The Influence of Severe Plastic Deformation on Microstructure and In Vitro Biocompatibility of the New Ti-Nb-Zr-Ta-Fe-O Alloy Composition

Abstract

In this work, severe plastic deformation (SPD) of the newly designed Ti-Nb-Zr-Ta-Fe-O GUM metal was successfully conducted at room temperature using high speed high pressure torsion (HSHPT) followed by cold rolling (CR) to exploit the suitability of the processed alloy for bone staples. The Ti-31.5Nb-3.1Zr-3.1Ta-0.9Fe-0.16O GUM alloy was fabricated in a levitation melting furnace using a cold crucible and argon protective atmosphere. The as-cast specimens were subjected to SPD, specifically HSHPT, and then processed by the CR method to take the advantages of both grain refinement and larger dimensions. This approach creates the opportunity to obtain temporary orthopedic implants nanostructured by SPD. The changes induced by HSHPT technology from the coarse dendrite directly into the ultrafine grained structure were examined by optical microscopy, scanning electron microscopy and X-ray diffraction. The structural investigations showed that by increasing the deformation, a high density of grain boundaries is accumulated, leading gradually to fine grain size. In addition, the in vitro biocompatibility studies were conducted in parallel on the GUM alloy specimens in the as-cast state, and after HSHPT- and HSHPT+CR- processing. For comparative purposes, in vitro behavior of the bone-derived MC3T3-E1 cells on the commercially pure titanium has also been investigated regarding the viability and proliferation, morphology and osteogenic differentiation. The results obtained support the appropriateness of the HSHPT technology for developing compression staples able to ensure a better fixation of bone fragments.

Evolution of Microstructural and Mechanical Properties during Cold-Rolling Deformation of a Biocompatible Ti-Nb-Zr-Ta Alloy

“…It can be also remarked that deformation bands and twins become more and more visible as the intensity of cold-rolling deformation increases. Similar observations were obtained in the case of different types of Ti alloys [ 57 , 58 , 59 , 60 , 61 , 62 , 63 , 64 , 65 , 66 ]. The most obvious microstructural features induced by the intense deformation are shown in Figure 3 d, which illustrates the microstructure of the TNZT alloy when subjected to a 60% deformation degree.…”

Effects of Cold Rolling Deformation and Solution Treatment on Microstructural, Mechanical, and Corrosion Properties of a Biocompatible Ti-Nb-Ta-Zr Alloy

“…Depending on the processing route, containing both cold-deformation and thermal treatments, the elastic modulus of TNTZ or other similar alloys (TZN, TNZ) was drastically influenced [36][37][38][39][40][41][42][43][44]. If phase changes occur during cold-deformation and/or thermal treatments, the β-Ti/α"-Ti phase proportion and characteristics are strongly influenced as-well [38].…”

Using a two-step method of surface mechanical attrition treatment and calcium ion implantation to promote the osteogenic activity of mesenchymal stem cells as well as biomineralization on a β-titanium surface

“…Aside from the elastic modulus, limited osseointegration of the implant and bone is another issue that hinders the broader application of Ti-based alloy in the clinic. 4,5,31 It has been acknowledged that refining grains by means of equal channel angular pressing (ECAP) 56,57 and high-pressure torsion (HPT) 58,59 could improve cell–material interactions, thus boosting the osseointegration of Ti-based alloys. However, the elastic modulus is also elevated after these bulk-nanostructuring treatments, which in turn aggravates the mismatch in the moduli of the implant and bone.…”