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

After almost three decades of intensive fundamental research and development activities, intermetallic titanium aluminides based on the ordered γ-TiAl phase have found applications in automotive and aircraft engine industry. The advantages of this class of innovative high-temperature materials are their low density and their good strength and creep properties up to 750 °C as well as their good oxidation and burn resistance. Advanced TiAl alloys are complex multi-phase alloys which can be processed by ingot or powder metallurgy as well as precision casting methods. Each process leads to specific microstructures which can be altered and optimized by thermo-mechanical processing and/or subsequent heat treatments. The background of these heat treatments is at least twofold, i.e., concurrent increase of ductility at room temperature and creep strength at elevated temperature. This review gives a general survey of engineering γ-TiAl based alloys, but concentrates on β-solidifying γ-TiAl based alloys which show excellent hot-workability and balanced mechanical properties when subjected to adapted heat treatments. The content of this paper comprises alloy design strategies, progress in processing, evolution of microstructure, mechanical properties as well as application-oriented aspects, but also shows how sophisticated ex situ and in situ methods can be employed to establish phase diagrams and to investigate the evolution of the micro- and nanostructure during hot-working and subsequent heat treatments.

Design, Processing, Microstructure, Properties, and Applications of Advanced Intermetallic TiAl Alloys†

Microstructurally inhomogeneous composites: Is a homogeneous reinforcement distribution optimal?

Advances in gamma titanium aluminides and their manufacturing techniques

In this article, we provide a broad and extensive review of beta titanium alloys. Beta titanium alloys are an important class of alloys that have found use in demanding applications such as aircraft structures and engines, and orthopedic and orthodontic implants. Their high strength, good corrosion resistance, excellent biocompatibility, and ease of fabrication provide significant advantages compared to other high performance alloys. The body-centered cubic (bcc) β-phase is metastable at temperatures below the beta transus temperature, providing these alloys with a wide range of microstructures and mechanical properties through processing and heat treatment. One attribute important for biomedical applications is the ability to adjust the modulus of elasticity through alloying and altering phase volume fractions. Furthermore, since these alloys are metastable, they experience stress-induced transformations in response to deformation. The attributes of these alloys make them the subject of many recent studies. In addition, researchers are pursuing development of new metastable and near-beta Ti alloys for advanced applications. In this article, we review several important topics of these alloys including phase stability, development history, thermo-mechanical processing and heat treatment, and stress-induced transformations. In addition, we address recent developments in new alloys, phase stability, superelasticity, and additive manufacturing.

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A Review of Metastable Beta Titanium Alloys

Effect of heat treatment on microstructure and mechanical properties of a new β high strength titanium alloy

Microstructure evolution and mechanical properties of a novel beta γ-TiAl alloy

Effect of aging heat treatment on microstructure and tensile properties of a new β high strength titanium alloy

In this paper, high temperature titanium matrix composites with different volume fraction of (TiB + TiC) reinforcements were in situ synthesized by casting route. The microstructure and tensile properties of the composites were presented and discussed. The results reveal that both the TiB whiskers and TiC particles tend to segregate at prior β boundaries. The prior β grain size and α lath width are gradually refined with increasing volume fraction of reinforcements. Evolution of tensile properties shows that enhancement in yield strength and ultimate tensile strength with addition of reinforcements is primarily attributed to microstructural refinement, while the remarkable reduction in ductility is possibly due to the cracking of TiB whiskers and TiC particles.

Shulong Xiao

Papers

Effect of heat treatment on microstructure and mechanical properties of a new β high strength titanium alloy

Microstructure evolution and mechanical properties of a novel beta γ-TiAl alloy

Effect of aging heat treatment on microstructure and tensile properties of a new β high strength titanium alloy

Evolution of microstructure and tensile properties of in situ titanium matrix composites with volume fraction of (TiB + TiC) reinforcements

Microstructure and fracture toughness of a β phase containing TiAl alloy