Metal additive manufacturing(AM),as a disruptive technology in the feld of fabricating metallic parts,has shown its ability to design component with macrostructural complexity.However,some of these functionally comple...Metal additive manufacturing(AM),as a disruptive technology in the feld of fabricating metallic parts,has shown its ability to design component with macrostructural complexity.However,some of these functionally complex structures typically contain a wide range of feature sizes,namely,the characteristic length of elements in AM-produced components can vary from millimeter to meter-scale.The requisite for controlling performance covers nearly six orders of magnitude,from the microstructure to macro scale structure.Understanding the mechanical variation with the feature size is of critical importance for topology optimization engineers to make required design decisions.In this work,laser metal deposition(LMD)is adopted to manufacture 316L stainless steel(SS)samples.To evaluate the efect of defects and specimen size on mechanical properties of LMD-produced samples,fve rectangular sample sizes which ranged from non-standard miniature size to ASTM standard sub-sized samples were machined from the block.Tensile test reveals that the mechanical properties including yield strength(YS),ultimate tensile strength(UTS),and elongation to failure(εf)are almost the identical for samples with ASTM standard size.Whilst,relatively lower YS and UTS values,except forεf,are observed for samples with a miniature size compared with that of ASTM standard samples.Theεf values of LMD-produced 316L SS samples show a more complex trend with sample size,and are afected by three key infuencing factors,namely,slimness ratio,cluster of pores,and occupancy location of lack of fusion defects.In general,theεf values exhibit a decreasing trend with the increase of slimness ratio.Microstructure characterization reveals that the LMD-produced 316L samples exhibited a high stress status at low angle grain boundaries,whilst its location changed to high angle grain boundaries after plastic deformation.The grain size refnement and austenite-to-martensite phase transformation occurred during plastic deformation might be responsible for the very high YS and UTS attained in this study.The experimental works carried out in this study is expected to provide a guideline for evaluating the mechanical properties of LMD-produced parts with complex structure,where critical parameter such as a certain slimness ratio has to be considered.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.11772344).
文摘Metal additive manufacturing(AM),as a disruptive technology in the feld of fabricating metallic parts,has shown its ability to design component with macrostructural complexity.However,some of these functionally complex structures typically contain a wide range of feature sizes,namely,the characteristic length of elements in AM-produced components can vary from millimeter to meter-scale.The requisite for controlling performance covers nearly six orders of magnitude,from the microstructure to macro scale structure.Understanding the mechanical variation with the feature size is of critical importance for topology optimization engineers to make required design decisions.In this work,laser metal deposition(LMD)is adopted to manufacture 316L stainless steel(SS)samples.To evaluate the efect of defects and specimen size on mechanical properties of LMD-produced samples,fve rectangular sample sizes which ranged from non-standard miniature size to ASTM standard sub-sized samples were machined from the block.Tensile test reveals that the mechanical properties including yield strength(YS),ultimate tensile strength(UTS),and elongation to failure(εf)are almost the identical for samples with ASTM standard size.Whilst,relatively lower YS and UTS values,except forεf,are observed for samples with a miniature size compared with that of ASTM standard samples.Theεf values of LMD-produced 316L SS samples show a more complex trend with sample size,and are afected by three key infuencing factors,namely,slimness ratio,cluster of pores,and occupancy location of lack of fusion defects.In general,theεf values exhibit a decreasing trend with the increase of slimness ratio.Microstructure characterization reveals that the LMD-produced 316L samples exhibited a high stress status at low angle grain boundaries,whilst its location changed to high angle grain boundaries after plastic deformation.The grain size refnement and austenite-to-martensite phase transformation occurred during plastic deformation might be responsible for the very high YS and UTS attained in this study.The experimental works carried out in this study is expected to provide a guideline for evaluating the mechanical properties of LMD-produced parts with complex structure,where critical parameter such as a certain slimness ratio has to be considered.
