Relationship among microstructure,mechanical properties and texture of TA32 titanium alloy sheets during hot tensile deformation

The relationship among microstructure,mechanical properties and texture of TA32 titanium alloy sheets during hot tensile deformation at 800℃was investigated.In the test,the original sheet exhibited relatively low flow stress and sound plasticity,and increasing the heat treatment temperature resulted in an increased ultimate tensile strength(UTS)and a decreased elongation(EL).The deformation mechanism of TA32 alloy was dominated by high angle grain boundaries sliding and coordinated by dislocation motion.The coarsening of grains and the annihilation of dislocations in heat-treated specimens weakened the deformation ability of material,which led to the increase in flow stress.Based on the high-temperature creep equation,the quantitative relationship between microstructure and flow stress was established.The grain size exponent andαphase strength constant of TA32 alloy were calculated to be 1.57 and 549.58 MPa,respectively.The flow stress was accurately predicted by combining with the corresponding phase volume fraction and grain size.Besides,the deformation behavior of TA32 alloy was also dependent on the orientation of predominantαphase,and the main slip mode was the activation of prismaticslip system.The decrease of near prism-oriented texture in heat-treated specimens resulted in the enhancement of strength of the material.

Shape controlling and property optimization of TA32 titanium alloy thin-walled part prepared by hot forming

The hot flow behaviors,microstructure evolution and fractographs were studied to optimize the hot forming process of the TA32 titanium alloy thin-walled part.A set of microstructure-based constitutive equations were developed based on the experimental data,which described the relationships among the hot flow stresses and the evolution of phase volume fraction,dislocation density,grain size and damage.The constitutive model was imported into ABAQUS 6.14 to simulate the hot forming process for a typical thin-walled part.The effective strain,dislocation density and damage distribution as well as forming defects of formed parts under different process parameters were predicted.A qualified part without wrinkling and fracture defects was produced at a loading speed of 5 mm/s at 800℃ by the modified blank shape,where the maximum damage value was only 18.3%.The accuracy of constitutive model and finite element(FE)simulation was verified by the microhardness tests,which indicates that the FE model based on physical internal-state variables can well optimize the hot forming process of TA32 titanium alloy complex parts.

Accelerated oxygen evolution kinetics on Ir-doped SrTiO_(3) perovskite by NH_(3) plasma treatment

Exploring low-cost and high-performance catalysts for oxygen evolution reaction(OER)remains to be a great challenge.Iridium-based perovskite oxide has large potential in OER because of its intrinsic activity and outstanding physicochemical properties.In this study,iridium-doped strontium titanate(Ir-STO)solution is brushed on a Ti sheet by the traditional method to obtain the Ir-STO/Ti electrodes after being calcined at a high temperature.The microstructure and electrocatalysis properties of the Ir-STO are further modified by a facile and scalable NH_(3)-plasma strategy.In addition to the doping of Ir,the NH_(3) plasma treatment further results in N-doping into Ir-STO,which enriches active species and causes oxygen vacancies near doped sites.The resulting N,Ir-STO/Ti electrode reveals excellent acidic OER activity with the lowest overpotential of 390 m V at 10 m A/cm^(2) and the smallest Tafel slope of 140 mV/dec after 10-min plasma treatment.Therefore,the great potential of activated N,Ir-STO/Ti is regarded as a catalyst for the OER,and thus making a new opportunity for developing other perovskite catalysts via NH_(3) plasma treatment.

Microstructure and hot flow stress at 970℃ of various heat-treated Ti2AlNb sheets

The microstructure and hot tensile behaviors of the different heat-treated Ti2AlNb sheets were investigated by backscattered electron image(BSE),electron backscattering diffraction(EBSD),transmission electron microscope(TEM)and tensile tests.The grain sizes and contents ofα2,B2/βand O phases were quantitatively studied.As the heating time increases at 970℃,the mean grain size and content ofα2-phase increased.The grain shapes and distributions of the O-phase lamellar grains were affected by the heat treatments.The plastic deformation promoted the O→B2/βphase transition and the globularization of O-phase lamellar grains at 970℃.Calculated by the creep equation and the iso-stress method,the grain size exponent wasμ=1.1 and the relationship between the material constants of B2/βand O phase was KO=1.14KB2/β.