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Journal of Zhejiang University-SCIENCE A

, Volume 19, Issue 2, pp 111–121 | Cite as

Influence of substrate surface morphology on wetting behavior of tracks during selective laser melting of aluminum-based alloys

  • Jie Liu
  • Dong-dong Gu
  • Hong-yu Chen
  • Dong-hua Dai
  • Han Zhang
Article
  • 111 Downloads

Abstract

AlSi12 samples were prepared by selective laser melting (SLM) under different processing conditions in order to obtain different top surface morphologies, where single tracks were produced using a fixed processing parameter to reveal the mechanism of the single track on different morphologies. The results show that the morphologies of single tracks changed with roughness of the top surface (Top Ra) of SLM parts, reflected in the variation of wetting angles on the surface processed previously as well as in dimensions of height, width, and depth at the cross-section of each single track. These changes were mainly caused by different wettability and flow behavior of the molten metal under various solidification environments of the single track during SLM. A poor solidification environment in which numerous balls existed limited an effective wetting behavior of molten metal on a previously processed surface of a SLM sample because of an increasing solid-liquid contact area, thus causing dramatical instability of the melt pool and attendant inferior processability of the single track. Meanwhile, under the action of surface tension, the molten metal had a high tendency to transfer into a pore near the single track to form an extending track or flow toward an upper region of melt to form a balling track, hence showing various morphologies of single tracks. This study proposes a theory of the solidification mechanism of single track on the non-ideal surface to provide a better understanding of the SLM processing of Al-Si alloy.

Key words

Selective laser melting (SLM) AlSi12 Surface morphology Single track 

选区激光熔化铝合金基底表面形貌对轨道润湿行为的影响

概要

目的

研究选区激光熔化(SLM)过程中形貌差异较大的块体表面单道成形工艺性,分析单道的润湿行为,为进一步揭示SLM 加工过程中熔化轨迹的凝固行为提供理论基础。

创新点

1. 系统研究在不同加工参数下形成的不同表面形貌的块体上加工同一参数的单道;2. 基于熔体流动理论,分析在SLM 加工过程中已加工层存在的大量的热积累以及粗糙的成形表面对单道的润湿行为的影响。

方法

1. 对在不同形貌的块体上形成的单道进行分析,将单道形貌分为4 种典型类型(图4)。2. 通过分析单道横截面的几何尺寸(图5 和6),研究表面形貌对单道成形工艺性的影响。3. 基于Wenzel方程(公式(3))分析熔体在粗糙表面的润湿行为并基于Navier-Stokes 方程(公式(12))和Marangoni 方程(公式(13))分析熔体流动行为。

结论

1. 块体表面光滑、平整时,粉末在表面铺展均匀、熔化充分、润湿性好,有利于形成连续、规则的单道。2. 单道附近的块体表面存在较大孔隙时,孔隙中会积累一定量的粉末。熔融金属的重力和表面张力共同驱使液体向孔隙流动,单道出现扩展效应:润湿角明显减小,熔池宽度和深度增加。3. 块体表面球化颗粒及飞溅物增多时,表面凹凸不平,单道处熔化的粉末量减少,对基板的润湿性较差,熔池不稳定,导致单道出现颈缩。4. 块体表面存在大量球化颗粒和飞溅物时,单道附近团聚的铝合金球化颗粒极易被氧化,氧化膜使得颗粒表面光滑,从而难以被熔融金属润湿。此外,熔融金属的较大的温度梯度对熔体流动方向也有显著影响,易诱导单道出现球化效应。

关键词

选区激光熔化(SLM) AlSi12 表面形貌 单道 

CLC number

TN249 

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Copyright information

© Zhejiang University and Springer-Verlag GmbH Germany, part of Springer Nature 2018

Authors and Affiliations

  1. 1.College of Materials Science and TechnologyNanjing University of Aeronautics and AstronauticsNanjingChina
  2. 2.Jiangsu Provincial Engineering Laboratory for Laser Additive Manufacturing of High-Performance Metallic ComponentsNanjing University of Aeronautics and AstronauticsNanjingChina

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