This study investigates the combustion characteristics of reactive aluminium alloys in combination with fluoropolymer oxidizers. Aluminium-magnesium(Al-Mg) and aluminium-titanium(Al-Ti) alloys were selected as metalli...This study investigates the combustion characteristics of reactive aluminium alloys in combination with fluoropolymer oxidizers. Aluminium-magnesium(Al-Mg) and aluminium-titanium(Al-Ti) alloys were selected as metallic fuels, while polyvinylidene fluoride(PVDF) was employed as the oxidizer. Composite samples were prepared using two methods: electrostatic spraying(ES) and physical mixing(PM). The ES method yielded samples with a PVDF-coated structure, whereas the PM method produced simple mixtures. The samples and their combustion products were characterized using scanning electron microscopy(SEM), X-ray diffraction(XRD), combustion experiments, and thermal analysis. The results indicate that compared to the PM samples, the ES-coated samples exhibited more effective dispersion of metallic particles, reduced particle agglomeration, increased combustion heat release temperature, decreased maximum flame area and height, and mitigated or eliminated explosive or micro-explosive phenomena during combustion, thereby achieving stable combustion. Additionally, the ES samples demonstrated a significant reduction in the particle size of condensed-phase products after combustion, alleviated sintering and agglomeration, decreased the formation of metal oxides, and minimized residual metallic fuel, allowing for the full release of combustion heat. Thermal analysis revealed that the coating structure of the ES samples lowered the activation energy for the reaction between the metallic fuel and PVDF, thereby enhancing the chemical reactivity.展开更多
Nb-Si-based in situ composites are receiving attention as a substitute for Ni-based alloys in aerospace,while poor toughness limits its application.In this work,the toughness of Nb_(4)FeSi-containing Nb-Si-based alloy...Nb-Si-based in situ composites are receiving attention as a substitute for Ni-based alloys in aerospace,while poor toughness limits its application.In this work,the toughness of Nb_(4)FeSi-containing Nb-Si-based alloys was improved by hot deformation.The different deformation behaviors of reinforcements from traditional alloys,including the eutectoid decomposition ofβ-Nb_(5)Si_(3),and the stacking faults(SFs)and reorientation-induced plasticity(RIP)effect of Nb_(4)FeSi,are revealed.During hot deformation,theβ-Nb_(5)Si_(3)phase undergoes the eutectoid decomposition to obtain theα-Nb_(5)Si_(3)and niobium-based solid solutions(Nbss)phases,whichα-Nb_(5)Si_(3)and Nbss satisfy the relationship{110}_(α)//{110}_(Nbss).The[110]SFs and lath-like reoriented variants are formed in the Nb_(4)FeSi phase,where the matrix and variants follow[001]_(m)//[111]v,(110)_(m)//(110)v.Furthermore,the interface between matrix and variant isΣ33c symmetrical tilt boundaries,manifested as(110)/60°.The fracture toughness of the deformed alloy reaches 18.31 MPa·m1/2 at 1300℃/0.005 s^(-1)/0.7,which is 49%higher than the initial alloy.展开更多
Al-Ti diffusion couples were made by embedded technology and treated at the temperature between the melting points of Al and Ti. The microstructure evolution and growth mechanism of the Al-Ti DRZ were investigated. Th...Al-Ti diffusion couples were made by embedded technology and treated at the temperature between the melting points of Al and Ti. The microstructure evolution and growth mechanism of the Al-Ti DRZ were investigated. The result shows that the DRZ, the mixture of TiAl3 and Al, grows layer by layer along their chemical equilibrium zone. In the course, the growth interface moves toward the aluminum side. TiAl3 is the only new phase which forms earliest in the course of heat-treatment. The growth mechanism of the DRZ changes after the phase transition of titanium. Before the phase transition of titanium, the growth of the DRZ is controlled by the dissolution speed of the titanium to the molten aluminum, while after the phase transition of titanium, the growth is controlled by the chemical reaction speed of Al and Ti atoms, and consequently, its growth rate is greatly increased.展开更多
基金National Natural Science Foundation of China (NSFC,Grant Nos.52176114 and 52306145)Natural Science Foundation of Jiangsu Province (Grant No.BK20230929)+2 种基金China Postdoctoral Science Foundation (Grant No.2024M764222)Fundamental Research Funds for the Central Universities (Grant No.30924010505)Jiangsu Funding Program for Excellent Postdoctoral Talent。
文摘This study investigates the combustion characteristics of reactive aluminium alloys in combination with fluoropolymer oxidizers. Aluminium-magnesium(Al-Mg) and aluminium-titanium(Al-Ti) alloys were selected as metallic fuels, while polyvinylidene fluoride(PVDF) was employed as the oxidizer. Composite samples were prepared using two methods: electrostatic spraying(ES) and physical mixing(PM). The ES method yielded samples with a PVDF-coated structure, whereas the PM method produced simple mixtures. The samples and their combustion products were characterized using scanning electron microscopy(SEM), X-ray diffraction(XRD), combustion experiments, and thermal analysis. The results indicate that compared to the PM samples, the ES-coated samples exhibited more effective dispersion of metallic particles, reduced particle agglomeration, increased combustion heat release temperature, decreased maximum flame area and height, and mitigated or eliminated explosive or micro-explosive phenomena during combustion, thereby achieving stable combustion. Additionally, the ES samples demonstrated a significant reduction in the particle size of condensed-phase products after combustion, alleviated sintering and agglomeration, decreased the formation of metal oxides, and minimized residual metallic fuel, allowing for the full release of combustion heat. Thermal analysis revealed that the coating structure of the ES samples lowered the activation energy for the reaction between the metallic fuel and PVDF, thereby enhancing the chemical reactivity.
基金supported by the National Natural Science Foundation of China(Nos.52425401 and 52374384)the Foundation of National Key Laboratory for Precision Hot Processing of Metals(No.JCKYS2021603C001)the Fundamental Research Funds for the Central Universities(No.2023FRFK06014).
文摘Nb-Si-based in situ composites are receiving attention as a substitute for Ni-based alloys in aerospace,while poor toughness limits its application.In this work,the toughness of Nb_(4)FeSi-containing Nb-Si-based alloys was improved by hot deformation.The different deformation behaviors of reinforcements from traditional alloys,including the eutectoid decomposition ofβ-Nb_(5)Si_(3),and the stacking faults(SFs)and reorientation-induced plasticity(RIP)effect of Nb_(4)FeSi,are revealed.During hot deformation,theβ-Nb_(5)Si_(3)phase undergoes the eutectoid decomposition to obtain theα-Nb_(5)Si_(3)and niobium-based solid solutions(Nbss)phases,whichα-Nb_(5)Si_(3)and Nbss satisfy the relationship{110}_(α)//{110}_(Nbss).The[110]SFs and lath-like reoriented variants are formed in the Nb_(4)FeSi phase,where the matrix and variants follow[001]_(m)//[111]v,(110)_(m)//(110)v.Furthermore,the interface between matrix and variant isΣ33c symmetrical tilt boundaries,manifested as(110)/60°.The fracture toughness of the deformed alloy reaches 18.31 MPa·m1/2 at 1300℃/0.005 s^(-1)/0.7,which is 49%higher than the initial alloy.
基金Project (ZR2011EL023) supported by the Natural Science Foundation of Shandong Province,ChinaProject (12CX04057A) supported by the Fundamental Research Funds for the Central Universities,China
文摘Al-Ti diffusion couples were made by embedded technology and treated at the temperature between the melting points of Al and Ti. The microstructure evolution and growth mechanism of the Al-Ti DRZ were investigated. The result shows that the DRZ, the mixture of TiAl3 and Al, grows layer by layer along their chemical equilibrium zone. In the course, the growth interface moves toward the aluminum side. TiAl3 is the only new phase which forms earliest in the course of heat-treatment. The growth mechanism of the DRZ changes after the phase transition of titanium. Before the phase transition of titanium, the growth of the DRZ is controlled by the dissolution speed of the titanium to the molten aluminum, while after the phase transition of titanium, the growth is controlled by the chemical reaction speed of Al and Ti atoms, and consequently, its growth rate is greatly increased.
