Yuhua Li

Bio: Yuhua Li is an academic researcher from South China University of Technology. The author has contributed to research in topics: Sintering & Amorphous metal. The author has an hindex of 5, co-authored 7 publications receiving 560 citations.

New Developments of Ti-Based Alloys for Biomedical Applications

Abstract: Ti-based alloys are finding ever-increasing applications in biomaterials due to their excellent mechanical, physical and biological performance. Nowdays, low modulus β-type Ti-based alloys are still being developed. Meanwhile, porous Ti-based alloys are being developed as an alternative orthopedic implant material, as they can provide good biological fixation through bone tissue ingrowth into the porous network. This paper focuses on recent developments of biomedical Ti-based alloys. It can be divided into four main sections. The first section focuses on the fundamental requirements titanium biomaterial should fulfill and its market and application prospects. This section is followed by discussing basic phases, alloying elements and mechanical properties of low modulus β-type Ti-based alloys. Thermal treatment, grain size, texture and properties in Ti-based alloys and their limitations are dicussed in the third section. Finally, the fourth section reviews the influence of microstructural configurations on mechanical properties of porous Ti-based alloys and all known methods for fabricating porous Ti-based alloys. This section also reviews prospects and challenges of porous Ti-based alloys, emphasizing their current status, future opportunities and obstacles for expanded applications. Overall, efforts have been made to reveal the latest scenario of bulk and porous Ti-based materials for biomedical applications.

High-strength low-modulus medical ultra-fine grain titanium matrix composite and preparation method thereof

Abstract: The invention relates to a high-strength low-modulus medical ultra-fine grain titanium matrix composite and a preparation method thereof. In the microstructure of the composite prepared by the method, beta-Ti is a matrix phase, and FeTi is reinforcing phase; the preparation method of the composite is a forming method combining a pulse current sintering technology and an amorphous crystallization method and comprises the following steps of: mixing powder and carrying out high-energy ball milling till alloy powder has a wide an undercooling liquid phase region and the volume of an amorphous phase accounts for at least 80% of the total volume; and then carrying out rapid sintering by adopting a discharge plasma sintering system, wherein the sintering temperature (Ts) is greater than or equal to the crystallization temperature of the amorphous alloy powder, the Ts is less than or equal to the fusion temperature of the amorphous alloy powder, the sintering pressure is 40-80MPa, and the heating rate is 50-200DEG/min. The preparation method has the advantages of simpleness, high finished product yield and near net shape; and the formed composite has the advantages of larger size, clear internal interface, controlled grain size, good biocompatibility, excellent comprehensive mechanical property and good popularization and application prospect.

Microstructure evolution and thermal properties in FeMoPCB alloy during mechanical alloying

Abstract: Fe79.3Mo4.5P8.1C6.75B1.35 amorphous alloy composite powder from respective element powders of Fe, Mo, C, B, and Fe–P intermediate compound, was synthesized by mechanical alloying. Microstructure evolution analysis indicates that the synthesized amorphous alloy composite powder after a milling time of 70 h encompasses predominately amorphous matrix embedded by nanocrystalline α-Fe with a grain size of about 5.5 nm. However, unlike other Fe-based amorphous alloys, the synthesized amorphous alloy composite powder exhibits no obvious supercooled liquid region with only crystallization temperature. The corresponding crystallization onset temperature and exothermic enthalpy measured from DSC curves are about 762 K and 15.86 J/g, respectively. The results obtained provide good candidate materials for fabricating bulk metallic glass composites and related bulk nanocrystalline materials.

Medical ultra-fine grain titanium alloy with ultrahigh plasticity, high strength and low modulus and preparation method thereof

Abstract: The invention discloses a medical ultra-fine grain titanium alloy with ultrahigh plasticity, high strength and low modulus and a preparation method thereof. The medical ultra-fine grain titanium alloy contains the following specific components in atomic percent: 60-70% of Ti, 16-24% of Nb, 5-14% of Zr, 1-8% of Ta, 0-5% of Si, and inevitable trace impurities. The preparation method of the medical ultra-fine grain titanium alloy is a formation method of the powder metallurgy sintering technology combined with an amorphous crystallization method; specifically, powder mixing and high-energy ball milling are performed until the content of the amorphous phase is maximum, next, the powder metallurgy sintering technology is adopted to solidify the alloy powder, and finally, a spark plasma sintering system or a vacuum hot pressing furnace is adopted for sintering by use of pulse current or radiation heating. The prepared complex-structure medical ultra-fine grain titanium alloy with ultrahigh plasticity, high strength and low modulus is good in biocompatibility, controllable in grain size, excellent in comprehensive mechanical properties and bright popularization and application prospect.

Ti-based high temperature alloy with high toughness in bi-state structure and preparation method and application thereof

Abstract: The invention belongs to the technical field of metal high temperature alloys, and discloses a ti-based high temperature alloy with high toughness in a bi-state structure and a preparation method and an application thereof. The high temperature alloy comprises the following components in atomic percent: 64-68at.% of Ti, 8-18at.% of Nb, 6-10at.% of Cu, 5-8at.% of Ni, 3-8at.% of Al and inevitable trace impurities. The structure of the ti-based high temperature alloy consists of a widmanstatten structural base body and an equiaxial (Cu, Ni)-Ti2 phase. The invention further discloses the preparation method of the ti-based high temperature alloy. The method comprises the following steps: first, preparing alloy powder by high energy milling; and then, quickly sintering alloy powder by pulse current, wherein the process condition is as follows: in a spark plasma sintering system of pulse current, sintering is carried out for 5-25 minutes at the sintering temperature of 800-1000 DEG C and the sintering pressure of 30-400MPa, and therefor the ti-based high temperature alloy with high toughness in the bi-state structure is obtained.

Selective Laser Melting of Titanium Alloys and Titanium Matrix Composites for Biomedical Applications: A Review†

Abstract: Titanium materials are ideal targets for selective laser melting (SLM), because they are expensive and difficult to machinery using traditional technologies. After briefly introducing the SLM process and processing factors involved, this paper reviews the recent progresses in SLM of titanium alloys and their composites for biomedical applications, especially developing new titanium powder for SLM. Although the current feedstock titanium powder for SLM is limited to CP-Ti, Ti–6Al–4V, and Ti–6Al–7Nb, this review extends attractive progresses in the SLM of all types of titanium, composites, and porous structures including Ti–24Nb–4Zr–8Sn and Ti–TiB/TiC composites with focus on the manufacture by SLM and resulting unique microstructure and properties (mechanical, wear/corrosion resistance properties).

Corrosion of Metallic Biomaterials: A Review

Abstract: Metallic biomaterials are used in medical devices in humans more than any other family of materials. The corrosion resistance of an implant material affects its functionality and durability and is a prime factor governing biocompatibility. The fundamental paradigm of metallic biomaterials, except biodegradable metals, has been “the more corrosion resistant, the more biocompatible.” The body environment is harsh and raises several challenges with respect to corrosion control. In this invited review paper, the body environment is analysed in detail and the possible effects of the corrosion of different biomaterials on biocompatibility are discussed. Then, the kinetics of corrosion, passivity, its breakdown and regeneration in vivo are conferred. Next, the mostly used metallic biomaterials and their corrosion performance are reviewed. These biomaterials include stainless steels, cobalt-chromium alloys, titanium and its alloys, Nitinol shape memory alloy, dental amalgams, gold, metallic glasses and biodegradable metals. Then, the principles of implant failure, retrieval and failure analysis are highlighted, followed by description of the most common corrosion processes in vivo. Finally, approaches to control the corrosion of metallic biomaterials are highlighted.

Titanium nanostructures for biomedical applications

Abstract: Titanium and titanium alloys exhibit a unique combination of strength and biocompatibility, which enables their use in medical applications and accounts for their extensive use as implant materials in the last 50 years. Currently, a large amount of research is being carried out in order to determine the optimal surface topography for use in bioapplications, and thus the emphasis is on nanotechnology for biomedical applications. It was recently shown that titanium implants with rough surface topography and free energy increase osteoblast adhesion, maturation and subsequent bone formation. Furthermore, the adhesion of different cell lines to the surface of titanium implants is influenced by the surface characteristics of titanium; namely topography, charge distribution and chemistry. The present review article focuses on the specific nanotopography of titanium, i.e. titanium dioxide (TiO2) nanotubes, using a simple electrochemical anodisation method of the metallic substrate and other processes such as the hydrothermal or sol-gel template. One key advantage of using TiO2 nanotubes in cell interactions is based on the fact that TiO2 nanotube morphology is correlated with cell adhesion, spreading, growth and differentiation of mesenchymal stem cells, which were shown to be maximally induced on smaller diameter nanotubes (15 nm), but hindered on larger diameter (100 nm) tubes, leading to cell death and apoptosis. Research has supported the significance of nanotopography (TiO2 nanotube diameter) in cell adhesion and cell growth, and suggests that the mechanics of focal adhesion formation are similar among different cell types. As such, the present review will focus on perhaps the most spectacular and surprising one-dimensional structures and their unique biomedical applications for increased osseointegration, protein interaction and antibacterial properties.