Full Text:   <791>

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CLC number: TN249

On-line Access: 2018-02-05

Received: 2017-11-06

Revision Accepted: 2018-01-10

Crosschecked: 2018-01-16

Cited: 0

Clicked: 1122

Citations:  Bibtex RefMan EndNote GB/T7714

 ORCID:

Dong-dong Gu

https://orcid.org/0000-0002-8258-6935

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Journal of Zhejiang University SCIENCE A 2018 Vol.19 No.2 P.111-121

http://doi.org/10.1631/jzus.A1700599


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


Author(s):  Jie Liu, Dong-dong Gu, Hong-yu Chen, Dong-hua Dai, Han Zhang

Affiliation(s):  College of Materials Science and Technology, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China; more

Corresponding email(s):   dongdonggu@nuaa.edu.cn

Key Words:  Selective laser melting (SLM), AlSi12, Surface morphology, Single track


Jie Liu, Dong-dong Gu, Hong-yu Chen, Dong-hua Dai, Han Zhang. Influence of substrate surface morphology on wetting behavior of tracks during selective laser melting of aluminum-based alloys[J]. Journal of Zhejiang University Science A, 2018, 19(2): 111-121.

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author="Jie Liu, Dong-dong Gu, Hong-yu Chen, Dong-hua Dai, Han Zhang",
journal="Journal of Zhejiang University Science A",
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publisher="Zhejiang University Press & Springer",
doi="10.1631/jzus.A1700599"
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%T Influence of substrate surface morphology on wetting behavior of tracks during selective laser melting of aluminum-based alloys
%A Jie Liu
%A Dong-dong Gu
%A Hong-yu Chen
%A Dong-hua Dai
%A Han Zhang
%J Journal of Zhejiang University SCIENCE A
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%@ 1673-565X
%D 2018
%I Zhejiang University Press & Springer
%DOI 10.1631/jzus.A1700599

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T1 - Influence of substrate surface morphology on wetting behavior of tracks during selective laser melting of aluminum-based alloys
A1 - Jie Liu
A1 - Dong-dong Gu
A1 - Hong-yu Chen
A1 - Dong-hua Dai
A1 - Han Zhang
J0 - Journal of Zhejiang University Science A
VL - 19
IS - 2
SP - 111
EP - 121
%@ 1673-565X
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PB - Zhejiang University Press & Springer
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DOI - 10.1631/jzus.A1700599


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.

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

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

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