查看更多>>摘要：Chloride-induced corrosion of steel reinforcement is the key factor leading to the degradation of reinforced concrete building durability.Improving the corrosion resistance of oxide scale of rebar has always been a research hotspot in the field of civil engineering materials.A ZIF-8 modified Ce-Sol-gel(ZCS)film was prepared on oxide scale of plain steel rebars by sol-gel method.It is observed that the|Z|0.01 Hz value of the ZCS film reached 320 kΩ cm2,which is about 29 times higher than that of blank rebar in simulated concrete pore(SCP)solution with 0.1 M NaCl.Then,they were inserted into mortar block and curing them in a curing box at T=20±2 ℃ and RH=95±2％for 28 days.Subsequently,these samples were subject to electrochemical impedance spectroscopy in 3.5 wt％NaCl.The|Z|0.01 Hz value of the rebar with the ZCS film was six times higher than that of the blank rebar after immersing for 20 days,resulting in an overall increase in corrosion resistance for rebar.The results indicated that the modification by ZIF-8 could reduce the porosity of Ce-sol-gel(CS)film and improved the"labyrinth effect"of the film.Additionally,the negative charge on the surface of ZIF-8 in alkaline condition increased the repulsion effect with Cl-,significantly reducing the sensitivity of rebar to Cl-.
查看更多>>摘要：High performance e-motors require a continuous enhancement of physical and mechanical properties for non-oriented electrical steel(NOES).However,the optimization of mechanical and magnetic properties simultaneously during NOES processing is extremely challenging where both properties directly influenced by alloy grain size,crystallographic texture,and dislocation density.In the current investigation,recrystallization annealing cycles were employed to modify the micro-structure with the aim of balance magnetic and mechanical properties of NOES concurrently.The results showed that with increasing annealing temperatures,the degree of recrystallization and grain size increased,while the dislocation density reduced considerably at the early stage of recrystallization.Meanwhile,the values of texture parameter A*verall(which is a function of overall individual grain orientations and their alignments with easy magnetization directions)were increased.It was evident that the magnetic properties were significantly improved,however the alloy strength was reduced with increasing annealing temperatures.Here,the correlation between magnetic properties as well as alloy strength on grain size,texture,and dislocation density were determined.From crystallographic texture intensity and measured properties quantitative analyses it was concluded that grain size was the predominant factor in balancing the mechanical and magnetic properties of the studied steel.Furthermore,the optimal comprehensive properties(both magnetic and mechanical)were achieved by annealing at 800 ℃,which yielded a magnetic induction B5000 of 1.616 T,a high-frequency iron lossP1.0/400 of 22.43 W/kg,and a yield strength of 527 MPa.
查看更多>>摘要：The oxidation behavior of 316L austenitic steel after thermal aging process at 600 ℃ for 6 h was investigated in the super-critical water(600 ℃/25 MPa)with 1000 h.Results showed that the grain size and the proportion of high angle grain boundaries(HAGB)increased in the steel after thermal aging process,with the observation of micro-textures.The weight gain rate of the steel after aging process increased,presenting the decreased Cr2O3 contain in the oxide layer,which resulted in the increasing diffusion rate of Fe and O ions in oxide layer.The molecular dynamics simulation results confirmed the high oxidation rate in HAGB and micro-textures for the 316L steel after aging process.
查看更多>>摘要：The aging embrittlement of 30Cr2Ni4MoV steel during service at high temperature has been attributed to the segregation of Si and Mn at grain boundary(GB).We report an alternative mechanism of aging embrittlement of 30Cr2Ni4MoV steel.Using atom probe tomography,it is found that the quenched and tempered(QT)30Cr2Ni4MoV steel has already contained obvious Si and Mn segregations at GB,which means that the Si and Mn segregations at GB are not sufficient to induce aging embrittlement.It is discovered for the first time in aged 30Cr2Ni4MoV there newly precipitate many G-phases along GB,and Si and Mn segregations at GB of QT30Cr2Ni4MoV steel are the main reason for the precipitation of G-phase.The hard and brittle G-phase helps to promote crack initiation during impact deformation.Subsequently,the cracks can rapidly propagate along GB due to the distribution of G-phase and the segregation of Si and Mn along the GB,which leads to intergranular cracking and low impact energy as for aged 30Cr2Ni4MoV steel.
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