Keyhole threshold and morphology in laser melting revealed by ultrahigh-speed x-ray imaging
Keyhole threshold and morphology in laser melting revealed by ultrahigh-speed x-ray imaging
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DOI：
10.1126/science.aav4687
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发表时间：
2019-02-22
期刊：
影响因子：
56.9
通讯作者：
Rollett, Anthony D.
中科院分区：
文献类型：
--
作者：
Cunningham, Ross;Zhao, Cang;Rollett, Anthony D.
我们使用超高速同步加速器 X 射线成像来量化增材制造中金属激光熔化过程中的蒸气凹陷（也称为锁孔）现象。尽管是从焊接中预期的并从熔化区的死后横截面推断出来的，但用高能 X 射线对匙孔形态和动力学的直接可视化表明：(i) 在激光粉末床熔合所使用的功率和扫描速度范围内都存在匙孔； (ii) 基于激光功率密度，从传导模式到小孔有一个明确的阈值； (iii) 转变遵循汽化、液体表面凹陷、不稳定以及深匙孔形成的顺序。这些和其他方面为激光粉末床机中的三维打印提供了物理基础。
We used ultrahigh-speed synchrotron x-ray imaging to quantify the phenomenon of vapor depressions (also known as keyholes) during laser melting of metals as practiced in additive manufacturing. Although expected from welding and inferred from postmortem cross sections of fusion zones, the direct visualization of the keyhole morphology and dynamics with high-energy x-rays shows that (i) keyholes are present across the range of power and scanning velocity used in laser powder bed fusion; (ii) there is a well-defined threshold from conduction mode to keyhole based on laser power density; and (iii) the transition follows the sequence of vaporization, depression of the liquid surface, instability, and then deep keyhole formation. These and other aspects provide a physical basis for three-dimensional printing in laser powder bed machines.