We link different microstructures to tribological behaviors of Ti-50.8 Ni(mole fraction, %) in reciprocating mode at room temperature(20 ℃). Hot-rolled alloys with B2 phase exhibit lower coefficient of friction and w...We link different microstructures to tribological behaviors of Ti-50.8 Ni(mole fraction, %) in reciprocating mode at room temperature(20 ℃). Hot-rolled alloys with B2 phase exhibit lower coefficient of friction and wear rate compared to the ones with B19?. Stress-induced martensitic transformation occurs during sliding. However, multi-pass hot rolling weakens the wear resistance. In this study, microstructures were characterized through electron backscatter diffraction and transmission electron microscopy(EBSD/TEM). From the concept of energy conservation, the effects of weak intensity of hot-rolled textures on the wear resistance are minimal. Based on the result that the alloy with a higher portion of coincidence site lattice boundaries shows lower martensitic start transformation temperature in the DSC curves than that with higher KAM values, the delay on B2-B19? transformation from {112}B2 twins outweighs dislocations. Moreover, widely distributed small-angle grain boundaries owing to dynamic recovery improve the wear resistance effectively compared to those that are well-recrystallized.展开更多
The microstructure characteristics of TiNi alloy were investigated to elucidate the active deformation mechanisms during hot rolling and the corresponding tribology performance.The deformation was mainly dominated by ...The microstructure characteristics of TiNi alloy were investigated to elucidate the active deformation mechanisms during hot rolling and the corresponding tribology performance.The deformation was mainly dominated by a combination of mechanical twinning involving the {114}_(B2) and {112}_(B2) twins,dislocations,and stacking faults during the manufacturing process.Moreover,various heat treatments were performed to differentiate the discrepancies in tribological behaviors of hot-rolled and heattreated alloys.Hot-rolled microstructures with high defect density approximate to nanoscale precipitates through aging as the wear resistance of the alloy improves,albeit it is softer compared to the aged one.As demonstrated by the X-ray diffraction(XRD) results of the wear tracks,microstructures undergo the stress-induced martensitic(SIM) transformation during dry sliding.From differential scanning calorimetry(DSC) analysis,the martensitic transformation temperature is lowered by defects in the austenite phase.The activation of the SIM transformation can be a sluggish process owing to the effect of twinning,where both primary and secondary twins are involved.Furthermore,a reversible transformation that is related to pseudoelasticity causes a decrease in wear volume at room temperature,which is higher than the austenite finish temperature.Meanwhile,abrasive wear advances toward adhesion.Additionally,the hot-rolled sheet with y fiber-{111}//ND(normal direction) exhibits better wear resistance compared to the sheet with α fiber-{100}//ND.展开更多
The frequentist model averaging(FMA)and the focus information criterion(FIC)under a local framework have been extensively studied in the likelihood and regression setting since the seminal work of Hjort and Claes kens...The frequentist model averaging(FMA)and the focus information criterion(FIC)under a local framework have been extensively studied in the likelihood and regression setting since the seminal work of Hjort and Claes kens in 2003.One inconvenience,however,of the existing works is that they usually require the involved criterion function to be twice differentiable which thus prevents a direct application to the case of quantile regression(QR).This as well as some other intrinsic merits of QR motivate us to study the FIC and FMA in a locally misspecified linear QR model.Specifically,we derive in this paper the explicit asymptotic risk expression for a general submodel-based QR estimator of a focus parameter.Then based on this asymptotic result,we develop the FIC and FMA in the current setting.Our theoretical development depends crucially on the convexity of the objective function,which makes possible to establish the asymptotics based on the existing convex stochastic process theory.Simulation studies are presented to illustrate the finite sample performance of the proposed method.The low birth weight data set is analyzed.展开更多
基金financially supported by the National Natural Science Foundation of China-Aerospace Science and Technology Corporation of China Aerospace Advanced Manufacturing Technology Research Joint Fund (U1737204)the National Natural Science Foundation of China (51673205)the Key Research Program of Frontier Science,Chinese Academy of Sciences (QYZDJ-SSW-SLH056)。
文摘We link different microstructures to tribological behaviors of Ti-50.8 Ni(mole fraction, %) in reciprocating mode at room temperature(20 ℃). Hot-rolled alloys with B2 phase exhibit lower coefficient of friction and wear rate compared to the ones with B19?. Stress-induced martensitic transformation occurs during sliding. However, multi-pass hot rolling weakens the wear resistance. In this study, microstructures were characterized through electron backscatter diffraction and transmission electron microscopy(EBSD/TEM). From the concept of energy conservation, the effects of weak intensity of hot-rolled textures on the wear resistance are minimal. Based on the result that the alloy with a higher portion of coincidence site lattice boundaries shows lower martensitic start transformation temperature in the DSC curves than that with higher KAM values, the delay on B2-B19? transformation from {112}B2 twins outweighs dislocations. Moreover, widely distributed small-angle grain boundaries owing to dynamic recovery improve the wear resistance effectively compared to those that are well-recrystallized.
基金financially supported by the National Natural Science Foundation of China (Nos. U1737204and 51673205)the Key Research Program of Frontier ScienceChinese Academy of Sciences (No. QYZDJ-SSW-SLH056)。
文摘The microstructure characteristics of TiNi alloy were investigated to elucidate the active deformation mechanisms during hot rolling and the corresponding tribology performance.The deformation was mainly dominated by a combination of mechanical twinning involving the {114}_(B2) and {112}_(B2) twins,dislocations,and stacking faults during the manufacturing process.Moreover,various heat treatments were performed to differentiate the discrepancies in tribological behaviors of hot-rolled and heattreated alloys.Hot-rolled microstructures with high defect density approximate to nanoscale precipitates through aging as the wear resistance of the alloy improves,albeit it is softer compared to the aged one.As demonstrated by the X-ray diffraction(XRD) results of the wear tracks,microstructures undergo the stress-induced martensitic(SIM) transformation during dry sliding.From differential scanning calorimetry(DSC) analysis,the martensitic transformation temperature is lowered by defects in the austenite phase.The activation of the SIM transformation can be a sluggish process owing to the effect of twinning,where both primary and secondary twins are involved.Furthermore,a reversible transformation that is related to pseudoelasticity causes a decrease in wear volume at room temperature,which is higher than the austenite finish temperature.Meanwhile,abrasive wear advances toward adhesion.Additionally,the hot-rolled sheet with y fiber-{111}//ND(normal direction) exhibits better wear resistance compared to the sheet with α fiber-{100}//ND.
基金This paper is supported by the National Natural Science Foundation of China(No.11771049).
文摘The frequentist model averaging(FMA)and the focus information criterion(FIC)under a local framework have been extensively studied in the likelihood and regression setting since the seminal work of Hjort and Claes kens in 2003.One inconvenience,however,of the existing works is that they usually require the involved criterion function to be twice differentiable which thus prevents a direct application to the case of quantile regression(QR).This as well as some other intrinsic merits of QR motivate us to study the FIC and FMA in a locally misspecified linear QR model.Specifically,we derive in this paper the explicit asymptotic risk expression for a general submodel-based QR estimator of a focus parameter.Then based on this asymptotic result,we develop the FIC and FMA in the current setting.Our theoretical development depends crucially on the convexity of the objective function,which makes possible to establish the asymptotics based on the existing convex stochastic process theory.Simulation studies are presented to illustrate the finite sample performance of the proposed method.The low birth weight data set is analyzed.
