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采用激光熔化沉积方法制备了Ti6Al4V合金单墙体,研究了工艺参数对熔池尺寸稳定性、沉积层微观组织生长特性的影响。基于有限元模拟方法,计算了不同工艺条件下熔池的温度场及熔体的冷却速率。结果表明,在前几层的熔化沉积过程中,熔池尺寸会随基体散热条件的改变发生明显变化。对每层热量输入进行优化,可以准确控制熔池尺寸的稳定性。相比激光功率,扫描速度对沉积层定向生长特性及晶粒尺寸的影响更为显著,随着扫描速度的改变,沉积层组织很容易实现从柱状晶到等轴晶的改变。在本试验条件下,当熔池冷却速率高于135.3℃/s时,方可形成定向生长的柱状晶。
Ti6Al4V alloy single wall was prepared by laser melting deposition method. The influence of process parameters on the dimensional stability of molten pool and microstructure growth of the deposited layer was studied. Based on the finite element simulation method, the temperature field and the cooling rate of the melt under different process conditions were calculated. The results show that during the first few layers of melt deposition, the size of the weld pool changes significantly with the change of the substrate cooling conditions. Optimize heat input for each floor to accurately control bath size stability. Compared with the laser power, the effect of scanning speed on the directional growth characteristics and grain size of the deposited layer is more significant. With the change of scanning speed, the deposited layer can easily change from columnar to equiaxed. Under the experimental conditions, when the cooling rate of the molten pool is higher than 135.3 ℃ / s, the directional growth of columnar crystals can be formed.