Advanced Materials Research Vols. 557-559

Abstract: Magnesia (MgO) is a fundamental component of many minerals found in nature and is used widely in our life, especially in refractory industry. However, the antihydration of MgO is a key concern in refractory suspension processing, MgO additions only in form of coarse particles(≥ 50 μm) or its contents of up to 10 wt.% are as a result of their high possibility to take place hydration reaction in water and the reaction can lead to volumetric expansion obviously. In the present work, citric acid (CA) can complex with Mg²⁺ in the MgO suspension under the condition of 4h and 25°C, and the deposit of magnesium ion-CA complexes become protective coating to inhibit magnesia react with water to form Mg(OH)₂.The test results of RSV of different additives shows CA is the best antihydration compound to inhibit MgO hydration comparing with EDTA-2Na，sodium pyrophosphate(SP)，trimeric sodium phosphate(TSP), which RSV is only 5.3ml when its dosage is 0.3%wt.

Abstract: Orthogonal experiments were employed to confirm the interactive effect of the addition of magnesium powder, milling time of aluminum powder, oxidization time of TiH2 on the pore structure of Aluminum foam, which prepared by PCM method. The results show that the three factors arragned in important order as the follows: oxidization time, milling time, and the quantity of magnesium powder. The high quality aluminum foam samples, with average porosity of 84.2%, average equivalent circle diameter of 1.9 mm and average circularity of 0.754, was made on the condition of milling time as 85 minutes, oxidization time as 10 minutes and magnesium powder content as 0.5 wt%.

Abstract: The effect of different hydrostatic extrusion ratios on the microstructure and mechanical properties of the ZK60 magnesium alloys were investigated. The results showed that, the major deformation mechanism of the alloy is twinning at room temperature, which resulted in that the tensile strengthen and hardness of the extruded alloy improved greatly. With deformation ratio increasing, the ultimate tensile strengthen and hardness are linearly increased, with the functions of Y= 4.2X+358.3 and Y=2.3X +73.69, respectively. And the maximum tensile strength and hardness of the extruded alloy are 383 MPa and 87HB, respectively. But the elongation decreases obviously, the minimum decreasing degree is 50%. With the deformation ratio increasing, the tendency of elongation rate increased as an “M” model.

Abstract: Reduction leaching of pyrolusite by cellulosic biomass,due to its good performace,low cost,renewable and environmental friendliness，has received increasing attention in recent years.In this work，the advances on reduction leaching of pyrolusite by cellulosic biomass are reviewed.The degradation mechanisms of cellulosic biomass and reduction leaching applicat- ions of pyrolusite by degradation products are analyzed．Finally，further study of the proposed reduction leaching of pyrolusite by cellulosic biomass are discussed．

Abstract: The mechanical performance and fracture of roll-bonded Cu/Al/Cu clad metal were investigated after heat treatment in the temperature range 200~500OC. In the roll-bonded 3-ply Cu/Al/Cu clad metal, no visible interfacial reaction compound and defects were observed at the interfaces, ensuring the well-bonded Cu/Al interface until the final moment of fracture in tension. The reaction layer was observed at the Cu/Al interface after annealing at and above 400OC, which deteriorated the ductility of clad metals. The thickness of the reaction layer increased with increasing heat treatment temperature. The periodic cracks were formed perpendicular to the tensile direction due to the strain mismatch between metal layers and the reaction compound layer in the clad heat treated at high temperatures at 500oC. The slip localization and delamination induced premature crack formation in Cu and Al layer, resulting in the decreased clad metal fracture strain, especially after heat treating at 500oC.

Abstract: The four kinds of Cu based friction materials with different micro-hardness were fabricated by sintering method, the Ti content of four kinds of Cu based friction material is 8%, 12%, 16% and 20%, respectively. The tribological properties were carried out on ring-to-block tester. The results show that the wear rates and the wear rates ratio of the pair and the friction material with lower micro-hardness were lower than that of friction material with higher micro-hardness, and lower wear rates ratio of pair and friction materials (WRRPF) is very helpful for protecting pair of friction materials.

Abstract: The influences of Mn and heat-treatment technology on microstructure and mechanical properties of medium-carbon-low-alloy wear-resistant cast steel were investigated. The results show that the hardness first increases and then drops down with the increase of Mn content, and the best hardness is 54HRC with Mn content 1.5%. The impact toughness first increases and then drops down with the increase of Mn content. The hardness and impact toughness first increase and then drop down with the increases of quenching temperature. The optimal impact toughness can be obtaind by quenching at 920°C and tempering at 200°C. Part of lower bainite and residual austenite and mass of tempered martensite are obtaind after tempering.

Abstract: Nb-5 at.% W-5 at.% Mo-2 at.%Zr-2 at.% C (Nb5522) bulk alloys were prepared using blended powders or ball-milled powders via spark plasma sintering. The differences between blended powder compacts and ball milled powder compacts with respect to their density, microstructure and mechanical properties were studied. The results showed that ball milling enhances the sinterability of Nb5522 powders. After sintered by SPS at 1873 K, the milled powders achieved a near-full densification density. The SPS process favors the precipitation of (Nb, Zr)C particles.

Abstract: Mechanical properties of Al-Mg porous materials which were made by self melting reactions at low temperatures are investigated in this work. The results showed that the yield strength of Al-20%Mg was up to 240 MPa, and this is the compressive characteristics of brittle porous materials. The excellent of mechanical properties of Al-Mg porous material was analyzed and the reason was ascribed to the homogenous distributed pore with cell wall strengthening.