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Abstract: The phase evolution and magnetic properties of Pr x Fe82−x−y Ti y Co10B4C4 (x =9–10.5; y =0, 2) melt-spun ribbons have been investigated. The effects of wheel speed and annealing on the crystallization and magnetic properties of the ribbons are discussed in detail. It was found that Ti substitution enhances the glass forming ability of the Pr2(Fe, Co)14(C, B)-type ribbons. For a high wheel speed V s (18m/s), the Ti-substitution ribbons consist of a significant fraction of amorphous phase, and show typical two-step magnetic behavior, while most of the Ti-free ribbons are mainly composed of the crystalline 2:14:1, α-(Fe, Co) and 2:17 phases. With decreasing wheel speed, all ribbons are fully crystallized, and a larger fraction of the magnetically hard 2:14:1 phase is formed. The content of metastable 2:17 phase in the ribbons decreases with increasing Pr and Ti substitution. A B r of 9.5kG, i H c of 9.8kOe, and (BH)max of 16.0MGOe were obtained in the as-spun Ti-substituted Pr10.5Fe69.5Ti2Co10B4C4 ribbon prepared at V s =15m/s. For all the as-spun, Ti-free ribbons prepared at various V s, the (BH)max is lower than 10MGOe owing to a poor shape of the demagnetization curve. Ti substitution also helps suppress the grain growth of 2:17 phase during the annealing process, and simultaneously promotes the growth of magnetically hard 2:14:1 phase. The annealing treatment significantly improves the magnetic properties of the Ti-substituted ribbons with higher Pr contents. No obvious improvement of magnetic properties was found in the Ti-free ribbons after annealing. [Copyright &y& Elsevier]

Abstract: Sialon–Si3N4 graded nano-composite ceramic tool materials with five-layered symmetrical distribution were fabricated by using hot pressing technique. Mechanical property tests have been conducted to determine the optimal structural parameters and sintering parameters. The residual stresses in the surface layer of the graded ceramic tool materials were calculated by the indentation method. The experiment results showed that Sialon–Si3N4 graded ceramic tool materials with a thickness ratio of 0.3, which were sintered under a pressure of 35MPa at a sintering temperature of 1700–1750°C for 60min, had optimum mechanical properties. And the graded structure can induce residual compressive stresses in the material surface layer. The characterization revealed a typical duplex distribution with small β-Si3N4 grains embedded in the matrix of large β-Si3N4 grains. This duplex microstructure can contribute to the improvement of flexural strength and fracture toughness. Additionally, a mix of intergranular and transgranular fracture, crack deflection and crack bridging in the material surface layer contributed to the strengthening and toughening mechanisms for Sialon–Si3N4 graded ceramic tool materials. [Copyright &y& Elsevier]

Pure and Cu doped MgB2 think films have been prepared on Cu, Ni and stainless steel substrates using a short-time sintering method. Results showed that single MgB2 phase films can be easily formed in a short period of time (3 min) at temperatures above 700 °C. Un-doped MgB2 films were found to be loosely attached to the Ni and stainless steel substrates. However, the MgB2 with Cu powders addition adhered well to the substrates without serious degradation of Tc and flux pinning. The Jc increased one order of magnitude and irreversibility field determined from M–H loops also increased when sintering temperature increased from 745 to 900 °C. Jc values in the range of 1–9×105 A/cm2 at 15 K have been achieved for both doped and un-doped films sintered at 900 °C for 3 min. [Copyright &y& Elsevier]