| Solution heat treatment and more complex thermomechanical treatments were performed on the recently developed two near-α Ti alloys, Ti-1100 and IMI 834. Equiaxed, bimodal and β-transformed lamellar α+βmicrostructures were provided with both alloys. This study was intended to obtain the optimum mechanical properties and to rank these alloys. To investigate the mechanical properties of these alloys, tensile tests were conducted at temperatures ranging from room temperature to 700℃. High cycle fatigue(HCF) tests were performed at room temperature and at 400℃. Creep tests were done at 600℃. Test results exhibited that all the mechanical properties of the IMI 834 were slightly superior to those of the Ti-1100. Creep strength of the bimodal microstructure was always about 50MPa lower than that of the lamellar structure up to 700℃. Considering overall properties, however, the bimodal microstructure produced by a thermomechanical treatment done just below the Q-transus temperatures exhibited the most optimum properties. The thermomechanical treatments change the microstructures and consequently influence the mechanical properties. This process can be used to meet the special requirements for either room-or high-temperature applications. |
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