Influence of Particle Size of Aluminum Powder and Molding Pressure on Impact-Initiation of Al/PTFE
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摘要: 采用模压烧结法制备了不同成型压强下铝粉粒径分别为10、30和200
${\text{μ}}{\rm{m}}$ 的Al/PTFE试件,基于分离式霍普金森压杆(SHPB)试验装置进行冲击引发试验,试验过程中通过高速摄影装置记录活性材料的反应情况。试验结果表明:随着成型压强增大,试件的冲击反应速度阈值均呈现先增大后减小的趋势。铝粉粒径为10和30${\text{μ}}{\rm{m}}$ 时,较高成型压强的试件能够于点火延迟时间1000~1100${\text{μ}}{\rm{s}}$ 处发生反应,使试件冲击反应速度阈值骤降;铝粉粒径为200${\text{μ}}{\rm{m}}$ 时,活性材料点火延迟时间均在600${\text{μ}}{\rm{s}}$ 附近。在相同成型压强下,试件的冲击反应速度阈值随铝粉粒径增大而升高。活性材料的冲击点火反应与材料的微观缺陷、应力波在SHPB装置中的传播、应力脉冲幅值以及材料的破坏过程等因素相关。Abstract: Aluminum-polytetrafluoroethylene (Al/PTFE) specimens with different aluminum particle sizes of 10, 30 and 200${\text{μ}}{\rm{m}}$ and different molding pressures were prepared by compression molding and sintering. The impact-initiation test was carried out with split Hopkinson pressure bar (SHPB), and the reaction of the reactive materials was recorded by a high-speed photography device. It shows that with the increase of molding pressure, the speed threshold of impact-initiation of the specimen increases and then decreases. When the particle sizes of aluminum powder is around 10${\text{μ}}{\rm{m}}$ or 30${\text{μ}}{\rm{m}}$ , specimens with higher molding pressure can react with ignition delay time of 1000–1100${\text{μ}}{\rm{s}}$ , causing a sudden drawdown of the speed threshold of impact-initiation; for the specimens with 200${\text{μ}}{\rm{m}}$ aluminum powder, the ignition delay time stays around 600${\text{μ}}{\rm{s}}$ . The speed threshold of impact-initiation raises as the particle size of aluminum increases, under the same molding pressure. The impact ignition of the reactive material is related to the microscopic defects, the propagation of the stress wave in the SHPB device, the amplitude of the stress pulse and the destruction process of the material. -
表 1 不同成型压强下Al/PTFE试件的孔隙率
Table 1. Porosities of Al/PTFE reactive materials prepared under different molding pressures
Molding pressure/MPa Porosities of Al/PTFE/% 10 ${\text{μ}}{\rm{m}}$ Al particle 30 ${\text{μ}}{\rm{m}}$ Al particle 200 ${\text{μ}}{\rm{m}}$ Al particle 30 4.9 4.8 3.8 50 4.0 3.6 3.2 80 3.1 2.9 2.5 100 2.5 2.4 1.4 120 2.3 1.9 1.2 -
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