Li Luoli

Effects of Rare Earths on Toughness of 31Mn2SiRE Wear-Resistance Cast Steel

Abstract The toughness of 31Mn2SiRE wear-resistance cast steel were increased by means of RE compound modification and high temperature austenitizing. The results show that the microstructures can be refined, needle and network ferrite are eliminated, the dislocation density and the quantity of dislocated martensite are increased remarkably, and the shape and distribution of inclusions are improved by the addition of RE. Therefore, the mechanical properties of the modified steel can be greatly increased, especially the toughness ( a K) by 44%, yield strength (σ 8 ) by 10%, and elongation (δ 5 ) by 42%.

Hydrothermal Synthesis of Nano-sized Cupric Tungstate (VI) Dihydrate and Its Synthesis Mechanism

Copper nitrate and sodium tungstate were employed to prepare nano-sized cupric tungstate (VI) dihydrate (CuWO4·2H2O) by hydrothermal method. Formation processes of Cu2WO4(OH)2 precursors were discussed, and the synthesis mechanism of CuWO4·2H2O precipitates from Cu2WO4(OH)2 precursors during the process of hydrothermal reaction was established. Morphological and microstructural investigations of precursors and precipitates were carried out using high resolution transmission electron microscopy (HRTEM) and X-ray diffractometer (XRD). Results show that the synthetic products CuWO4·2H2O particles are mostly spherical in the size range from 20 to 30 nm. Transmission electron microscopy (TEM) observations indicate that the formation of CuWO4·2H2O follows in situ crystallization mechanism in the process of hydrothermal reaction. In the long term hydrothermal environment of high pressure and temperature, Cu2WO4(OH)2 precursors are surrounded by WO42- ions, which are adsorbed and diffused on the surface of Cu2WO4(OH)2. By dehydrations and molecular rearrangement, CuWO4·2H2O precipitates heterogeneously nucleate here. WO42- ions react with Cu2WO4(OH)2 through CuWO4·2H2O layer until WO42- ions have been depleted.