Alloys with a hexagonal close-packed(HCP)lattice often suffer from intrinsic brittleness due to their in-sufficient number of slip systems,which limits their practical uses.In this paper,nevertheless,we show that rema...Alloys with a hexagonal close-packed(HCP)lattice often suffer from intrinsic brittleness due to their in-sufficient number of slip systems,which limits their practical uses.In this paper,nevertheless,we show that remarkably tensile ductility in HCP Hf-Zr-Ti medium entropy alloys(MEAs)was achieved,particu-larly in the MEAs with a higher content of Hf.Both first-principles calculation and experimental analyses reveal that addition of Hf increases basal I2 stacking fault energy and decreases prismatic stacking fault energy in these HCP MEAs,which promotes the source of pyramidal dislocations due to the facilitated cross slips of basal dislocations and eventually give rise to the observed large tensile ductility.Our current findings not only shed new insights into understanding deformation of HCP alloys,but also provide a basis for controlling alloying effects for developing novel HCP complex alloys with optimized properties.展开更多
Refractory high-entropy alloys have great potential to be utilized as high-temperature materials,and the repeatability and reproducibility of their mechanical properties are critical for practical applications.In this...Refractory high-entropy alloys have great potential to be utilized as high-temperature materials,and the repeatability and reproducibility of their mechanical properties are critical for practical applications.In this work,nevertheless,we found that the mechanical properties of the TiZrHfNb HEA greatly varied with the content of impurities in the samples even using high-purity raw materials.Specifically,the oxygen impurity is mainly responsible for the increment of the yield stress due to the strong interstitial hardening effect,whilst the ductility deterioration closely associates with the content of metalloid elements B,C,and Si.Our analysis reveals that the metalloid elements not only tend to segregate at grain boundaries but also enhance the aggregation of Zr and Ti.Such co-segregation induced the formation of strong(Zr,Ti)-metalloid bonds,resulting in grain boundary embrittlement and brittle fracture.Our current work demonstrates that the impurity contents in refractory HEAs need to be strictly controlled during production in order to improve their stability of mechanical performance.展开更多
基金supported by the National Natural Science Foundation of China(Nos.11790293,51871016,51671021,51971017,52122408,52071023,51901013)the Funds for Creative Research Groups of China(51921001)+3 种基金111 Project(BP0719004)Program for Changjiang Scholars and Innovative Research Team in University of China(IRT_14R05)financial support from the Fundamental Research Funds for the Central Universities of China(No.FRF-TP-18-004C1,No.FRF-BD-19-002B,respectively)financial support from Projects of SKLAMM-USTB(2019Z-01,2018-Z01,2022Z-09).
文摘Alloys with a hexagonal close-packed(HCP)lattice often suffer from intrinsic brittleness due to their in-sufficient number of slip systems,which limits their practical uses.In this paper,nevertheless,we show that remarkably tensile ductility in HCP Hf-Zr-Ti medium entropy alloys(MEAs)was achieved,particu-larly in the MEAs with a higher content of Hf.Both first-principles calculation and experimental analyses reveal that addition of Hf increases basal I2 stacking fault energy and decreases prismatic stacking fault energy in these HCP MEAs,which promotes the source of pyramidal dislocations due to the facilitated cross slips of basal dislocations and eventually give rise to the observed large tensile ductility.Our current findings not only shed new insights into understanding deformation of HCP alloys,but also provide a basis for controlling alloying effects for developing novel HCP complex alloys with optimized properties.
基金This research was financially supported by the National Natural Science Foundation of China(Nos.11790293,52225103,51871016,52271003,52071023,52122408,and 52225103)the Funds for Creative Research Groups of China(No.51921001)+2 种基金Project of International Cooperation and Exchanges NSFC(No.52061135207,51961160729)National Key Research and Development Program of China(2022YFB4602101)Joint Project of NSFC(No.U20B2025111).
文摘Refractory high-entropy alloys have great potential to be utilized as high-temperature materials,and the repeatability and reproducibility of their mechanical properties are critical for practical applications.In this work,nevertheless,we found that the mechanical properties of the TiZrHfNb HEA greatly varied with the content of impurities in the samples even using high-purity raw materials.Specifically,the oxygen impurity is mainly responsible for the increment of the yield stress due to the strong interstitial hardening effect,whilst the ductility deterioration closely associates with the content of metalloid elements B,C,and Si.Our analysis reveals that the metalloid elements not only tend to segregate at grain boundaries but also enhance the aggregation of Zr and Ti.Such co-segregation induced the formation of strong(Zr,Ti)-metalloid bonds,resulting in grain boundary embrittlement and brittle fracture.Our current work demonstrates that the impurity contents in refractory HEAs need to be strictly controlled during production in order to improve their stability of mechanical performance.
