The spheroidization of the Widmanstätten structure through thermo-mechanical processes,leading to the formation of fine recrystallized and sub-grain structures,is crucial for achieving a balance between strength ...The spheroidization of the Widmanstätten structure through thermo-mechanical processes,leading to the formation of fine recrystallized and sub-grain structures,is crucial for achieving a balance between strength and plasticity.This study systematically examined the spheroidization mechanism of the Widmanstätten structure in Ti-25Zr-4Al-1.5Mn(wt.%,TiZrAlMn)alloy under varying rolling temperatures and its influence on microstructure and mechanical properties.After rolling at 900℃,the specimen exhibited a mixed morphology of Widmanstätten and Basket-weave structures,with a high yield strength of approximately 1038 MPa but low plasticity(∼5.2%).While the rolling temperature was reduced to 850℃,the specimen exhibited refined prior-β grains,discontinuous grain boundaries and a small amount of equiaxed α grains,which collectively enhanced plasticity(∼12.4%)while preserving yield strength.As the rolling temperature further decreased,the dynamic recrystallization mechanism shifted from the discontinuous dynamic recrystallization(DDRX)to continuous dynamic recrystallization(CDRX).Specimens rolled at 800℃ and 750℃ showed excellent strength-plasticity synergy,with yield strengths of 1070 MPa and 1110 MPa,respectively,and total elongations of 15%and 18%,respectively.The enhanced yield strength is attributed to both fine-grain and sub-grain strengthening.Furthermore,the lower degree of recrystallization in the 750-AC specimen preserved a relatively high dislocation density,offering additional strengthening.The favorable plasticity results from a combination of equiaxedαgrains,“soft”barrier sub-grains,and a small number of twins.Additionally,the 750-AC specimen retained 6.4%of the fine β grains and the weak basal texture.These characteristics contribute to the enhanced plasticity.Therefore,750℃is the optimal rolling temperature for achieving the best strength-plasticity synergy in the hot-rolled TiZrAlMn alloy.These findings demonstrate that selecting the appropriate temperature during thermomechanical processing to optimize recrystallized grains and sub-grain content ensures excellent plasticity at high yield strength.This offers valuable guidance for developing near-α Ti alloys with superior mechanical properties.展开更多
基金financially supported by the National Natural Science Foundation of China(Nos.52125405,52127808,52071278,U22A20108 and 52471148)the Science Research Project of Hebei Education Department(No.KJZX202201)+2 种基金Natural Science Foundation of Hebei Province(No.242Q9906Z/E2021402002)Basic Research Project of Shijiazhuang City for Universities in Hebei Province(No.241791027A)the Hebei Provincial Department of Education Funding Project for Cultivating Innovative Ability of Graduate Students(Grant no.CXZZBS2025057/CXZZBS2025056).
文摘The spheroidization of the Widmanstätten structure through thermo-mechanical processes,leading to the formation of fine recrystallized and sub-grain structures,is crucial for achieving a balance between strength and plasticity.This study systematically examined the spheroidization mechanism of the Widmanstätten structure in Ti-25Zr-4Al-1.5Mn(wt.%,TiZrAlMn)alloy under varying rolling temperatures and its influence on microstructure and mechanical properties.After rolling at 900℃,the specimen exhibited a mixed morphology of Widmanstätten and Basket-weave structures,with a high yield strength of approximately 1038 MPa but low plasticity(∼5.2%).While the rolling temperature was reduced to 850℃,the specimen exhibited refined prior-β grains,discontinuous grain boundaries and a small amount of equiaxed α grains,which collectively enhanced plasticity(∼12.4%)while preserving yield strength.As the rolling temperature further decreased,the dynamic recrystallization mechanism shifted from the discontinuous dynamic recrystallization(DDRX)to continuous dynamic recrystallization(CDRX).Specimens rolled at 800℃ and 750℃ showed excellent strength-plasticity synergy,with yield strengths of 1070 MPa and 1110 MPa,respectively,and total elongations of 15%and 18%,respectively.The enhanced yield strength is attributed to both fine-grain and sub-grain strengthening.Furthermore,the lower degree of recrystallization in the 750-AC specimen preserved a relatively high dislocation density,offering additional strengthening.The favorable plasticity results from a combination of equiaxedαgrains,“soft”barrier sub-grains,and a small number of twins.Additionally,the 750-AC specimen retained 6.4%of the fine β grains and the weak basal texture.These characteristics contribute to the enhanced plasticity.Therefore,750℃is the optimal rolling temperature for achieving the best strength-plasticity synergy in the hot-rolled TiZrAlMn alloy.These findings demonstrate that selecting the appropriate temperature during thermomechanical processing to optimize recrystallized grains and sub-grain content ensures excellent plasticity at high yield strength.This offers valuable guidance for developing near-α Ti alloys with superior mechanical properties.
