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Bulk ultrafine structured metallic materials with the bi-modal grain size distribution exhibit both high strength and good ductility. Here we show a new family of bi-modal Ti-Nb-Ni-Co-Al alloys. Their microstructure consists of an ultrafine structured eutectic matrix and relatively coarse β-Ti dendrites. Chemical modification of the parent Ti-Nb-Ni-Cu-Al system significantly affected type and volume fraction of matrix phases. In its turn, this influenced the deformation behavior. The unexpected "double yielding" behavior as well as tensile/compressive fracture strength asymmetry of the designed alloys are discussed in detail. For that, the microstructure alterations under compressive and tensile loading was in situ and ex situ analyzed by scanning electron microscopy. [ABSTRACT FROM AUTHOR]

Tensile ductility of the Ti-based composites, which consist of a β-Ti phase surrounded by ultrafine structured intermetallics, is tunable through the control of intermetallics. The two Ti-based alloys studied exhibit similar compressive yield strength (about 1000MPa) and strain (about 35%-40%) but show a distinct difference in their tensile plasticity. The alloy Ti71.8Nb14.1Ni7.4Al6.7 fractures at the yield stress while the alloy Ti71.8Nb14.1Co7.4Al6.7 exhibits about 4.5% of tensile plastic deformation. To clarify the effect of microstructure on the deformation behavior of these alloys, tensile tests were carried out in the scanning electron microscope. It is shown that the distribution as well as the type of intermetallics affects the tensile ductility of the alloys. [ABSTRACT FROM AUTHOR]

The close match of stiffness between implant material and bone is critically important to avoid stress-shielding effect and ensure a fast healing of injured tissues. Here, we introduce liquid metal dealloying method for synthesis of robust open porous biomaterials possessing low Young's modulus. The remarkable advantage of the liquid metal dealloying method is a large flexibility in selecting chemical composition of a desired porous biomaterial together with unique tunable microstructure. To demonstrate the versatility of the method, a number of open porous Ti x Zr 100-x alloys with different chemical compositions and microstructural characteristics was developed by dealloying precursor (Ti x Zr 100-x ) y Cu 100-y alloys in liquid magnesium. The effects of the processing conditions and the precursors' chemical composition on the microstructure of the porous Ti x Zr 100-x as well as their mechanical behavior were discussed in detail. In particular, the porous Ti x Zr 100-x distinguish themselves due to a low and tunable stiffness ranging from 3.2 to 15.1 GPa and a rather high strength reaching up to 480 MPa. This unique combination of mechanical properties of the new open porous Ti x Zr 100-x alloys becomes even more interesting in view of preliminary biological tests highlighting their excellent cytocompatibility. Overall, the liquid metal dealloying provides an opportunity for designing a new biomaterials platform with flexible tunable functionality., (Copyright © 2018 Elsevier B.V. All rights reserved.)

The long-term performance of orthopedic implants depends crucially on a close match between the mechanical behavior of bone and of the implant material. Yet, the present man-made materials with the required biocompatibility and strength are substantially stiffer than bone. This mismatch results in stress shielding, which can lead to the loss of bone mass and may even lead to a revision surgery. Here we report a new materials design strategy towards metal-polymer composites that are based on constituents with established biocompatibility and that can be matched to bone. Ti-based nanoporous alloys, prepared by liquid-metal dealloying, are infiltrated with epoxy to form interpenetrating-phase nanocomposites. At up to 260 MPa, their yield strength is technologically interesting for a deformable light-weight material. More importantly, Young's modulus can be adjusted between 4.4 and 24 GPa, which affords matching to bone. As another parallel to bone, the strength of the composite materials is strain-rate dependent. These findings suggest that the novel composite materials may provide the basis for promising future implant materials.

The effect of chemical composition on microstructure and tensile properties of a series of low modulus Ti-Nb-Cu-Ni-Al alloys was studied. These alloys consist of primary micrometer-sized β-Ti dendrites surrounded by intermetallic phases. The morphology of the intermetallic phases is strongly affected by composition. Due to the composite microstructure, the alloys exhibit a low Young's modulus (77-84GPa) together with a high yield strength of about 1000MPa as well as moderate tensile ductility. The results demonstrate that complete substitution of Al by Ti reduces the Young's modulus by 5%. Increasing Nb content at the expense of Ti causes a significant improvement of tensile ductility., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

The correlation between the microstructure and mechanical behavior during tensile loading of Ti68.8Nb13.6Al6.5Cu6Ni5.1 and Ti71.8Nb14.1Al6.7Cu4Ni3.4 alloys was investigated. The present alloys were prepared by the non-equilibrium processing applying relatively high cooling rates. The microstructure consists of a dendritic bcc β-Ti solid solution and fine intermetallic precipitates in the interdendritic region. The volume fraction of the intermetallic phases decreases significantly with slightly decreasing the Cu and Ni content. Consequently, the fracture mechanism in tension changes from cleavage to shear. This in turn strongly enhances the ductility of the alloy and as a result Ti71.8Nb14.1Al6.7Cu4Ni3.4 demonstrates a significant tensile ductility of about 14% combined with the high yield strength of above 820 MPa already in the as-cast state. The results demonstrate that the control of precipitates can significantly enhance the ductility and yet maintaining the high strength and the low Young's modulus of these alloys. The achieved high bio performance (ratio of strength to Young's modulus) is comparable (or even superior) with that of the recently developed Ti-based biomedical alloys., (© 2013.)