High-pressure die cast(HPDC)AZ91 magnesium alloy is widely used in automotive components such as transmission housings and brackets for its excellent strength-to-weight ratio.Zinc-based cold spray coatings can be appl...High-pressure die cast(HPDC)AZ91 magnesium alloy is widely used in automotive components such as transmission housings and brackets for its excellent strength-to-weight ratio.Zinc-based cold spray coatings can be applied selectively to vulnerable areas to enhance corrosion resistance,minimize galvanic coupling with dissimilar metals,and eliminate the need for full-surface oxide coatings,making the process more efficient and targeted.A comprehensive evaluation of 16 combinations of nitrogen carrier gas temperatures and pressures led to the identification of an optimal range of process parameters,yielding Zn coatings with porosity<0.5% by area,wear rates reduced by a factor of two compared to uncoated AZ91,and adhesion strengths up to 35 MPa.The enhanced mechanical performance of the coating is attributed to the low porosity and the formation of a metallurgical bond at the coating-substrate interface.Corrosion studies using macroscale potentiodynamic polarization(PDP)and electrochemical impedance spectroscopy(EIS)revealed a significant decrease in corrosion rate and a shift to more noble corrosion potentials(ZCP)for coated substrates.Furthermore,the Zn cold-sprayed samples exhibited significantly lower corrosioninduced evolved hydrogen content compared to the base AZ91 substrate and AZ91 coated with industrial coatings,demonstrating that the Zn layer effectively protects the substrate from the corrosive environment.Overall,cold spray Zn coatings significantly improve the mechanical and corrosion performance of AZ91 Mg alloys,addressing key material challenges and enabling their broader use in automotive applications.展开更多
We demonstrate generalizable semantic segmentation using minimal ground truth data.Correlated scanning electron microscopy(SEM)images and electron backscatter diffraction(EBSD)measurements of friction-stir processed 3...We demonstrate generalizable semantic segmentation using minimal ground truth data.Correlated scanning electron microscopy(SEM)images and electron backscatter diffraction(EBSD)measurements of friction-stir processed 316L stainless steel plates were used to train deep learning models for grain boundary segmentation.Secondary electron(SE)imaging taken at 10 keV correlated to EBSD-derived grain boundaries produced the best performing model.Notably,an ensemble of three models trained on a single SE image produced accurate segmentation over a series of backscatter electron(BSE)images of samples manufactured under different processing parameters,with a mean absolute error in grain size of 0.34μm.The generalizability of the models likely results from the similar escape depths of the SE training input and the EBSD training output and the reduced probability of stored strain artifacts appearing in the image.This highlights the importance of considering the physical principles behind imaging to develop robust models for microstructure characterization.展开更多
基金the support of the U.S.Department of Energy’s Vehicle Technologies Office.
文摘High-pressure die cast(HPDC)AZ91 magnesium alloy is widely used in automotive components such as transmission housings and brackets for its excellent strength-to-weight ratio.Zinc-based cold spray coatings can be applied selectively to vulnerable areas to enhance corrosion resistance,minimize galvanic coupling with dissimilar metals,and eliminate the need for full-surface oxide coatings,making the process more efficient and targeted.A comprehensive evaluation of 16 combinations of nitrogen carrier gas temperatures and pressures led to the identification of an optimal range of process parameters,yielding Zn coatings with porosity<0.5% by area,wear rates reduced by a factor of two compared to uncoated AZ91,and adhesion strengths up to 35 MPa.The enhanced mechanical performance of the coating is attributed to the low porosity and the formation of a metallurgical bond at the coating-substrate interface.Corrosion studies using macroscale potentiodynamic polarization(PDP)and electrochemical impedance spectroscopy(EIS)revealed a significant decrease in corrosion rate and a shift to more noble corrosion potentials(ZCP)for coated substrates.Furthermore,the Zn cold-sprayed samples exhibited significantly lower corrosioninduced evolved hydrogen content compared to the base AZ91 substrate and AZ91 coated with industrial coatings,demonstrating that the Zn layer effectively protects the substrate from the corrosive environment.Overall,cold spray Zn coatings significantly improve the mechanical and corrosion performance of AZ91 Mg alloys,addressing key material challenges and enabling their broader use in automotive applications.
文摘We demonstrate generalizable semantic segmentation using minimal ground truth data.Correlated scanning electron microscopy(SEM)images and electron backscatter diffraction(EBSD)measurements of friction-stir processed 316L stainless steel plates were used to train deep learning models for grain boundary segmentation.Secondary electron(SE)imaging taken at 10 keV correlated to EBSD-derived grain boundaries produced the best performing model.Notably,an ensemble of three models trained on a single SE image produced accurate segmentation over a series of backscatter electron(BSE)images of samples manufactured under different processing parameters,with a mean absolute error in grain size of 0.34μm.The generalizability of the models likely results from the similar escape depths of the SE training input and the EBSD training output and the reduced probability of stored strain artifacts appearing in the image.This highlights the importance of considering the physical principles behind imaging to develop robust models for microstructure characterization.
