture surfaces of specimens showed a variety of fracture modes which were dependent on the test temperature and composition. There was a correlation between the ductility and the fracture mode: the more transgranular the fracture mode, the higher the ductility. It was found that Co3 Ti with 2 at.-%Fe exhibited improved ductility and it exhibited the highest peak value of yield strength and peak temperature. The alloys were also hydrogen charged to investigate their hydrogen embrittlement behaviour. Room temperature tests indicated that the addition of 2 at.-%Fe decreased the hydrogen related embrittlement.
MST/3479
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