Advanced Materials Research Vols. 146-147

Abstract: An ultrasonic fatigue testing system capable of operating at temperatures at 250 has been introduce to study the fatigue behavior of carbon manganese steels (A42 and A48) and loading frequency of approximately 20 kHz. Endurance limit results were comparable to those generated at room temperature to determine the effect of temperature. Scanning electron microscopy was then used to determine the initiation sites and the failure mechanisms. Initial results indicate that fatigue strength decrease a little at 250 , interior inclusions were the major microstructural feature responsible for crack initiation in the alloy.

Abstract: Ferrite content and the plate distance of pearlite of high carbon steel wire rod are analyzed by Optical Microscope and SEM, using quantitative microstructure analysis technology. The relation between microstructure and yield strength of high carbon steel wire rods was investigated. And the mathematical model of the relation was established as: σs(Pa)=104.52×106+161.70(1－fα 1/3)S－1(m). It was validated by experiment data that the mathematical model agrees well with the experimental results.

Abstract: There are many advantages of semi-solid processing technology such as energy saving, high efficiency and net-shaped processing. So it is a promising manufacturing technology in 21 century .It is the premise of getting the non-dendrite semisolid slurry to realize the semisolid processing.This paper reviewed the development of the technique of preparation for semi-solid state slurry and introduced some new researchment about the technique of preparation slurry for semi-solid processing. It researched a new technique of preparation for semi-solid state slurry—cooling by the sine function to produced the semi-solid state slurry. The result showed that the aluminum alloy melt was cooled and controlled nucleation and limited growth in the sine wave The fundamental principles through which sound semi-solid slurry can be effectively obtained were summarized.On the basis of the experiment and simulation，it analysised the temperature field and the flow field of the semisolid 2A12 slurry flow through sine passage. The result showed that there is the cooling and the self-stirring when the semisolid 2A12 slurry flow through sine passage. The fundamental principles through which sound semi-solid slurry can be effectively obtained were summarized. Finally, we presented a patent this simple process .

Abstract: The purpose of this paper is to investigate the influence of interphase properties on restored-tooth structure due to polymerization shrinkage of resin-based composite. The stress within the restored tooth structure built up from the polymerization shrinkage of the restorative composite was computed accounting for the time-dependent and viscoelastic behavior of the composite. A sensitivity study was performed to examine the relative influence of geometric and material parameters of an interphase on the shrinkage stress development. It was found that a correlation exists between material and geometry properties at the restoration-tooth interface and higher shrinkage stresses were located at the interphase due to polymerization shrinkage. The varying material and geometry properties of restoration-tooth interface seemed to have a conclusive effect on the interfacial stress system, as well as on the longevity of the restoration.

Abstract: Microstructures and macrosegregation of AZ80 magnesium alloy billets cast with and without the electromagnetic vibration were investigated. Compared with the conventional DC casting, microstructures of the billet have been greatly refined and the macrosegregation had been effectively reduced in electromagnetic vibration casting conditions. Increasing the electromagnetic vibration intensity, including both the stationary magnetic field and alternating magnetic field, leads to finer grains and more uniform distribution of solute elements in the billet.

Abstract: TiO2-SBA-15 surface (TSS) composites were prepared by the supercritical pretreatment and then sol-gel process with using paraffin used as a clogging agent. The as-grown materials were characterized by using X-ray diffraction, UV-VIS spectroscopy and nitrogen absorption. The photocatalytic activities of TSS were evaluated by quantifying the degradation of methylene blue solution under UV light. Compared with TiO2-SBA-15 (TS) composites prepared only by the sol–gel method, TSS composites remain in mesostructure with high surface areas due to clogging effect of paraffin on SBA-15 cavity. Additionally, the small crystalline size of TiO2 in TSS is attributed to the fact that silica support baffles the agglomeration ofTiO2 nanoparticles. In comparison of TS composites and pure TiO2, higher photocatalytic activity of TSS is obtained and mainly attributed to larger surface areas and greater band-gap energy.

Abstract: A two-dimensional cellular automaton model is developed to simulate the isothermal hot compression phase transformation of β→α in TA15 titanium alloy. The model, based on the data of hot compression deformation and some assumption, the phase transformation nucleation and growth function of the phase β→α which is utilized by the automaton in a probabilistic fashion. The probability of nucleation and growth of α phase is confirmed and described by the existing theories of dislocation density. The competition between phase transformation and growth of transitional phase is described by the changes of dislocation density in this cellular automaton lattice. Based on the results of cellular automaton, the transformation fraction of α phase is calculated with the number of lattice and isothermal phase transformation kinetic equation is also calculated with data of transformation fraction, and the effect of hot compression deformation parameters on phase transformation is also discussed.

Abstract: Thermo-gravimetric analysis (TGA) and Infrared Spectrum (IR) analysis were adopted to quantify the partially-carbonated profiles of concrete segment exposed to long-time natural carbonation. The results showed that the residual Ca(OH)2 content could be calculated by TGA, and the CaCO3 content formed by carbonation could also be quantified by IR. Thus the partial-carbonation profile illustrated by residual Ca(OH)2 distribution was lower than that by CaCO3 distribution, which indicates Ca(OH)2 and C-S-H gel were carbonated. Furthermore, the carbonation degree of concrete segment was lower than that of specimen because of dimension effect, which suggested that the small specimen could be used to assess carbonation related durability of concrete structures with good reliability.

Abstract: Ti-3.5Al-5Mo-4V-2Cr-1Fe-2Zr-2Sn titanium alloy is a new high strength metastable beta titanium alloy which was designed according to the principle of ‘near critical molybdenum equivalent and multicomponent strengthening’. The effect of solution treatment on aging responses of the new alloy including room temperature tensile properties and microstructures were investigated. There is a tendency that the tensile strength is increasing with the increase of solution temperatures on the same aging conditions and water quenching from solution temperatures can produce higher age hardening effect than that treated by air cooling. The results revealed that the specific aging response of the new alloy is from the high driving force of phase precipitation together with the effect of excess vacancies.

Abstract: Nanostructured surface layer was produced on Ti-6Al-4V alloy by surface mechanical attrition treatment(SMAT) technique, and the composite ceramic coatings of surface nanocrystallization/micro-arc oxidation(SNC/MAO) were prepared on the nanocrystallized surface of Ti-6Al-4V alloy by pulsed single-polar micro-arc oxidation in NaAlO2 solution. XRD, SEM and TEM techniques were used to investigate the phase and surface morphology of ceramic coatings and the influences on the surface state of the alloys. Meantime, the mechanical properties of Ti alloys were measured by tensile test. The results show that after the SMAT treatment for a short period of time, the surface layer was refined into ultrafine grains. The influences of the SMAT technique on the surface morphology of the ceramic coatings were also studied. The ceramic coatings are mainly composed of Al2TiO5, more compact and less porous than those untreated. The mechanical properties of Ti-6Al-4V alloy by SMAT technique are improved, compared with those untreated by SMAT technique.