颗粒尺寸对微米级铝粉动态响应的影响

Effect of grain size on dynamic response of micron aluminum powder

为得到颗粒尺寸对铝粉动态压缩响应的影响规律,基于分离式霍普金森压杆对3种不同尺寸颗粒的铝粉进行了不同应变率的加载,并采用红外测温系统测量了冲击压缩过程中铝粉试样的表面温度。应力应变结果表明:不同尺寸颗粒的铝粉对应变率的敏感程度不同,大颗粒试样对应变率效应不敏感,小颗粒试样的应变率效应明显。对比结果发现:粉体中颗粒越容易发生重排,加载速率对其影响就越大。加载试验后使用扫描电镜观察断口界面处的颗粒变形特点,发现颗粒较小的试样中颗粒变形较均匀,说明此试样受力相对均匀。红外测温结果表明,即使试样的加载历程相同,不同尺寸颗粒试样的温度变化不同;由颗粒间摩擦产生的内能沉积在颗粒表层,颗粒内外温度分布不均匀导致试样温度不同。

In order to understand the effect of particle size on the dynamic compression response of Al powder,the Al powder with three different particle sizes was loaded with different strain rates based on the split Hopkinson pressure bar,and the surface temperature of Al powder samples during impact compression was measured by infrared temperature measurement system.The stress-strain results show that the sensitivity of Al powder with different size particles to strain rate is different.The strain rate effect of large particle sample is not sensitive,and the strain rate effect of small particle sample is relatively obvious.The comparison results show that the strain rate effect of powder is related to particle rearrangement.The more easily the particles are to rearrange,the greater the effect of loading rate on it.Scanning electron microscopy was used to observe particle deformation characteristics at the fracture interface after the loading test.It was found that particle deformation of the sample with smaller particles was relatively uniform,indicating that the specimen was subjected to relatively uniform stress.The infrared temperature measurement results show that the temperature changes of samples with different size particles are different even though the loading process is the same.It is inferred from the analysis results that the internal energy generated by the friction between particles is deposited on the surface of particles,and the temperature distribution inside and outside the particles is not uniform.This leads to the different temperature of samples.