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Highlights: [•] Glycine doped MgB2 can be made at low temperature by Cu-activated sintering. [•] We obtained excellent J c in glycine-doped MgB2 sintered at 600°C for 15h. [•] Cu and glycine have synergistic effects on improvement of J c. [•] We illustrated the precipitation morphologies of secondary phase MgCu2 and MgO phases. [ABSTRACT FROM AUTHOR]

In order to prepare high performance oxide-dispersion-strengthened tungsten based alloys, the W-Y 2 O 3 composite powder precursors were synthesized by novel freeze-drying method. The average W grain size of prepared W-Y 2 O 3 composite powder is 14.2 nm, and corresponding grain size distribution is extremely narrow. The low-temperature sintered W-Y 2 O 3 alloys possess an ultrafine W grain size of about 410 nm while maintaining a comparatively high sintering density of 98.1%. The Y 2 O 3 particles (20–50 nm) with a W-Y-O diffusion layer and Y 2 WO 6 particles (<20 nm) distribute uniformly within W grains and especially at W grain boundaries. These W-Y-O phases adsorb free oxygen impurity, resulting in the purification and strengthening of W matrix. What's more, coherent or semi-coherent interfaces are observed between Y 2 WO 6 particles and W matrix, reinforcing the bonding strength of phase boundary. The combined action of the factors mentioned above leads to the hardness of sintered W-Y 2 O 3 alloys in our work as high as 690.2 ± 32.0 HV 0.2. These results indicate that the freeze-drying method and subsequent low temperature sintering is a promising method for preparing high performance W-Y 2 O 3 alloys with ultrafine grains. • The W-Y 2 O 3 powders of 14.1 nm were prepared by novel freeze-drying method. • The low-temperature sintered W-Y 2 O 3 alloys possess W grains of 400 nm meanwhile its density is 98.1%. • Nano oxide particles of 10∼30 nm uniformly distribute in W matrix. • Combining the interfacial relationship and the oxygen distribution, the mechanism of boundary purification and enhancement is proposed. [ABSTRACT FROM AUTHOR]

The effect of primary O phase on thermal compressive deformation behavior of a Ti 2 AlNb-based alloy are investigated at temperatures from 990 °C to 1020 °C and strain rate range from 0.001 s−1 to 1 s−1. The results indicated that the primary O phase has a significant effect on the hot deformation behavior of the studied alloy. The peak stress and the degree of the stress descent of the specimen with primary O lath and Widmanstätten O + B2 structures are higher than those of the specimen with Widmanstätten O + B2 structures under higher strain rate. Besides, both the critical stress and critical strain for the onset of dynamic recrystallization (DRX) of the studied alloy upsurge with increasing the strain rate or decreasing the deformation temperature. The specimen with primary O lath and Widmanstätten O + B2 structures exhibits greater critical stress and critical strain than the specimen with Widmanstätten O + B2 structures. The strain rate sensitivity exponents of the investigated alloy with primary O lath and Widmanstätten O + B2 structures is higher than that of the alloy with Widmanstätten O + B2 structures at low temperature (990 °C), while the reverse is true at high temperature (1020 °C). Beyond that, the DRX mechanisms of the explored alloys with different morphologies of O phase were also investigated by EBSD and TEM analysis. • Thermal deformation behavior of Ti 2 AlNb-based alloy with two morphologies of O phase was studied. • The existence of primary O lath results in more significant effect of flow softening. • Critical conditions for the onset of DRX is sensitive to morphology of O phase. • The studied Ti 2 AlNb-based alloys with different morphologies of O phase undergo DDRX in all deformation conditions. [ABSTRACT FROM AUTHOR]

With the aim of preparing high performance oxide-dispersion-strengthened tungsten based alloys by low temperature sintering, W–Y 2 O 3 composite nanopowders were prepared by novel hydrothermal synthesis method. The average size of W grain in these composite nanopowders is only 15.1 nm and corresponding grain size distribution is quite narrow. Studies on synthetic mechanism of powder precursors show that the Keggin structure of raw materials is destroyed during hydrothermal synthesis process, resulting in the formation of many W–OH bonds. Then W–OH bonds react with Y3+ to form W–O–Y bonds, which is a process of co-deposition in which elements are uniformly doped. The co-deposition mechanism also shed light on the approach to exploit other high quality powder systems. Then the low temperature sintering characteristics of these powders were investigated in details. It was found that the sintered W–Y 2 O 3 alloys possess refined W grains of about 210 nm while maintaining a relatively higher density of 98.0%. What's more, nano Y 2 O 3 particles (<50 nm) distribute uniformly within W grains and at W grain boundaries. The combined effect of the above factors leads to the hardness of sintered W–Y 2 O 3 alloys in our work as high as 726 ± 25 HV 0.2. Based on our results, the hydrothermal synthesis method is a promising way to prepare composite powder precursors for the sintering of high performance oxide-dispersion-strengthened tungsten based alloys with ultrafine grains and uniform oxide particles distribution. Image 1 • The W–Y 2 O 3 powders of 15.1 nm were prepared by novel hydrothermal synthesis method. • The new W–O–Y bonds are synthesized during hydrothermal process to achieve co-deposition. • The low-temperature sintered W–Y 2 O 3 alloys possess fine W grains of 210 nm meanwhile its density is 98.0%. • Nano oxide particles (<50 nm) uniformly distribute within W grains and at W grain boundaries. • The hardness of W–Y 2 O 3 alloys is as high as 725.6 ± 25.0 HV 0.2. [ABSTRACT FROM AUTHOR]