Advanced Materials Research Vols. 1120-1121

Abstract: Aimed at the corrosion problem of DH36 steel in the seawater full immersion zone, corrosion environment of full immersion zone has been simulated with artificial seawater in laboratory. The corrosion behaviors of DH36 steel in the full immersion zone were investigated by using full immersion tests. The morphology of corrosion products was observed by SEM. Using linear regression analysis to establish the relationship between temperature and the corrosion of DH36 steel. The results showed that the corrosion of DH36 steel immersed in full immersion zone corroded seriously, and the corrosion rate of DH36 steel increased with temperature increasing.

Abstract: In the present paper, based on Bi-containing hypereutectic Al-20%Si alloy, a rotating magnetic field was used, the microstructures of the alloy have been observed and analyzed by optical microscope and scanning electronic microscope, and its wear-resisting property was measured. The influence mechanism of rotating magnetic field on the microstructures and properties of the alloy has been discussed. Research results show that exerting a rotating magnetic field in the hypereutectic Al-20%Si alloy drastically decreases the amount of primary Si phase, only some tiny bulk Si exist and the amount of needle eutectic Si increase. The dendrite-like primary α-Al appears at the same time. With the increase of stirring rate of rotating magnetic field, the change way of eutectic Si shape is coarse needle→tiny needle→coarse needle; the rotating magnetic field can change the nonuniform distribution of Bi induced by Bi local decentralization. With the increase of stirring rate of rotating magnetic field, the change way of Bi shape in upper part microstructures of the alloy is large bulk→short rodlike→big globular→small globular, Bi local decentralization is changed into uniform distribution; In addition, exerting a rotating magnetic field in the hypereutectic Al-20%Si alloy can increase wear-resisting property of the alloy.

Abstract: The dynamic compression test was carried out for the AZ91 Magnesium alloy of as-cast and aging state with a split Hopkinson pressure bar, and the dynamic behavior has been investigated. Finally the fracture surface of samples at the different strain rates was analyzed by scanning electron microscope (SEM). The results show that compared with the as-cast AZ91, it is more impressible for the solid solution and age-treatment AZ91 at the similar strong strain rates, while the stress-strain curve has the duality of positive and negative effects as the variation of strain rate.

Abstract: In order to provide the best technic parameter for hot pressing, the distributions of Fe and Be near the Be and 00Cr17Ni14Mo2 stainless steel (Be/SS) diffusion bonding interface under different technic parameter were simulated by the finite element method and measured by means of scanning auger microspectroy (AES). The simulated results were compared with experimental value, The distributions of Fe and Be near the Be/SS diffusion bonding interface and the relationships between the width of diffusion layer, the heating temperature, the holding time and the pressure were also discussed. The results indicate that under the condition of heating temperature 1323K and 1023K with diffusion pressure 60MPa and holding time 7200s, respectively, the simulated distributions of Fe and Be near the Be/SS diffusion bonding interface fit with the experimence values, and the width of diffusion layer at 1323K is about 2.5 times the one at 1023K. Under the condition of heating temperature 1023K with holding time 7200s, the width of diffusion layer measured at 30MPa, 40MPa, 50MPa and 60MPa is fit well with the simulated results and the relationship between the width of diffusion layer (x/μm) and the diffusion pressure (p/MPa) follows the eqution 0f x =-1.5×10^-2p² +2.8275p -0.1575. Under the condition of heating temperature 1023K with diffusion pressure 60MPa, the simulation curve between the width of diffusion layer (x/μm) and the holding time (t/s) follows the eqution 0f x=10t³-60.571t²+135.64t+0.2143.

Abstract: During solidification of metallic alloys, coalescence corresponds to the formation of solid bridges between grains when both solid and liquid phases are percolated. As such, it represents a key transition with respect to the mechanical behaviour of solidifying alloys and to the prediction of solidification cracking. Coalescence starts at the coherency point when the grains begin to touch each other, but are unable to sustain any tensile loads. It ends up at the rigidity temperature when the solid phase is sufficiently coalesced to transmit macroscopic tensile strains and stresses. This temperature, also called mechanical or tensile coherency temperature, is a major input parameter in numerical modelling of solidification processes as it defines the point at which thermally induced deformations start to generate internal stresses in a casting. The rigidity temperature has been determined in Al Zn alloys using in situ X-ray diffraction (XRD) during casting in a dog bone shaped mould. This set-up allows the sample to build up internal stress naturally as its contraction is prevented. The cooling on both extremities of the mould induces a hot spot at the middle of the sample which is irradiated by X-rays. Diffraction patterns were recorded every 0.5 s using a detector covering a 426 x 426 mm² area. The change of diffraction angles allowed us to observe agglomeration/decohesion of growing grain clusters and to determine a solid volume fraction at rigidity around 98 % depending on solidification time for grain refined Al 6.2 wt% Zn alloys.

Abstract: A P20 steel are machined in the milling speed range of 200 to 942m/min. The morphology and formation of the chips are investigated at various speeds. The serrated chips with adiabatic shear band are observed at a high milling speed. The transition from continuous to serrated chip formation is favored by the increase in work material hardness and milling speed. The study assumes that the chip segmentation is only induced by adiabatic shear banding, without material failure in the primary shear zone. Based on adiabatic shear theory, using the JC and the power material constitutive equation, the modified material model which takes into a strain softening is developed for prediction of the serrated chip formation. Experimental measurements are compared with the simulation results.

Abstract: Padding assisted roll-bending process is an advanced method to manufacture cylindrical thin-walled structure with variable thickness. A finite element model was established to study the deformation behavior of the padding assisted roll-bending process. In the numerical simulation model, aluminum sheet was selected as an elasto-plastic model, and nylon material was as an elastic model. The research results show that the radius of roll-bent thin-walled aluminum cylinder decreases with increasing of padding material’s stiffness, decreasing of the thickness ratio of nylon-to-metal and increasing of the roller stroke, and that an appropriate thickness compensation of padding material can improve the curvature consistency of cylindrical thin-walled structure with variable thickness.

Abstract: This research paper deals with an investigation of the fluidity of plastic blends with a recycled filler. Five different blends with three filler concentrations were prepared. As a fillers were radiation crosslinked plastics used. Fluidity was determined by the spiral test where a cavity with the Archimedes spiral is used and a length of the resulting spiral is evaluated and compared. Results show that the more filler is used the worse fluidity there is; however lower concentrations have fluidity almost identical to the non-filled material and the difference is almost negligible. At higher concentrations is the difference more significant and thus it has to be taken into account. Particle size of the filler should be also taken into a consideration but its influence greatly depends on the matrix.

Abstract: Influence of mechanical properties of the hard surface layer of modified polyamide 6 is studied. Mechanical properties are acquired by nanohardness test with using the DSI method (Depth Sensing Indentation). Hard surface layers are created by radiation cross-linking technology. This technology allows polymer materials modification followed by the change of their end-use properties. The surface layer of polymer material is modified by ionizing β - radiation. When the polymer material is exposed to the β radiation, it is possible to observe changes of the surface layer at applied load. Radiation cross-linking usually improves strength, reduces creep, contributes to chemical resistance improvement, and in many cases improves tribological properties.

Abstract: In this study there was found that ionizing beta radiation increased the strength of bonded joints and improved the adhesion properties of polypropylene (PP). Generally, for the formation of quality bonded joint it is important to wet the adhesive bonding surface well. Wettability is characterized by the contact angle of wetting. The liquid has to have a lower surface tension than the solid in order to be able to wet the solid substance. The measurement results indicated that ionizing beta radiation was a very effective tool for the improvement of adhesive properties and increased the strength of bonded joints of polypropylene. Bonded surfaces with ionizing beta radiation doses of 0, 33, 66 and 99 kGy were irradiated. The best results were achieved by irradiation at dose of 66 kGy by which the highest surface energy and the highest strength of bonded joints of PP were achieved. The strength of bonded joints after irradiation was increased up to 450 % compared to untreated material. A similar trend was observed even for surface energy.