Design, and Applications Shutao Wang,†,‡ Kesong Liu, Xi Yao, and Lei Jiang*,†,‡,§ †Laboratory of Bio-inspired Smart Interface Science, Technical Institute of Physics and Chemistry, and ‡Beijing National Laboratory for Molecular Science, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, People’s Republic of China Key Laboratory of Bio-Inspired Smart Interfacial Science and Technology of Ministry of Education, School of Chemistry and Environment, BeiHang University, Beijing 100191, People’s Republic of China Department of Biomedical Sciences, City University of Hong Kong, Hong Kong P6903, People’s Republic of China

Bioinspired Surfaces with Superwettability: New Insight on Theory, Design, and Applications

Field-assisted sintering technology/Spark plasma sintering is a low voltage, direct current (DC) pulsed current activated, pressure-assisted sintering, and synthesis technique, which has been widely applied for materials processing in the recent years. After a description of its working principles and historical background, mechanical, thermal, electrical effects in FAST/SPS are presented along with the role of atmosphere. A selection of successful materials development including refractory materials, nanocrystalline functional ceramics, graded, and non-equilibrium materials is then discussed. Finally, technological aspects (advanced tool concepts, temperature measurement, finite element simulations) are covered.

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Field-Assisted Sintering Technology/Spark Plasma Sintering: Mechanisms, Materials, and Technology Developments

Review on titanium and titanium based alloys as biomaterials for orthopaedic applications.

A Review on Biomedical Titanium Alloys: Recent Progress and Prospect

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).

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

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.

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New Developments of Ti-Based Alloys for Biomedical Applications

Ultrafine-grained Ti–6Al–4V alloys were fabricated by high energy ball milling and spark plasma sintering. The effect of ball milling time and interstitial content on the microstructure and properties of sintered compacts was investigated and discussed. The sintered compacts consisted of equiaxed α+β matrixes with average grain sizes of 0.51–0.89 µm and 2–8% micrometer-sized α grains. When the ball milling time increased from 10 to 50 h, the volume fraction of coarse grains was reduced. The improvement of thermal stability may be attributed to the pinning of grain boundaries by nanostructured TiO 2 particles and solute drag of interstitial atoms. The sintered compacts with ultrafine-grained structures exhibited 80–120% higher compressive yield strength than that of the coarse-grained alloy. The contributions of grain refinement strengthening and solid-solution/oxide dispersion strengthening via interstitial elements were evaluated by a modified Hall–Petch equation: σ cy =393+0.46 d −1/2 +519 O eq 1/2 . When the ball milling time was 10 h, a balance of high strength (compressive yield strength=1260 MPa, ultimate compressive strength=1663 MPa) and sufficient plasticity (plastic strain to failure=20%) could be achieved.

High-strength Ti–6Al–4V with ultrafine-grained structure fabricated by high energy ball milling and spark plasma sintering

The as-cast AZ91 plate was subjected to normal friction stir processing (processed in air) and submerged friction stir processing (processed in water, SFSP), and microstructure and superplastic tensile behavior of the experimental alloys were investigated. SFSP results in remarkable grain refinement due to the enhanced cooling rate compared with normal FSP, with an average grain size of 1.2 μm and 7.8 μm. The SFSP AZ91 specimen exhibits considerably enhanced superplastic ductility with reduced flow stress and higher optimum strain rate, as compared to the normal FSP specimen. The optimum superplastic deformation temperature is found to be 623 K for both the normal FSP and SFSP AZ91 specimens. An elongation of 990% is obtained at 2×10−2 s−1 and 623 K for the SFSP specimen, indicating that excellent high strain rate superplasticity could be achieved. By comparison, maximum ductility of the normal FSP specimen strained at high strain rate is 158%. Grain boundary sliding is the main mechanism for the superplastic deformation of the normal FSP and SFSP specimens. The excellent high strain rate superplasticity of the SFSP alloy is attributed to its finer grain structure and higher fraction of grain boundary.

High strain rate superplasticity of a fine-grained AZ91 magnesium alloy prepared by submerged friction stir processing

Mechanical and corrosion properties of Mg-Gd-Zn-Zr-Mn biodegradable alloy by hot extrusion

Blended 93W–5.6Ni–1.4Fe powders were sintered via the spark plasma sintering (SPS) technique. Fine-grained 93W–5.6Ni–1.4Fe heavy alloys (W grain size is about 6 µm) with liquid-phase sintered microstructure were obtained by control of the SPS process. After SPS, the alloys show relative density of 0.95 and tungsten–tungsten contiguity of 0.53. The alloys exhibit improved bending strength (about 1580 MPa) and yield strength (about 1050 MPa at room temperature and about 640 MPa at 800 °C), due to their fine-grained structure. The fracture morphology after bending test is mainly characterized as tungsten–tungsten intergranular rupture. A decreased tungsten–matrix interface decohesion is presented due to the improved binding strength of tungsten–matrix by “SPS effect”. The mechanical properties of SPSed 93W–5.6Ni–1.4Fe heavy alloys are dependent on the microstructural parameters such as tungsten grain size, matrix volume fraction and tungsten–tungsten contiguity.

Yuanyuan Li

Papers

New Developments of Ti-Based Alloys for Biomedical Applications

High-strength Ti–6Al–4V with ultrafine-grained structure fabricated by high energy ball milling and spark plasma sintering

High strain rate superplasticity of a fine-grained AZ91 magnesium alloy prepared by submerged friction stir processing

Mechanical and corrosion properties of Mg-Gd-Zn-Zr-Mn biodegradable alloy by hot extrusion

Fine-grained 93W-5.6Ni-1.4Fe heavy alloys with enhanced performance prepared by spark plasma sintering