Xiaonong Zhang

Microstructural characterization of TiB in in situ synthesized titanium matrix composites prepared by common casting technique

Abstract TiC reinforced titanium matrix composites were produced by non-consumable arc-melting technology utilizing the self-propagation high-temperature synthesis (SHS) reaction between titanium and graphite. X-Ray diffraction (XRD) was used to identify the phases in the composites. Microstructures of the composites were observed by optical microscope (OM) and transmission electron microscope (TEM). The results show that there are two phases in the composites: TiC and titanium matrix alloy. TiC has two different shapes: dendritic shape, equiaxed or near-equiaxed shape. The in situ synthesized TiC grows by dissolution–precipitation. Analysis of the binary phase diagram determined that the solidification path undertook the following three stages: primary TiC, binary eutectic β-Ti+TiC and solid transformation. Primary TiC grows in dendritic shape due to the formation of composition undercooling. Binary eutectic TiC grows in equiaxed or near-equiaxed shape. A small quantity of TiC may form twin structure during nucleation and growth. The twin plane is the (111) plane.

Hierarchical titanium surface textures affect osteoblastic functions

This study investigated the surface characteristics and in vitro cytocompatibility of hierarchical textured titanium surfaces with nanograins and microroughness, produced by surface mechanical attrition treatment (SMAT). The surface characteristics were evaluated by scanning electron microscopy, X-ray diffraction, transmission electron microscopy, contact angle, and surface energy measurements. The in vitro cytocompatibility of the SMAT processed surfaces (hereafter Ti-SMAT surfaces) were assessed in terms of cellular attachment, morphology, viability, alkaline phosphatase (ALP) activity, and mRNA gene expression. Two other titanium surfaces were compared: well-polished Ti6Al4V surfaces (hereafter Ti-polish surfaces) and thermally sprayed rough surfaces (hereafter Ti-spray surfaces). The Ti-SMAT surfaces showed a higher hydrophilicity and increased surface energy compared with the Ti-polish and Ti-spray surfaces. Consequently, these Ti-SMAT surfaces demonstrated enhancement of cell attachment, spreading, viability, and ALP activity. Reverse transcriptase polymerase chain reaction (RT-PCR) analysis showed significantly higher ALP activity and stronger expression of mRNA levels of key osteoblast genes in cells grown on the Ti-SMAT surfaces than the other two surfaces. These results reveal a synergic role played by nanostructure and microtopography in osteoblastic functions and demonstrate the more promising cytocompatibility of the hierarchical textured surfaces. It is suggested that the SMAT process may provide a novel method of surface modification to the currently available metallic biomaterials.

Oxidation behavior of in situ synthesized TiC/Ti-6Al composite

Abstract Oxidation behavior of in situ synthesized TiC/Ti–6Al composite was studied by thermal gravity analyzer (TGA). The oxidation basically followed a parabolic law and the activation energy for oxidation was calculated to be 255.7 kJ/mol. The oxidation of the composite was prior on TiC particulates because of the higher reactivity of TiC and O 2 .

Mechanical Compatability of Nanostructured Titanium with Human Bone

With their very low density, excellent biocompatibility, and good mechanochemical properties, titanium alloys have been considered a high-end material for making biomedical devices and instruments. However, they still have some substantial challenges to be overcome. One major problem, which eventually leads to revision surgery, is the implant loosening- a result of tissue migration, formation of wear debris, insufficient interface bonding between bone and implant, and stress shielding. Nanosized features in the material have the potential to provide a solution to these problems. A nanostructured surface is able to not only promote tissue ingrowth, but also increase the surface hardness and therefore improving the wear resistance and enhancing fatigue strength. This paper reports our recent work on how surface treatment on titanium alloys changes their mechanical properties. The mechanism by which the surface nanostructuring alters mechanical properties has also been discussed.

Damping behaviour of aluminium matrix composites

Abstract The damping behaviour of 6061Al/SiC/Gr and 6013Al/SiC/Gr hybrid metal matrix composites, which were fabricated by spray codeposition, was studied. From the experimental results, it was found that a damping peak at ~150°C existed in the damping spectra of these composites, no matter whether measured during heating or cooling. Through a series of analyses, it is deduced that the damping peak is of a relaxation type, and results from dislocation movement dragging defects under the coaction of heat and stress.