通过原位电化学充氢方法(电流密度0、2和4 m A/cm^(2))研究了45Cr Ni MoVA钢的低周疲劳行为及其断裂机制。结果表明:该材料在循环加载过程中呈现出应变幅值依赖的非饱和循环软化现象和non-Masing特性,其中non-Masing行为在低应变幅条件...通过原位电化学充氢方法(电流密度0、2和4 m A/cm^(2))研究了45Cr Ni MoVA钢的低周疲劳行为及其断裂机制。结果表明:该材料在循环加载过程中呈现出应变幅值依赖的非饱和循环软化现象和non-Masing特性,其中non-Masing行为在低应变幅条件下表现尤为显著。尽管充氢电流密度对材料的循环滞回行为无明显影响,但材料的抗疲劳性能却明显依赖于充氢电流密度大小和应变幅值。随着充氢电流密度的增加,材料内部氢浓度增高,导致疲劳损伤加速累积,且高应变幅工况下氢致寿命劣化效应显著高于低应变幅工况。扫描电镜(SEM)断口分析表明,充氢显著改变了材料的疲劳断裂机制:未充氢试样呈现典型的表面裂纹萌生与韧性断裂特征;而随充氢电流密度和应变幅值的提高,充氢试样的裂纹萌生位置由试样表面向内部缺陷转移,且脆性特征(准解理与沿晶分离形态)显著增强。充氢试样裂纹萌生区与扩展区均呈现韧窝、准解理和沿晶分离形态并存的混合断裂特征。展开更多
The effects of channel segregation on the macro-and micro-scale chemical composition,microstructure,hardness,and tensile deformation behavior of Ti45Nb wires were investigated.The results show that wires with severe c...The effects of channel segregation on the macro-and micro-scale chemical composition,microstructure,hardness,and tensile deformation behavior of Ti45Nb wires were investigated.The results show that wires with severe channel segregation exhibit a macroscopic chemical composition identical to those without segregation,and 3D X-ray imaging result also reveals no abnormalities.After annealing,both types of wires exhibit an equiaxed single-phase microstructure with comparable grain sizes,suggesting that channel segregation has negligible influence on the macroscopic composition and grain size.Metallographic examination reveals that channel segregation manifests as spot-like features in the transverse section and band-like structures in the longitudinal section.EDS analysis identifies these regions as Ti-enriched segregations,with a Ti content higher than that of the surrounding matrix by approximately 4.42wt%.Compared to segregation-free wires,those containing extensive channel segregation demonstrate a 15.5%increase in ultimate tensile strength and a 12.3%increase in yield strength,but suffer a reduction in elongation and reduction of area by 19.8%and 18.9%,respectively.Furthermore,the mechanical properties of wires with segregation show significant fluctuations.Fractographic analysis reveals a larger fracture surface area in segregated wires.Severe dislocation pile-ups occur at the interfaces of these segregated regions,initiating microcrack nucleation.This promotes rapid crack propagation of the Ti45Nb wire,leading to a significant decrease in plasticity and reduction of area.展开更多
文摘通过原位电化学充氢方法(电流密度0、2和4 m A/cm^(2))研究了45Cr Ni MoVA钢的低周疲劳行为及其断裂机制。结果表明:该材料在循环加载过程中呈现出应变幅值依赖的非饱和循环软化现象和non-Masing特性,其中non-Masing行为在低应变幅条件下表现尤为显著。尽管充氢电流密度对材料的循环滞回行为无明显影响,但材料的抗疲劳性能却明显依赖于充氢电流密度大小和应变幅值。随着充氢电流密度的增加,材料内部氢浓度增高,导致疲劳损伤加速累积,且高应变幅工况下氢致寿命劣化效应显著高于低应变幅工况。扫描电镜(SEM)断口分析表明,充氢显著改变了材料的疲劳断裂机制:未充氢试样呈现典型的表面裂纹萌生与韧性断裂特征;而随充氢电流密度和应变幅值的提高,充氢试样的裂纹萌生位置由试样表面向内部缺陷转移,且脆性特征(准解理与沿晶分离形态)显著增强。充氢试样裂纹萌生区与扩展区均呈现韧窝、准解理和沿晶分离形态并存的混合断裂特征。
基金National Natural Science Foundation of China(U24A2038)。
文摘The effects of channel segregation on the macro-and micro-scale chemical composition,microstructure,hardness,and tensile deformation behavior of Ti45Nb wires were investigated.The results show that wires with severe channel segregation exhibit a macroscopic chemical composition identical to those without segregation,and 3D X-ray imaging result also reveals no abnormalities.After annealing,both types of wires exhibit an equiaxed single-phase microstructure with comparable grain sizes,suggesting that channel segregation has negligible influence on the macroscopic composition and grain size.Metallographic examination reveals that channel segregation manifests as spot-like features in the transverse section and band-like structures in the longitudinal section.EDS analysis identifies these regions as Ti-enriched segregations,with a Ti content higher than that of the surrounding matrix by approximately 4.42wt%.Compared to segregation-free wires,those containing extensive channel segregation demonstrate a 15.5%increase in ultimate tensile strength and a 12.3%increase in yield strength,but suffer a reduction in elongation and reduction of area by 19.8%and 18.9%,respectively.Furthermore,the mechanical properties of wires with segregation show significant fluctuations.Fractographic analysis reveals a larger fracture surface area in segregated wires.Severe dislocation pile-ups occur at the interfaces of these segregated regions,initiating microcrack nucleation.This promotes rapid crack propagation of the Ti45Nb wire,leading to a significant decrease in plasticity and reduction of area.
