7055铝合金粉末的氩气低压雾化技术

摘要

In order to improve the energy transfer efficiency and manufacturability, a Laval-type atomizer was designed and atomization experiments were conducted to evaluate the atomization capability of the designed atomizer. The argon atomization results for 7055Al alloy show that when the atomization pressures P0=0.4, 0.6 and 0.8 MPa, the corresponding mass median diameter d50 of atomized powders are 63.5, 57.1 and 43.4μm, respectively. Comparing with conventional close coupled atomizer, the designed Laval-type atomizer can obtain supersonic gas flow at lower gas pressure, and has better low-pressure atomization capability. During the cooling progress of atomized droplets, plenty of fine dendritic crystals with the size ranging from 0.5 to 2.5 μm formed, and the measured dendrite arm spacing λ and powder size d have the following relationship:λ=0.192 3d0.547. The calculated cooling rate of atomized droplets decreases as the diameter increases, and the cooling rate of atomized droplets can reach 104~105 K/s.%将传统环缝喷嘴结构改造为Laval型出气口，以实现低压高效雾化制粉，利用该喷嘴进行7055铝合金氩气低压雾化制粉实验，对Laval型喷嘴的雾化能力、熔滴凝固特性与粉末微观组织进行研究。结果表明：与传统紧耦合喷嘴相比，Laval 型喷嘴具有更好的低压雾化能力，在较低雾化压力下即可获得超音速雾化气流，雾化压力为0.4，0.6和0.8 MPa时雾化粉末的质量中径d50分别为63.5，57.1和43.4μm，大部分合金粉末呈球形或类球形；雾化熔滴凝固过程中产生大量尺寸在0.5~2.5μm范围内的细小枝晶组织，枝晶间距λ与粉末粒径d近似满足如下关系：λ=0.1923 d 0.547；雾化粉末具有快速凝固特性，冷却速率达到104~105 K/s，随熔滴粒径增大而减小。