利用声发射无损探伤技术实时监测三种类型超高性能混凝土(Ultra High Performance Concrete,简称UHPC)轴拉试验过程中内部损伤点的形成和演化过程,同时通过裂缝观测仪量测UHPC拉应变到达2000με时的缝宽。与低应变强化UHPC和应变软化U...利用声发射无损探伤技术实时监测三种类型超高性能混凝土(Ultra High Performance Concrete,简称UHPC)轴拉试验过程中内部损伤点的形成和演化过程,同时通过裂缝观测仪量测UHPC拉应变到达2000με时的缝宽。与低应变强化UHPC和应变软化UHPC相比,高应变强化UHPC具有高抗拉强度和"类金属"拉伸应变强化性能,在强化段区间内通过多点微裂纹均布开展的形式来平衡等量变形,表现出优异的裂缝宽度控制能力。气体渗透测试证明高应变强化UHPC抗气渗性能优异,且拉应变达到2000με后即刻卸载状态下的抗气渗性能仍要优于未受荷C50混凝土。基于高应变强化UHPC这些特性,将其应用于桥梁结构的高应力区或其他需要高抗裂性能的部位将是预应力混凝土之外的新方案,例如钢-UHPC轻型组合结构、斜拉桥的桥塔锚固区。展开更多
Three kinds of Al-Zn-Mg-Cu based alloys with 0.22%, 0.36%(Sc+Zr) (mass fraction, %), and without Sc, Zr addition were prepared by ingot metallurgy. By using optical microscopy, transmission electronic microscopy and s...Three kinds of Al-Zn-Mg-Cu based alloys with 0.22%, 0.36%(Sc+Zr) (mass fraction, %), and without Sc, Zr addition were prepared by ingot metallurgy. By using optical microscopy, transmission electronic microscopy and scanning electron microscopy, the effects of microalloying elements of Sc, Zr on the microstructure of super-high-strength Al-Zn-Mg-Cu alloys related to mechanical properties were investigated. The tensile properties and microstructures of the studied alloys under different heat treatment conditions were studied. The addition of minor Sc, Zr results in the formation of Al3(Sc,Zr) particles. These particles are highly effective in refining the microstructures, retarding recrystallization, pinning dislocations and subboundaries. The strength of Al-Zn-Mg-Cu alloys was greatly improved by simultaneously adding minor Sc, Zr, meanwhile the ductility of the studied alloys remains at a higher level. The 0.36%(Sc+Zr) alloys gain the optimal properties after 465 ℃/h solution and 120 ℃/24 h aging. The increment of strength is mainly due to strengthening of fine grain and substructure and precipitation of Al3(Sc, Zr) particles.展开更多
对T6I6时效处理的6061铝合金的拉伸性能、晶间腐蚀性能和电导率进行了测试,并采用OM和TEM对其组织进行了观察.结果表明,6061铝合金经180℃×8 h T6峰值时效后,虽然强度较高,但有严重晶间腐蚀倾向;T6I6预时效时间对拉伸性能影响不大...对T6I6时效处理的6061铝合金的拉伸性能、晶间腐蚀性能和电导率进行了测试,并采用OM和TEM对其组织进行了观察.结果表明,6061铝合金经180℃×8 h T6峰值时效后,虽然强度较高,但有严重晶间腐蚀倾向;T6I6预时效时间对拉伸性能影响不大,但中断时效温度和时间对其影响显著.由于较高的中断时效温度和较长的中断时间能获得高密度的晶内析出相和呈球状不连续分布的晶界析出相,因此,T6I6时效处理后的6061铝合金不仅能保持较高强度,同时还能显著提高晶间腐蚀抗力.经180℃×2 h+150℃×2160 h+180℃×8 h T6I6时效,合金抗拉强度和屈服强度分别为348.5和326.9 MPa,相对于T6状态,仅分别下降了2.1%和1.4%,腐蚀类型由T6状态的晶间腐蚀转变为均匀腐蚀,腐蚀深度约为30μm.展开更多
文摘利用声发射无损探伤技术实时监测三种类型超高性能混凝土(Ultra High Performance Concrete,简称UHPC)轴拉试验过程中内部损伤点的形成和演化过程,同时通过裂缝观测仪量测UHPC拉应变到达2000με时的缝宽。与低应变强化UHPC和应变软化UHPC相比,高应变强化UHPC具有高抗拉强度和"类金属"拉伸应变强化性能,在强化段区间内通过多点微裂纹均布开展的形式来平衡等量变形,表现出优异的裂缝宽度控制能力。气体渗透测试证明高应变强化UHPC抗气渗性能优异,且拉应变达到2000με后即刻卸载状态下的抗气渗性能仍要优于未受荷C50混凝土。基于高应变强化UHPC这些特性,将其应用于桥梁结构的高应力区或其他需要高抗裂性能的部位将是预应力混凝土之外的新方案,例如钢-UHPC轻型组合结构、斜拉桥的桥塔锚固区。
基金Project(2002AA305104) supported by the National High-Tech Research and Development Program of China
文摘Three kinds of Al-Zn-Mg-Cu based alloys with 0.22%, 0.36%(Sc+Zr) (mass fraction, %), and without Sc, Zr addition were prepared by ingot metallurgy. By using optical microscopy, transmission electronic microscopy and scanning electron microscopy, the effects of microalloying elements of Sc, Zr on the microstructure of super-high-strength Al-Zn-Mg-Cu alloys related to mechanical properties were investigated. The tensile properties and microstructures of the studied alloys under different heat treatment conditions were studied. The addition of minor Sc, Zr results in the formation of Al3(Sc,Zr) particles. These particles are highly effective in refining the microstructures, retarding recrystallization, pinning dislocations and subboundaries. The strength of Al-Zn-Mg-Cu alloys was greatly improved by simultaneously adding minor Sc, Zr, meanwhile the ductility of the studied alloys remains at a higher level. The 0.36%(Sc+Zr) alloys gain the optimal properties after 465 ℃/h solution and 120 ℃/24 h aging. The increment of strength is mainly due to strengthening of fine grain and substructure and precipitation of Al3(Sc, Zr) particles.
文摘对T6I6时效处理的6061铝合金的拉伸性能、晶间腐蚀性能和电导率进行了测试,并采用OM和TEM对其组织进行了观察.结果表明,6061铝合金经180℃×8 h T6峰值时效后,虽然强度较高,但有严重晶间腐蚀倾向;T6I6预时效时间对拉伸性能影响不大,但中断时效温度和时间对其影响显著.由于较高的中断时效温度和较长的中断时间能获得高密度的晶内析出相和呈球状不连续分布的晶界析出相,因此,T6I6时效处理后的6061铝合金不仅能保持较高强度,同时还能显著提高晶间腐蚀抗力.经180℃×2 h+150℃×2160 h+180℃×8 h T6I6时效,合金抗拉强度和屈服强度分别为348.5和326.9 MPa,相对于T6状态,仅分别下降了2.1%和1.4%,腐蚀类型由T6状态的晶间腐蚀转变为均匀腐蚀,腐蚀深度约为30μm.
