Recent studies have indicated that precipitation-strengthened high-entropy alloys(HEAs)show superior mechanical performance and have been successfully fabricated by additive manufacturing.However,the lack of fatigue a...Recent studies have indicated that precipitation-strengthened high-entropy alloys(HEAs)show superior mechanical performance and have been successfully fabricated by additive manufacturing.However,the lack of fatigue and fracture research has limited the engineering applications of additive manufacturing HEAs.This work explored a dual precipitation-strengthened(FeCoNi)_(86)Al_(7)Ti_(7) HEA with excellent tensile and fatigue strength,prepared through selective laser melting and heat treatment.Compared with the as-built samples,the tensile properties and fatigue endurance limit improved through aging by 48.7%and 30%,respectively.The strengthening mechanism and enhanced fatigue performance were clarified in detail.The improvement in fatigue strength was attributed to the improved resistance of the L1_(2) and L2_(1) precipitates.During deformation,the dislocation shear coherent L1_(2) precipitates reduced slip band energy and inhibited slip band expansion,while the L2_(1) particles acted as obstructions for further slip band propagation,severely limiting the rapid formation and propagation of crack growth.In-situ TEM cyclic tensile-tensile testing also clarified the fatigue crack growth behavior,demonstrating that crack deflection due to L2_(1) precipitate obstruction slowed down the crack growth rate and efficiently promoted the closure of the microcrack tips.This work offers im plications for a new strategy to develop additive manufacturing HEAs.展开更多
基金financially supported by the National Natural Sci-ence Foundation of China(Nos.51971123 and 51925103)the In-novation Program of Shanghai Municipal Education Commission(No.2021-01-07-00-09-E00114)+3 种基金the Program 173(No.2020-JCIQ-ZD-186-01)the Key Program of Science and Technology of Yun nan Province(No.202002AB080001-2)the 111 Project(No.D16002)the Space Utilization System of China Manned Space Engineer-ing(No.KJZ-YY-NCL08)。
文摘Recent studies have indicated that precipitation-strengthened high-entropy alloys(HEAs)show superior mechanical performance and have been successfully fabricated by additive manufacturing.However,the lack of fatigue and fracture research has limited the engineering applications of additive manufacturing HEAs.This work explored a dual precipitation-strengthened(FeCoNi)_(86)Al_(7)Ti_(7) HEA with excellent tensile and fatigue strength,prepared through selective laser melting and heat treatment.Compared with the as-built samples,the tensile properties and fatigue endurance limit improved through aging by 48.7%and 30%,respectively.The strengthening mechanism and enhanced fatigue performance were clarified in detail.The improvement in fatigue strength was attributed to the improved resistance of the L1_(2) and L2_(1) precipitates.During deformation,the dislocation shear coherent L1_(2) precipitates reduced slip band energy and inhibited slip band expansion,while the L2_(1) particles acted as obstructions for further slip band propagation,severely limiting the rapid formation and propagation of crack growth.In-situ TEM cyclic tensile-tensile testing also clarified the fatigue crack growth behavior,demonstrating that crack deflection due to L2_(1) precipitate obstruction slowed down the crack growth rate and efficiently promoted the closure of the microcrack tips.This work offers im plications for a new strategy to develop additive manufacturing HEAs.
