Guang-chun Yao

Sound insulation property of Al-Si closed-cell aluminum foam bare board material

Abstract A1-Si closed-cell aluminum foam bare boards of 1 240 mm×1 100 mm with different densities and thicknesses were prepared by molten body transitional foaming process. The sound reduction index( R ) of AI-Si closed-cell aluminum foam bare boards was investigated experimentally under different frequencies (100-4 000 Hz). It is found that sound reduction index( R ) is small under low frequencies, large under high frequencies and is controlled by different mechanisms. The sound insulation property basically conforms with the monolayer board sound insulation theory. The sound reduction index( R ) increases with the even growth of thickness and density, but its rising trend is tempered. The single number sound reduction indexes( R w) of specimen with thickness of 20 cm and density of 0.51 g/cm 3 are 30.8 dB and 33 dB respectively, which demonstrates good sound insulation property for lightmass materials.

Preparation and characterization of aluminum foams with ZrH2 as foaming agent

Aluminum foams were fabricated by melt-based route using ZrH2 as a foaming agent. The factors which affected the foaming of aluminum foams during casting process were investigated. The powdered zirconium hydride with content of 0.6%-1.4% (mass fraction) was added to the molten pure aluminum and the foaming condition was controlled in a temperature range from 933 to 1 013 K, Ca amount of 1.5%-3.0% (mass fraction), stirring time of 0.5-2.5 min and holding time of 1.5-4.0 min to obtain homogeneous aluminum foams. The fabricated aluminum foams were characterized by XRD, SEM and Image-pro plus. The mechanical properties of the aluminum foams with different relative density were tested. The result indicates that the foaming agent (ZrH2) is suitable for the preparation of small aperture aluminum foams with average pore diameter of 1 mm. Inter-metallic compounds and Al2O3 have effect on the melt viscosity. The aluminum foams experience linear elastic, platforms and densification process and had a higher efficiency of energy absorption.

Three-point bending behavior of aluminum foam sandwich with steel panel

Static three-point bending tests of aluminum foam sandwiches with glued steel panel were performed. The deformation and failure of sandwich structure with different thicknesses of panel and foam core were investigated. The results indicate that the maximum bending load increases with the thickness of both steel panel and foam core. The failure of sandwich can be ascribed to the crush and shear damage of foam core and the delamination of glued interface at a large bending load. The crack on the foam wall developed in the melting foam procedure is the major factor for the failure of foam core. The sandwich structure with thick foam core and thin steel panel has the optimal specific bending strength. The maximum bending load of that with 8 mm panel and 50 mm foam core is 66.06 kN.

Effect of additive on corrosion resistance of NiFe2O4 ceramics as inert anodes

Abstract In order to improve the corrosion resistance of NiFe 2 O 4 ceramics as inert anode, additive V 2 O 5 was added to raw materials NiO and Fe 2 O 3. The inert anodes of nickel-ferrite ceramics were prepared by powder metallurgic method and the static corrosion rate in Na 3 AlF 6 -Al 2 O 3 was determined by mass loss measurement. The effect of V 2 O 5 on sintering property and corrosion resistance was studied. The results show that V 2 O 5 can promote the grain to develop completely and improve sintering property. EDS results show the reaction product Ni 2 FeVO 6 distributes along the grain boundary. The corrosion tests show that V 2 O 5 is beneficial to improving corrosion resistance remarkably. The reasons that V 2 O 5 can improve the corrosion resistance must be V 2 O 5 promoting the gains to develop completely and Ni 2 FeVO 6 distributes along the grain boundary. The stable structure can control the chemical dissolution of ceramics anode and the reinforced grain boundary can control the grain-boundary corrosion rate.

Tensile property of Al-Si closed-cell aluminum foam

Abstract Al-Si closed-cell aluminum foams of different densities were prepared by molten body transitional foaming process. The tensile behavior of Al-Si closed-cell aluminum foam was studied and the influence of relative densities on the tensile strength and elastic modulus was also researched. The results show that the fracture surfaces of Al-Si closed-cell aluminum foam display quasi-cleavage fracture consisting of brittle cleavages and ductile dimples. The tensile strength and elastic modulus are strictly affected by the relative density of Al-Si closed-cell aluminum foam. With increasing relative density, the tensile strength increases and the strain at which the peak strength is measured also increases; in addition, the elastic modulus increases with increasing relative density.

Electroless Ni-P plating on Mg-Li alloy by two-step method

Abstract Pretreated Mg-Li alloy sheets were pre-plated in a NiCO 3 ·2Ni(OH) 2 ·4H 2 O solution to form a thin Ni-P alloy film and then plating in a NiSO 4 ·6H 2 O solution was carried out to obtain a protective coating. The surface morphology, structure and corrosion resistance of the coating were studied. The results showed that a flat, bright and compact plating layer, which was integrated into the matrix metal, was obtained. The P content of the Ni-P coating reached 13.56% (mass fraction). The hardness value of the Ni-P coating was about HV 549. The polarization curve showed that the corrosion potential of the Ni-P coating reached −0.249 V (vs SCE). A long passivation region was found on the polarization curve, and this phenomenon indicated that the coating has an excellent anti-corrosion property.