With a high energy efficiency,low geometric limitation,and low cracking susceptivity to cracks,wire arc additive manufacturing(WAAM)has become an ideal substitute for casting in the manufacturing of load-bearing high ...With a high energy efficiency,low geometric limitation,and low cracking susceptivity to cracks,wire arc additive manufacturing(WAAM)has become an ideal substitute for casting in the manufacturing of load-bearing high strength aluminum components in aerospace industry.Recently,in scientific researches,the room temperature mechanical performance of additive manufactured high strength aluminum alloys has been continuously broken through,and proves these alloys can achieve comparable or even higher properties than the forged counterpart.Since the aluminum components for aerospace usage experience high-low temperature cycling due to the absence of atmosphere protection,the high temperature performances of additive manufactured high strength aluminum alloys are also important.However,few research focuses on that.A special 2319Ag Sc with 0.4 wt.%Ag and 0.2 wt.%Sc addition designed for high temperature application is deposited successfully via cold metal transfer(CMT)based on WAAM.The microstructures and high temperature tensile properties are investigated.The results show that the as-deposited 2319Ag Sc alloy presents an alternate distribution of columnar grains and equiaxed grains with no significant textures.Main second phases are Al_(2)Cu and Al3Sc,while co-growth of Al_(2)Cu and bulk Al_(3)Sc is found on the grain boundary.During manufacturing,nanoscale Al_(2)Cu can precipitate out from the matrix.Ag and Mg form nano-scaleΩphase on the Al_(2)Cu precipitates.At 260℃,average yield strengths in the horizontal direction and vertical direction are 87 MPa±2 MPa,87 MPa±4 MPa,while average ultimate tensile strengths are 140 MPa±7 MPa,141 MPa±11 MPa,and average elongations are 11.0%±2.5%,13.5%±3.0%.Anisotropy in different directions is weak.展开更多
Creep lives of high Cr ferritic heat resisting steel weldments decrease due to Type Ⅳ fracture, which occurs as a result of formation and growth of creep voids and cracks on grain boundaries in fine-grained heat affe...Creep lives of high Cr ferritic heat resisting steel weldments decrease due to Type Ⅳ fracture, which occurs as a result of formation and growth of creep voids and cracks on grain boundaries in fine-grained heat affected zone (HAZ). Because boron is considered to suppress the coarsening of grain boundary precipitates and growth of creep voids, we have investigated the effect of boron addition on the creep properties of 9Cr steel weldments. Four kinds of 9Cr3WSCoVNb steels with boron content varying from 4.7×10-5 to 1.8×10-4 and with nitrogen as low as 2.0×10-5 were prepared. The steel plates were welded by gas tungsten arc welding and crept at 923K. It was found that the microstructures of HAZ were quite different from those of conventional high Cr steels such as P91 and P92, namely the fine-grained HAZ did not exist in the present steel weldments. Boron addition also has the effect to suppress coarsening of grain boundary carbides in HAZ during creep. As a result of these phenomena, the welded joints of present steels showed no Type Ⅳ fractures and much better creep lives than those of conventional steels.展开更多
The effect of additives, such as CaO and V2O5 on the magnetic properties of high frequency MnZn power ferrite is studied by the conventional ceramic process. As a result, the grain boundary resistivity increases and t...The effect of additives, such as CaO and V2O5 on the magnetic properties of high frequency MnZn power ferrite is studied by the conventional ceramic process. As a result, the grain boundary resistivity increases and the power loss declines with the addition of CaO enriched at the grain boundary. By adding an optimum amount of V2O5 which acts indirectly via liquid phase formation and influences the microstructural development during sintering, the crystalline grain of ferrite was refined, the porosity decreases, the amount of grain boundary and the grain boundary resistivity increased, so the power loss is suppressed.展开更多
以丙烯酰胺(AM)、2-丙烯酰胺基-2-甲基丙磺酸(AMPS)、丙烯酸(AA)和二烯丙基二甲基氯化铵(DMDAAC)为聚合单体,过硫酸铵-亚硫酸氢钠为氧化还原引发体系,通过水溶液聚合得到一种新型抗盐、抗高温、强抑制钻井液降滤失剂SN-K。通过单因素实...以丙烯酰胺(AM)、2-丙烯酰胺基-2-甲基丙磺酸(AMPS)、丙烯酸(AA)和二烯丙基二甲基氯化铵(DMDAAC)为聚合单体,过硫酸铵-亚硫酸氢钠为氧化还原引发体系,通过水溶液聚合得到一种新型抗盐、抗高温、强抑制钻井液降滤失剂SN-K。通过单因素实验确定了最佳单体配比n(AM)∶n(AMPS)∶n(AA)∶n(DMDAAC)=1∶2∶2∶1,反应温度65℃,反应时间4 h,w(单体)=20%(以水溶液的总质量计,下同),w(引发剂)=0.5%(以单体总质量为基准,下同)。采用KOH调节聚合体系pH,引入强抑制性离子K+,并对SN-K进行性能评价。结果表明:在盐水钻井液中,w(SN-K)=3.0%(以钻井液总质量为基准,下同)时,经180℃高温老化16 h后,SN-K仍具有良好的降滤失效果,FLAPI=8.4 m L,没有添加SN-K的钻井液基浆的FLAPI=82.0 m L;泥页岩滚动回收实验表明:当w(SN-K)=1.0%时,岩屑相对岩心回收率(R*)为94.4%,远远超过KCl体系中w(KCl)=3.0%时的77.3%;利用SEM对添加SN-K的钻井液高温高压滤饼进行了微观表征,结果显示其具有致密的网架结构。展开更多
基金the National Natural Science Foundation of China(Grant No.U21B2080,52305351,52275324)the China Postdoctoral Science Foundation(Grant No.2023M730838)+1 种基金the Heilongjiang Provincial Postdoctoral Science Foundation(Grant No.LBH-Z22128)the Natural Science Foundation of Heilongjiang Province(Grant No.LH2023E039).
文摘With a high energy efficiency,low geometric limitation,and low cracking susceptivity to cracks,wire arc additive manufacturing(WAAM)has become an ideal substitute for casting in the manufacturing of load-bearing high strength aluminum components in aerospace industry.Recently,in scientific researches,the room temperature mechanical performance of additive manufactured high strength aluminum alloys has been continuously broken through,and proves these alloys can achieve comparable or even higher properties than the forged counterpart.Since the aluminum components for aerospace usage experience high-low temperature cycling due to the absence of atmosphere protection,the high temperature performances of additive manufactured high strength aluminum alloys are also important.However,few research focuses on that.A special 2319Ag Sc with 0.4 wt.%Ag and 0.2 wt.%Sc addition designed for high temperature application is deposited successfully via cold metal transfer(CMT)based on WAAM.The microstructures and high temperature tensile properties are investigated.The results show that the as-deposited 2319Ag Sc alloy presents an alternate distribution of columnar grains and equiaxed grains with no significant textures.Main second phases are Al_(2)Cu and Al3Sc,while co-growth of Al_(2)Cu and bulk Al_(3)Sc is found on the grain boundary.During manufacturing,nanoscale Al_(2)Cu can precipitate out from the matrix.Ag and Mg form nano-scaleΩphase on the Al_(2)Cu precipitates.At 260℃,average yield strengths in the horizontal direction and vertical direction are 87 MPa±2 MPa,87 MPa±4 MPa,while average ultimate tensile strengths are 140 MPa±7 MPa,141 MPa±11 MPa,and average elongations are 11.0%±2.5%,13.5%±3.0%.Anisotropy in different directions is weak.
文摘Creep lives of high Cr ferritic heat resisting steel weldments decrease due to Type Ⅳ fracture, which occurs as a result of formation and growth of creep voids and cracks on grain boundaries in fine-grained heat affected zone (HAZ). Because boron is considered to suppress the coarsening of grain boundary precipitates and growth of creep voids, we have investigated the effect of boron addition on the creep properties of 9Cr steel weldments. Four kinds of 9Cr3WSCoVNb steels with boron content varying from 4.7×10-5 to 1.8×10-4 and with nitrogen as low as 2.0×10-5 were prepared. The steel plates were welded by gas tungsten arc welding and crept at 923K. It was found that the microstructures of HAZ were quite different from those of conventional high Cr steels such as P91 and P92, namely the fine-grained HAZ did not exist in the present steel weldments. Boron addition also has the effect to suppress coarsening of grain boundary carbides in HAZ during creep. As a result of these phenomena, the welded joints of present steels showed no Type Ⅳ fractures and much better creep lives than those of conventional steels.
文摘The effect of additives, such as CaO and V2O5 on the magnetic properties of high frequency MnZn power ferrite is studied by the conventional ceramic process. As a result, the grain boundary resistivity increases and the power loss declines with the addition of CaO enriched at the grain boundary. By adding an optimum amount of V2O5 which acts indirectly via liquid phase formation and influences the microstructural development during sintering, the crystalline grain of ferrite was refined, the porosity decreases, the amount of grain boundary and the grain boundary resistivity increased, so the power loss is suppressed.
文摘以丙烯酰胺(AM)、2-丙烯酰胺基-2-甲基丙磺酸(AMPS)、丙烯酸(AA)和二烯丙基二甲基氯化铵(DMDAAC)为聚合单体,过硫酸铵-亚硫酸氢钠为氧化还原引发体系,通过水溶液聚合得到一种新型抗盐、抗高温、强抑制钻井液降滤失剂SN-K。通过单因素实验确定了最佳单体配比n(AM)∶n(AMPS)∶n(AA)∶n(DMDAAC)=1∶2∶2∶1,反应温度65℃,反应时间4 h,w(单体)=20%(以水溶液的总质量计,下同),w(引发剂)=0.5%(以单体总质量为基准,下同)。采用KOH调节聚合体系pH,引入强抑制性离子K+,并对SN-K进行性能评价。结果表明:在盐水钻井液中,w(SN-K)=3.0%(以钻井液总质量为基准,下同)时,经180℃高温老化16 h后,SN-K仍具有良好的降滤失效果,FLAPI=8.4 m L,没有添加SN-K的钻井液基浆的FLAPI=82.0 m L;泥页岩滚动回收实验表明:当w(SN-K)=1.0%时,岩屑相对岩心回收率(R*)为94.4%,远远超过KCl体系中w(KCl)=3.0%时的77.3%;利用SEM对添加SN-K的钻井液高温高压滤饼进行了微观表征,结果显示其具有致密的网架结构。
