EFFECT OF ALLOYING ADDITIONS OF ALUMINIUM AND IRON ON THE CREEP RESISTANCE OF TI-12CR (WT.%)

Aging certain metastable beta titanium (β-Ti) alloys between 373 K to 773 K allows for phase transformations to occur from beta (β) to omega (ω) and from beta (β) to alpha (α). Both omega (ω) and alpha (α) phases exhibit enhanced strengths and hardness values [1]. Future research is focused at achieving comparable mechanical properties with cheaper ferro-chrome substitutes to the commercially used Ti-alloys [2]. β-Ti alloys with the ω-phase usually tend to exhibit higher strengths and hardness values than the ones that do not contain the ω-phase [3].

In this study, the creep properties of three different β-Ti alloys, Ti-12Cr-1Fe-3Al (wt. %), Ti-12Cr-3Al (wt.%), and T-12Cr (wt. %), were experimentally measured at a temperature of 683K and applied stresses between 200-350 MPa. The relationship between microstructure and creep properties were investigated. X-ray diffractometer (XRD), optical microscope (OM), and scanning electron microscope (SEM) were used to characterize the microstructure before and after creep deformation. The hardness of the alloys increased after heat treatment for 48 hrs at 683 K due to the precipitation of α and/or ω phases. The creep tests showed that Ti-12Cr-1Fe-3Al (wt. %) was the most creep resistant and Ti-12Cr (wt. %) was the least creep resistant.