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†

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.

Corrosion of Metallic Biomaterials: 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-based composites with ultrahigh strength and ductility achieved by equiaxing microstructure

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.

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

Biomedical TiNbZrTaSi alloys designed by d-electron alloy design theory

Polycrystalline cubic boron nitride (PCBN) and polycrystalline diamond (PCD) cutting tools were used in dry machining Ti-6Al-4V titanium alloy. Their main failure mechanisms were analyzed with a scanning electron microscope (SEM) and an energy-dispersive spectrometer (EDS). Effects of cutting parameters (cutting speed and feed rate) on tool life, cutting temperature, workpiece surface roughness, and surface microhardness were characterized with a 3-D super-depth-of-field instrument, a handheld infrared thermal imager, a surface profile measuring instrument, and a microhardness tester, respectively. The results showed that the main failure mechanisms of the PCBN tool were chipping, notch, adhesion, and crater. And, the main failure mechanisms of the PCD tool were adhesion, crater, and dissolution-diffusion. The strong diffusivity of PCD material made the performance of the PCD tool better than that of the PCBN tool. When cutting speed increased in machining with the PCD tool, decreasing cutting temperature caused by the reduction of adhered workpiece material on the tool surface resulted in a lower tool wear rate at the cutting speed of 80 m/min, and workpiece surface roughness initially increased and then decreased. The surface roughness initially increased, and after the feed rate of 0.10 mm/r, the surface roughness basically kept a constant value with feed rate increasing. High cutting speed and high feed rate increased and decreased the hardening rate of machined workpiece surface layer in machining with PCD tool, respectively.

Shengguan Qu

Papers

New Developments of Ti-Based Alloys for Biomedical Applications

Ultrafine grained Ti-based composites with ultrahigh strength and ductility achieved by equiaxing microstructure

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

Biomedical TiNbZrTaSi alloys designed by d-electron alloy design theory

Effects of cutting parameters on dry machining Ti-6Al-4V alloy with ultra-hard tools