采用数值模拟的方法对TiAl合金粉末的射频(radio frequency)等离子体球化过程进行研究,分析速度场和温度场对不同粒径TiAl合金粉末的运动轨迹及质量变化的影响.结果表明:粉体颗粒在等离子体的高温作用下温度急剧升高,表面蒸发导致粒径降低,太小的颗粒很快蒸发消失掉;在冷却塔下端,不同粒径颗粒的运动轨迹存在较大差异,小颗粒倾向于随气流进入气流出口,大颗粒落到冷却塔底部被收集;增大气流量会提高球化系统中的气流速度,导致在气流出口能被气流带走的颗粒粒径变大,收粉率降低;模拟得到TiAl合金粉末球化后的粉末粒径分布、平均粒径及收粉率等参数与实验结果比较接近,模型能够较好地符合实际球化过程.
A numerical simulation method was used to study the radio frequency plasma spheroidization process of TiAl alloy powder.The effects of velocity field and temperature field on the motion trajectory and mass change of TiAl alloy powder with different particle size were analyzed.The results show that the temperature of powder particles increases rapidly under high temperature plasma,surface evaporation cause the reduction of particle size,and particles with small size tend to evaporate quickly.The motion trajectory of particles with different sizes in the lower end of the cooling tube is different obviously,small particles tend to enter the air outlet,while the larger particles are easy to fall down to the bottom of the cooling tube to be collected.Increasing air flow rate can improve the velocity of air flow in the spheroidizing system,causing larger particles to be taken away by the air,resulting in yield reduction.The simulation results of TiAl alloy powder spheroidization are close to the experimental results refer to parameters such as powder size distribution,average particle size and powder yield,and the model is in good accordance with the actual process of the spheroidization.
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