Progress in research on hybrid metal matrix composites

In-situ TiC/Ti titanium matrix composites were successfully fabricated through a novel approach, utilizing the reaction of graphene and Ti mixture powders in spark plasma sintering. Microstructure, hardness and compressive properties of such composites were investigated. The layered graphene nanosheets as the carbon source were dispersed in the powders, and subsequently formed uniform TiC particles in Ti matrix during the rapid sintering. The resulting TiC particles exhibited the micro- and nano-sized equiaxial structures. Such composites possessed the significantly enhanced hardness and room-temperature compressive strength comparing with the as-cast and as-sintered pure Ti. The ultimate and yield compressive strengths of as-prepared 7.0 vol% TiC incorporated composite respectively reached up to 2.64 GPa and 1.93 GPa, beyond some advanced Ti materials reported to date. In-situ micro- and nano-sized TiC particles were believed to be beneficial to harden and strengthen Ti matrix. The relevant strengthening mechanisms of such composites were discussed.

Microstructural and mechanical characterization of in-situ TiC/Ti titanium matrix composites fabricated by graphene/Ti sintering reaction

Selective laser melting enabled additive manufacturing of Ti–22Al–25Nb intermetallic: Excellent combination of strength and ductility, and unique microstructural features associated

Recrystallization mechanisms and microstructure development in emerging metallic materials: A review

3D processing map and hot deformation behavior of 6A02 aluminum alloy

In this study, the microstructural evolution and mechanical properties of a newly near α titanium alloy with trace additions of B by in situ casting route are investigated. The results show that the coarse prior β grain and α lath within matrix alloy are gradually refined with increasing of B addition. The relative refinement mechanism of prior β grain and α lath width is analyzed and discussed. In addition, it is shown that both of ultimate compressive strength (UCS) and yield strength (UYS) increase with B addition, which is mainly attributed to microstructural refinement. However, the compressive ductility and fracture toughness decrease with increasing of B addition, which is due to the cracking of TiB, leading to the acceleration of crack extension.

Effect of Trace B on the Microstructure and Mechanical Properties of a Newly Near α High Temperature Titanium Alloy

The microstructure and cellular transition characteristics of an intermetallic Ti-42Al-3Nb-1Mo-0.1B (at.%) alloy were investigated. The as-cast microstructure of the alloy is mainly composed of (α2+γ) lamellar structure and (β+γ) mixture structure, which distributes along the boundaries of the lamellar colonies. In order to study the phase transformation of lamellar structure at aging temperature, a two-step heat treatment was carried out. After the first step of annealing treatment at 1,260 °C, the microstructure with relatively finer lamellar space and (γ+β/B2) mixture structure is obtained. Aging treatment, as the second heat treatment step, has significant influence on the microstructure, attributing to a cellular reaction of α2+γ→ γ+β. With the increase of aging temperature, the (α2+γ) lamellar structure continues to dissolve, whereas the contents of both the equiaxed γ and β/B2 grains continuously increase. Besides, the orientation of lamellae α2, equiaxed γ and equiaxed β/B2 in the cellular transition region follows a specific relationship of {0–11}β β//{0001}α2 α2//{1–11}γ γ.

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Microstructure and cellular transition characteristic of Ti-42Al-3Nb-1Mo-0.1B alloy

In this study, a Ti composite reinforced with 5 vol. % (TiBw + TiCp) was fabricated by an in situ casting route. Open die forging in (α + β) phase region was conducted on the composite casting. The microstructures of the as-forged composite pancake are inhomogeneous in terms of matrix microstructure and distribution of reinforcements. The matrix grains are gradually refined from the periphery to centre of the pancake. The reinforcements TiBw and TiCp tend to be uniformly distributed in the centre region. It is suggested that the microstructure difference can be mainly ascribed to the temperature variation from the periphery to the centre. The tensile testing results show that the centre region of the composite pancake exhibits higher strength than the peripheral region. The mechanical behaviour of the composite pancake with the temperature is discussed.

The Microstructural Characterization and Mechanical Properties of 5 vol. % (TiBw + TiCp)/Ti Composite Produced by Open-Die Forging

Hot Deformation Behavior and Microstructure Evolution of a New Near β Titanium Alloy Reinforced with Trace TiCp

In this study, the cold rolling microstructure and static recrystallization mechanism of the high strength titanium alloy Ti-3.5Al-5Mo-6V-3Cr-2Sn-0.5Fe were systematically investigated. Results show that the cold rolling microstructure is mainly composed of the elongated deformed β grains containing micro-shear bands. After annealing at 815 °C for 2 min, the fine SRXed grains are observed, mainly concentrated in the micro-shear band, the grain boundary and the interior of the deformed grain. The sub-grain structure obtained by static recovery inside the deformed grain produces continuous SRX during the annealing treatment. Meanwhile, geometric and discontinued SRXed grains are also observed in the large deformed β grain and at the trigeminal grain boundaries, respectively. Many ultra-fine grains appear inside the micro-shear band, exhibiting a phenomenon of the micro-shear band assisting SRX. With the increase in the annealing holding time, the elongated β grains are significantly refined and the degree of recrystallization is continuously improved. In addition, the recrystallization behavior also results in a significant change in the fiber texture. With the extension of the annealing holding time, the rolling texture type evolves gradually, with the {111} <112> γ-fiber texture to weak α-fiber, γ-fiber, and Goss-fiber.

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Shuzhi Zhang

Papers

Effect of Trace B on the Microstructure and Mechanical Properties of a Newly Near α High Temperature Titanium Alloy

Microstructure and cellular transition characteristic of Ti-42Al-3Nb-1Mo-0.1B alloy

The Microstructural Characterization and Mechanical Properties of 5 vol. % (TiBw + TiCp)/Ti Composite Produced by Open-Die Forging

Hot Deformation Behavior and Microstructure Evolution of a New Near β Titanium Alloy Reinforced with Trace TiCp

Static Recrystallization Behavior and Texture Evolution during Annealing in a Cold Rolling Beta Titanium Alloy Sheet