查看更多>>摘要：Laser powder bed fusion(LPBF)is a commonly used additive manufacturing(AM)method for efficiently producing intricate geometric components.This investigation examines factors such as pores,cellular structure,grain size,and inclusions from the manufacturing process that contribute to the corrosion resistance of LPBF DSS.Furthermore,the as-built LPBF duplex stainless steel(DSS)is primarily ferrite due to the rapid cooling process.Therefore,the transformation of ferrite to austenite after various heat treatments in LPBF DSS and its corresponding corrosion resistance are presented.Additionally,a new mixed powder method is proposed to increase the austenite content in the as-built LPBF DSS.This review also focuses on the passivation capability and pitting corrosion performance in LPBF and conventional DSS.This article summarizes the variations in microstructure between as-built and heat-treated LPBF DSS,with their impacts on corrosion resistance,offer-ing insights for manufacturing highly corrosion-resistant LPBF DSS.
Andrea KellenbergerNicolae VaszilcsinMircea Laurentiu DanIon Mitelea...
607-619页
查看更多>>摘要：The components of proton exchange membrane water electrolysers frequently experience corrosion issues,especially at high anodic polarization,that restrict the use of more affordable alternatives to titanium.Here,we investigate localized corrosion processes of bare and Ti-coated AISI 446 ferritic stainless steel under anodic polarization by scanning electrochemical microscopy(SECM)in sodium sulphate and potassium chloride solutions.SECM approach curves and area scans measured at open-circuit potential(OCP)of the samples in the feedback mode using a redox mediator evidence a negative feedback effect caused by the surface passive film.For the anodic polarization of the sample,the substrate generation-tip collection mode enables to observe local generation of iron(Ⅱ)ions,as well as formation of molecular oxygen.For the uncoated AISI 446 sample,localized corrosion is detected in sodium sulphate solution simultaneously with oxygen formation at anodic potentials of 1.0 V vs.Ag/AgCl,whereas significant pitting corrosion is observed even at 0.2 V vs.Ag/AgCl in potassium chloride solution.The Ti-coated AISI 446 sample reveals enhanced corrosion resistance in both test solutions,without any evidence of iron(Ⅱ)ions generation at anodic potentials of 1.2 V vs.Ag/AgCl,where only oxygen formation is observed.
查看更多>>摘要：The present study focuses on investigating the microstructural evolutions and mechanical properties of energetic Al1(TiZrNbTaMoCr)15 refractory high-entropy alloys with the different heat treatments at low Al content state.It is found that even with a reduction in the Al content,the strength of these alloys remains unaffected at room temperature and high temperature,while the plasticity improves significantly.In particular,the coherent BCC/B2 microstructure with needle-like B2 nanoprecipitates dispersed into the BCC matrix is formed in 873 K-aged Al1Ti6Zr2Nb3Ta3Mo0.5Cr0.5 alloy.Therefore,this alloy exhibits the highest compression yield strength(σYS=1333 and 717 MPa)at room temperature and 1073 K,respectively.After 973 K-aged,the coherent BCC/B2 microstructure underwent destabilization,and the B2 phase transforms into the brittle Zr5Al3 phase which then coarsens and dominates the microstructure of S3-AITa3 alloy after 1073 K-aged.Moreover,these current alloys exhibit exceptionally high theoretical exothermic enthalpy(ΔH),surpassing 11606 J.g-1,which highlights their significant potential as innovative high-performance energetic structural materials.
查看更多>>摘要：The equiatomic TiNbZrTaHf alloy was successfully rolled at room temperature with the reduction of～85％.The microstruc-ture and tensile properties were investigated after cold working and annealing.It was determined that the recrystallization temperature of the TiNbZrTaHf alloy between 850 and 900 ℃.Complete recrystallization and normal grain growth occurred,the high stability of single phase was maintained after annealing at 1000,1200,and 1400 ℃.But the precipitated phase appeared after long term annealing,as seen after 500 h at 1000 ℃.After cold working,the tensile strength and the elonga-tion of TiNbZrTaHf were 1137 MPa and 25.1％,respectively.The annealed alloy has a high tensile strength(σb=863 MPa)and ductility(εe=28.5％).Moreover,the oxidation of TiNbZrTaHf alloy at elevated temperatures has a significant impact on its mechanical properties.The poor oxidation resistance of TiNbZrTaHf can accelerate tensile failure by inducing fractures at grain boundaries.
查看更多>>摘要：The phosphate protective film and micro-galvanic corrosion of biological Mg-3Zn-xNd(x=0,0.6,1.2)alloys were investi-gated by scanning and transmission electron microscopy,quasi-in-situ observation,scanning Kelvin probe force microscopy(SKPFM)and electrochemical tests.The results revealed the Mg-Zn-Nd phases formed in Mg-3Zn alloy contained with Nd.Adding Nd resulted in a significant decline in the cracks of the phosphate protective film and micro-galvanic corrosion of alloys,which were recorded by quasi-in-situ observation.In addition,the Volta potential difference of Mg-Zn-Nd/α-Mg(～188 mV)was lower than MgZn/α-Mg(～419 mV)and Zn-rich/α-Mg(～260 mV),and the corrosion rates of alloys mark-edly decreased after the addition of 0.6 wt％Nd.The improvement in corrosion resistance of Nd-containing alloys was mainly attributed to the following:(ⅰ)the addition of Nd reduced the Volta potential difference(second phases/α-Mg);(ⅱ)the phosphate protective film containing Nd2O3 deposited on the surface of the alloys,effectively preventing the penetration of harmful anions.
查看更多>>摘要：The high corrosion sensitivity and the potential bio-toxicity of Mg-Ag alloys limit their wide applications for the produc-tion of implanted devices.In the present work,Mn is added into the Mg-Ag alloy to optimize its corrosion behaviour.The corrosion behaviour of Mg-Ag-Mn alloys is investigated with the underlying microstructural factors examined.The Mg-Ag alloy with 2 wt％Mn exhibits the highest corrosion resistance after post-casting heat treatment at 440 ℃.The addition of Mn results in α-Mn phase with the incorporation of Fe,which suppresses the cathodic activity of impurity Fe.Further,heat treatment of the cast alloys homogenizes the distribution of Ag and promotes the precipitation of α-Mn phase.The former removes Ag segregations as potential cathodes;the latter promotes a more uniform distribution of cathodes and,therefore,prevents localized corrosion.
查看更多>>摘要：The effects of hydrostatic pressure,dissolved oxygen,temperature and flow velocity,and their interaction on the corrosion rates of E690 high-strength steel(HSS)in simulated marine environments were studied using response surface methodol-ogy.The results show that the flow velocity exerts the most significant influence on the corrosion rate of E690 HSS.Con-sequently,the corrosion behavior of E690 HSS under varying flow velocities were analyzed profoundly from initial pitting corrosion to long-term corrosion properties.The results indicate that the flow state facilitates the mass transfer and enhances the adsorption tendency of Cl-by enhancing the electrochemical activity of the steel surface.These factors accelerate the electrochemical reactions,resulting in increased pitting density,depth and the long-term corrosion rates in dynamic seawater environments.
查看更多>>摘要：Proper matching of cold-rolled deformation and low-temperature short-term aging can simultaneously enhance the strength and ductility of the lean duplex stainless steel.To investigate this,the microstructure evolution of cold-rolled and aging steels was observed by using scanning electron microscopy,transmission electron microscopy and electron backscattered diffrac-tion.Additionally,the phase volume fraction was measured using X-ray diffraction.In this study,it was observed that the elongation of 21Cr lean duplex stainless steel significantly increased to 16.7％after undergoing moderate cold deformation(～40％reduction)and subsequent aging treatment at 550 ℃ for 30 min.Remarkably,the material still maintained a high yield strength of 1045 MPa.Such an excellent mechanical property was attributed to a unique microstructure combination of fine α'-martensite,twins,coarsened austenite resulting from partial martensite reverse transformation,and two-phase fine layered structure.The result of this study may open up new horizons for the alloy development in order to overcome the low ductility of cold-rolled high-strength lean duplex stainless steel.
查看更多>>摘要：In this study,a high-carbon nano-bainitic GCr15SilMo bearing steel was investigated.Specifically,the effects of content and size of undissolved carbides on the microstructure and transformationkinetics of nano-bainite were analyzed.The results demonstrated that after prolonged austempering at low temperatures,the mixed microstructure composed of nano-bainite(NB),undissolved carbides(UC),and retained austenite(RA)was obtained in GCr15SiMo steel.When the experimental steel was austenitized at 900 ℃,the undissolved carbides gradually dissolved until reaching a stable state with increasing holding time.Furthermore,at the same austempering temperature,despite different volume fractions of undissolved carbides in the substrate,the volume fractions of nano-bainite in the final microstructures remained essentially the same.Moreover,the higher the content of undissolved carbides in steel,the faster the transformation rate of nano-bainite and the shorter the total transformation time.
查看更多>>摘要：This paper focuses on the relationship between the microstructure and tensile properties of Fe-Mn-Al-C low-density high-strength steel processes by hot-rolling and air-cooling process.The microstructure analysis reveals that the combination of hot-rolling and air-cooling results in the formation of heterogeneous structures comprising different-sized y and B2 phases in the low-density steel with the addition of nickel(Ni).The addition of Ni promotes the formation of the B2 phase and induces the pinning of B2 phase particles at the γ grain boundaries.This pinning effect effectively hinders the growth of the γ grains,leading to grain refinement.The tensile test results demonstrate that LDS-5Ni(low-density steel,LDS)exhibits excellent high strength and ductility combination,e.g.,a tensile strength of 1535 MPa,yield strength of 1482 MPa,and elongation of 23.3％.These remarkable mechanical properties are primarily attributed to the combined strengthening contributions of grain refinement and duplex nano-sized second-phase precipitation hardening.
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