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采用按需喷射方法制备不同粒径的Cu-6%Sn合金粉末,测量不同粒径条件下的二次枝晶间距,并且推导出半经验公式,建立二次枝晶间距与液滴冷却速率之间的数学关系,并利用光学显微镜和背散射电子显微镜观察液滴组织形貌。结果表明:枝晶特征取决于凝固速率、冷却介质以及飞行距离;液滴温度处于液相线与固相线之间,当液滴彼此发生碰撞时,由于碰撞引起热传导率提高,经过数学模型推导,发生碰撞的液滴冷却速率超过4×10~4 K/s,枝晶组织和晶粒明显细化。由于液滴内部温度梯度作用,枝晶沿碰撞方向生长。
The Cu-6% Sn alloy powders with different particle sizes were prepared by drop-on-demand method. The secondary dendrite spacing under different particle sizes was measured and the semi-empirical formula was deduced to establish the secondary dendrite spacing and the droplet cooling rate Between the mathematical relationship, and the use of optical microscopy and backscattered electron microscopy observation of droplet morphology. The results show that the characteristics of dendrite depend on the solidification rate, the cooling medium and the flight distance. The droplet temperature lies between the liquidus and the solidus. When the droplets collide with each other, the thermal conductivity increases due to the collision. , The collisional droplet cooling rate exceeds 4 × 10 ~ 4 K / s, the dendrite structure and grain refinement significantly. Dendrites grow along the collision direction due to the temperature gradient inside the droplet.