Abstract: Steel constructions located in marine environments are exposed to more serious corrosion than in other environments, which result in great loss in lives and economy. So it is very important to carry out research work on the influence factor and mechanism of marine corrosion with necessary methods. In this paper, influence factors in marine environment of steels were discussed, the corrosion mechanism of five different zones in marine environment was summarized and the progress of research methods for marine corrosion was reviewed.
Abstract: In this research, fatigue behaviour of Ti-6Al-4V alloy was investigated for smooth and notched specimens with stress concentration factor(Kt) 3.6 and 4.1. This investigation was conducted for various diameter bars having different ultimate strength.Rotating bending fatigue test at R= -1 was emploied for this research. Notch sensitivity data was compared with those of steels. The result indicated that the presence of notch in this alloy has a different amount of sensitivity when the notch specimens were subjected to high cycle fatigue (HCF) and low cycle fatigue(LCF) tests.The notch sensitivity of this alloy was shown generally to be much lower than steel alloys with similar ultimate strength values. Therefore,considering the low sensitivity to notch of this alloy, can be recommended for applications with the presence of notch such as biomedical application
Abstract: (Pb, La) (Zr, Ti)O3 (PLZT) antiferroelectric thick films were deposited on Pt (111)/ Ti/SiO2/Si (100) substrates via sol-gel process. X-ray diffraction (XRD) analysis indicated that the films derived on Pt (111)/ Ti/SiO2/Si (100) substrates showed strong (111) preferred orientation. The Bulk and Surface silicon of micromachining process were employed in the silicon-based antiferroelectric thick film microcantilever fabrication, such as wet chemical etching for PLZT, inductive couple plasmas (ICP)for silicon etching, platinum etching and so on. Challenges such as Pt/Ti bottom electrode and morphology of PLZT thick film were solved, the integration of functional antiferroelectric materials and MEMS technology, provide a new way of thinking for the design and manufacture of micro-actuators.
Abstract: The effect of strain on the microstructure evolution of Fe-32%Ni alloy during multi-axial forging at the temperature of 500°C and a strain rate of 210-2 s-1 was investigated by optical microscope (OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and electron back scatter diffraction (EBSD) observations. The results show that the austenite grains were greatly refined with increasing cumulative strain, and the microstructure evolution during multi-axial forging can be summarized as such a process that deformation bands crossing each other subdivide the original austenite grain into several sub-grains and then these sub-grains are subdivided into more small ones and gradually angled to new independent grains with their boundaries transformed into large angle boundaries in subsequent compression.
Abstract: The temperature memory effect of shape memory alloy (SMA) induced by an incomplete martensitic inverse phase transformation has the potential values in various engineering fields. It is of theoretical and practical interests to establish a phase transformation model which overcomes the limitation that previous phase transformation models of SMA fail to take into account the temperature memory effect. In this paper, the curves of heat flow versus temperature of SMA during the martensitic phase transformation and martensitic inverse phase transformation are described as the quadratic functions of temperature. A new phase transformation model of SMA is developed based on the differential relationship between martensitic volume fraction and phase transformation free energy. Numerical results show that the new model well predicts the phase transformation behaviors of SMA associated with the temperature memory effect.
Abstract: 2A12 specimens are selected in pre-corrosion fatigue test to get the ground corrosion effect coefficient, namely C(t) curve. Then, combining with Miner linear cumulative damage theory, theoretical fatigue life model is established based on the simulated corrosion-fatigue interactive process. Compared with actual corrosion-fatigue interactive test, theoretical life in short interactive periods is almost same, but actual life is higher in long interactive periods. Afterwards, a modified model based on C(t) curve at different interactive periods is established. The calculation shows that the modified results are in good agreement with the corrosion-fatigue interactive test.
Abstract: Shrinkage porosity defects occurring in ring groove underside the pin hole of aluminum piston are strongly influenced by the time-varying temperature profiles inside the solidifying casting. By adopting the finite element analysis software PROCAST and combining with production practice, the gating system which has open-cycle ring feeding channel in the bottom of the piston was compared with conventional techniques; the influence of opening angle of ring feeding channel and different process parameters on shrinkage distribution was researched. The results show the gating system with open-cycle ring feeding channel can satisfy progressive solidification and effectively eliminate the shrinkage in ring groove underside piston pin hole, and can greatly reduce the riser size and improve casting yield; the opening angle influences shrinkage distribution and can be adjusted to achieve effective feeding; shrinkage size is influenced by pouring temperature and casting speed which have less effect on shrinkage distribution. The system of ring feeding channel is adopted, the opening angle and process parameters are adjusted, all which can effectively eliminate shrinkage in the bottom of the piston, improve casting yield and process rate.
Abstract: The effect of the middle heat treatment+aging(1323K+1073K) for the precipitation mechanism and volume fraction of Ni-11at.%Cr-17at.%Al ternary alloy are studied based on microscopic phase-field model. The results show that the precipitation mechanism is non-classical nucleation and growth for the alloy at middle heat treatment, and the congruent ordering and spinodal decomposition mechanism occur at single-stage aging. The larger precipitation strengthening phases are obtained, the volume fraction of ordering phases and the averaged ordering parameter are higher, and the incubation period prolongs after the middle heat treatment.
Abstract: The effects of process parameters on evolution of microstructures of 7055 aluminum alloy in creep age forming were studied and the microstrucures were analyzed using transmission electron microscopy (TEM). Some important results are obtained: with the increasing of ageing time, the size of platelet shaped (known as Guinier-Preston (G-P) zones) precipitates and spherical shaped η' precipitates increased, the number of platelet shaped precipitates increased too, while the number of η' precipitates decreased; the precipitates with almost the same size distributed continuously and uniformly along the grain boundary with quite narrow precipitate free zones (PFZs) at 5 hours of ageing time, when the ageing time increases to 8 hours, the distribution of the precipitates along the grain boundary becomes discontinuous and the PFZs gets wider, while with the further increasing of the ageing time, the precipitates distributed continuously again along the grain boundary and the PFZs become more wider. From comparison of stress-aged alloy to stress-free-aged alloy, it was found that after 20 hours ageing, the precipitates in the stress-aged alloy are slightly coarser and the PFZs are wider, the density of retained η' is lower with the development of η phase.