选区激光熔化Inconel 718合金的熔池形态与组织

通过不同扫描速度和扫描方式的选区激光熔化(SLM)技术制备了Inconel 718合金,研究了工艺参数对熔池的形态、凝固组织、晶粒大小和晶粒取向的影响。结果表明,随着扫描速度增加,熔池的深度与宽度的比值增大,曲率增大;而扫描速度为1 450mm/s时,采用单向扫描比十字交叉扫描时深宽比值更大。在熔池内,凝固组织由熔池底部的胞晶向熔池侧面的胞枝晶转变。晶粒以<001>方向择优生长,其晶粒间的取向差角以小角度(<15°)为主。当十字交叉扫描时,随着扫描速度增加,小角度取向差角的分布分数增加。当速度一定、采用十字交叉扫描时,小角度的取向差角占比为62.57%,而采用单向扫描时为47.69%。

Molten-pool Morphology and Microstructure of Selective Laser Melted Inconel 718 Alloy

The Inconel 718 alloy was fabricated by selective laser melting with different scanning speeds and modes.The effects of process parameters on molten-pool morphology,solidification structure,grain growth and grain orientation were investigated.The results indicate that the depth-width ratio of the molten-pool is increased and the curvature is decreased with the increase of the scanning rate,while the ratio with the single-direction scanning is greater than that with the decussation scanning at 1 450 mm/s.In the molten pool,the solidified structure is converted from the cell crystal at the bottom to the cell dendrite on the side of the molten pool.The grains are grown along the preferred orientation of<001>direction,and the misorientation is dominated by small-angle misorientation(<15°).The fraction of small-angle misorientation is increased with the scanning rate increase under the decussation scanning mode.When scanning rate is constant,the fraction of the small-angle misorientation is 62.57% under the decussation scanning mode,while that under single-direction scanning mode is 47.69%.