| TC26 (Ti-13Nb-13Zr), as one of biomedical near-beta titanium alloys, exhibits outstanding comprehensive properties including moderate strength, high plasticity and toughness, high fatigue strength, low elastic modulus, excellent corrosion resistance and superior biocompatibility, which are applicable to surgical implants, orthodontic stents and other elastic components. TC26 is non-toxic and non-detrimental to human body so that it could be implanted into body as bio-products. This advantage has made it list into the international standard of ASTM F1713 and widely-used in global scope.Based on the exploratory investigations, the present paper has studied the evolving characteristics of microstructures and properties on hot-rolled and heat-treated TC26 plates. The finite element analysis was performed to simulate and analyze the deformation characteristics during hot-rolling. The paper also discussed the relationship between microstructural evolutions and the corresponding tensile properties as well as elastic modulus in the processing of solid-soluting and aging treatments. After a thorough master of the fundamental properties of TC26, the influential feature of hot-working technology and heat treatment on TC26 has been obtained. In addition, some technical issues on the shape-control during rolling and surface finishing of the plates were discussed, thus providing a technical support for market development and extensive production.After a hot rolling inβ-phase region, the microstructure of TC26 was typical of hot-worked structure, i.e., the obvious flow line in the longitudinal direction. The tensile strength decreased progressively with an increase in working temperature. The working hardening was pronounced in the a+P phases region, which in turn increased the strength at the expense of plasticity. That is to say, it is favorable for TC26 to improve comprehensive properties and subsequent processing when it is hot-rolled in singleβphase region.With the solid-solution temperature increasing from a+βregion toβregion, the mechanical properties of TC26 changed slightly. When TC26 was solid-soluted inβregion, the grains were growing significantly while acicular martensites were forming in the interior grain. When the alloy was solid-soluted in a+P region followed by air cooling or water quenching, the microstructures were identical as fine equiaxed P-grains, indicating a good plasticity. Consequently, the solid-solution treatment could be optimized as 700℃+0.5h, followed by air cooling or water quenching (WQ). The supercoolingβphases remained after a treatment of 800℃+0.5h/WQ, which prepared a structure for subsequent treatment of aging strengthening.Various transformations appeared upon the heating from room temperature. The hard and brittleωphases precipitated in solid-soluted matrix at a low aging temperature. With a further increase in aging temperature,ωphases increased quickly, leading to an improved strength at the expense of plasticity. Meanwhile, the elastic modulus enhanced slightly in comparison with that of solid-soluted one. The cleavage fracture morphology of aged alloys indicated a characteristic of brittle fracture. During the aging treatment of 540℃-560℃,ωphases were transforming into lash-shapedαphases completely and the microstructure consisted ofβ,α'and littleα" phases. The increasing volume fraction ofαphases resulted in a declining of strength and elastic modulus. Thus, a matching properties of strength, plasticity and low elastic modulus can be obtained at the aging temperature of 540℃-560℃. With further increasing of aging temperature to recrystallization temperature, the properties were identical to the solid-soluted alloy, indicative of an evident decrease in strength, a slight increase in plasticity and almost no change in elastic modulus. The ageing strengthening was absent in this case.In a comprehensive perspective, the optimum heat treatment is recommended as an ageing treatment of 560℃+8h after an initial solid-solution of 800℃+0.5h/WQ, so as to obtain a good matching properties of strength, plasticity and low elastic modulus as well as to prevent the precipitation ofωphases.
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