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Tungsten fiber reinforced tungsten (W f /W) composite is one of the candidates to improve the toughness of tungsten materials. Powder metallurgy is a potential method to produce W f /W composites, but it may cause the recrystallization and grain growth of the reinforcing fibers during the high temperature sintering process. In the present work, a layer of Y 2 O 3 is coated on the fiber surface by magnetron sputtering to protect the fibers and prevent recrystallization and abnormal growth of grains. W f /W composites with and without Y 2 O 3 coating were fabricated by a field assisted sintering technology (FAST) process. Microstructure and mechanical properties were characterized. The influence of the Y 2 O 3 coating on the properties of the fiber was discussed in detail. The Y 2 O 3 coating can effectively prevent recrystallization and abnormal grain growth of fibers during the sintering process. The W f /W composites with Y 2 O 3 coating shows higher strength and pseudo-ductile behavior. • Continuous fiber reinforced W f /W composites are fabricated via PM. • Y 2 O 3 coating can prevent recrystallization and abnormal grain growth of fibers during the sintering process. • The improvement of the toughness is mainly contributed by the high strength of the fiber. [ABSTRACT FROM AUTHOR]

Abstract The W/Ti multilayer composites are prepared by spark plasma sintering. The original constituents are cold-rolled W foils with elongated grains and annealed Ti-1.5Al foils with fine equiaxed grains. After diffusion bonding, both elongated grains and fine equiaxed grains can be seen in the W layers. The diffusion rate of W in Ti is much faster than that of Ti in W due to different methods of diffusion. The detailed microstructure of W/Ti laminates can be divided into four types at different regions including pure W, mixture of α-W and β-Ti with light and dark lamellas, pure β-Ti and Ti-rich Widmanstäten α-β structure with alternative light and dark lamellas. Compared with the microhardness of original materials, the microhardness of W layers slightly decreases and the microhardness of Ti layers increases dramatically. Highlights • W/Ti multilayer composites are prepared by spark plasma sintering. • The detailed microstructure of W/Ti laminates can be divided into four layers. • The formation mechanism of the microstructure is determined. • The strengthening mechanism in the Ti layer is proposed. [ABSTRACT FROM AUTHOR]

The characteristics of shear bands in cold-rolled Ta-2.5W alloy are systematically investigated at different mechanical reduction levels. With increasing strain, the shear bands can appear as in-grain shear bands, trans-granular shear bands and wavy bands. At low strain the crystallographic planar in-grain shear bands are aligned close to the highly stressed slip planes at low strain. As strain increases, the shear bands rotate around the <110> or <111> direction to smaller inclination angles with respect to the rolling direction (RD). Meanwhile, new groups of shear bands are developed. Two groups of in-grain shear bands with a specific fishbone structure appear in the orientations with larger Taylor factor at medium strain. The trans-granular shear bands are formed when the adjacent grains get the continuity of slip planes. Therefore, the frequency of trans-granular shear bands increases with the enhancing of local texture. The wavy bands appear to be a result of sequential necking in the harder γ-fiber and a cooperative flow in the softer α-fiber. Meanwhile, the formation model of the wavy bands is also proposed based on the laminar composites. [ABSTRACT FROM AUTHOR]