Process-dependent anisotropic thermal conductivity of laser powder bed fusion AlSi10Mg: impact of microstructure and aluminum-silicon interfaces
Process-dependent anisotropic thermal conductivity of laser powder bed fusion AlSi10Mg: impact of microstructure and aluminum-silicon interfaces
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DOI：
10.1108/rpj-09-2022-0290
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发表时间：
2023-02-03
影响因子：
3.9
通讯作者：
Schiffres, Scott N.
中科院分区：
文献类型：
--
作者：
Azizi, Arad;Hejripour, Fatemeh;Schiffres, Scott N.
目的si10mg合金具有可印刷性好、导热系数相对较高、密度低、力学性能好等优点，被广泛应用于激光粉末床熔合。然而，作为建筑材料的导热系数作为加工（能量密度、激光功率、激光扫描速度、支撑结构）和建筑方向的函数，在文献中没有得到很好的探讨。本研究旨在阐明工艺、微观结构与导热系数之间的关系。采用闪散率和频域热反射（FDTR）技术研究了激光粉末床熔合（L-PBF） AlSi10Mg样品的热导率。热导率与L-PBF AlSi10Mg的微观结构有关，并随加工条件的变化而变化。在所有能量密度下，通面热导率均大于面内热导率。利用频域热反射图（FDTR）和电子背散射衍射图（EBSD）的共定位热导图来研究微观结构对热导率的影响。在59 J/mm(3)时获得了最高的通平面热导率（136 +/- 2 W/m-K），超过了先前报道的值。面内导热系数在50 J/mm时达到峰值117 +/- 2 W/m-K(3)。在相同孔隙率下，导热系数随能量密度降低的趋势主要是由于减小的晶粒尺寸产生了更多的Al-Si界面，从而形成热阻。在这些界面处，热能必须从铝中的电子转化为硅中的声子。同位的热导率和晶体学晶粒取向图证实，较大的柱状晶粒比较小的柱状晶粒具有更高的热导率。AlSi10Mg的热性能对传热应用至关重要，包括增材制造的散热器，冷板，蒸汽室，热管，外壳和热交换器。此外，基于热的无损检测方法在缺陷检测和L-PBF工艺模拟等应用中需要这些特性。L-PBF工艺和组件的工业标准可以将这些数据用于热应用。原创性/价值据作者所知，本文首次制作了与L-PBF AlSi10Mg铝合金微观结构相匹配的耦合导热系数图。这是通过独特的内部热导率测绘装置实现的，并将数据与本地SEM EBSD图相关联。这提供了第一个确凿的证据，证明更大的晶粒尺寸可以为这种加工方法和材料系统实现更高的导热性。该研究还表明，控制凝固可以导致更高的导热系数。这也是第一个发现构建基板（有或没有支撑）对导热性有很大影响的研究。
PurposeAlSi10Mg alloy is commonly used in laser powder bed fusion due to its printability, relatively high thermal conductivity, low density and good mechanical properties. However, the thermal conductivity of as-built materials as a function of processing (energy density, laser power, laser scanning speed, support structure) and build orientation, are not well explored in the literature. This study aims to elucidate the relationship between processing, microstructure, and thermal conductivity. Design/methodology/approachThe thermal conductivity of laser powder bed fusion (L-PBF) AlSi10Mg samples are investigated by the flash diffusivity and frequency domain thermoreflectance (FDTR) techniques. Thermal conductivities are linked to the microstructure of L-PBF AlSi10Mg, which changes with processing conditions. The through-plane exceeded the in-plane thermal conductivity for all energy densities. A co-located thermal conductivity map by frequency domain thermoreflectance (FDTR) and crystallographic grain orientation map by electron backscattered diffraction (EBSD) was used to investigate the effect of microstructure on thermal conductivity. FindingsThe highest through-plane thermal conductivity (136 +/- 2 W/m-K) was achieved at 59 J/mm(3) and exceeded the values reported previously. The in-plane thermal conductivity peaked at 117 +/- 2 W/m-K at 50 J/mm(3). The trend of thermal conductivity reducing with energy density at similar porosity was primarily due to the reduced grain size producing more Al-Si interfaces that pose thermal resistance. At these interfaces, thermal energy must convert from electrons in the aluminum to phonons in the silicon. The co-located thermal conductivity and crystallographic grain orientation maps confirmed that larger colonies of columnar grains have higher thermal conductivity compared to smaller columnar grains. Practical implicationsThe thermal properties of AlSi10Mg are crucial to heat transfer applications including additively manufactured heatsinks, cold plates, vapor chambers, heat pipes, enclosures and heat exchangers. Additionally, thermal-based nondestructive testing methods require these properties for applications such as defect detection and simulation of L-PBF processes. Industrial standards for L-PBF processes and components can use the data for thermal applications. Originality/valueTo the best of the authors' knowledge, this paper is the first to make coupled thermal conductivity maps that were matched to microstructure for L-PBF AlSi10Mg aluminum alloy. This was achieved by a unique in-house thermal conductivity mapping setup and relating the data to local SEM EBSD maps. This provides the first conclusive proof that larger grain sizes can achieve higher thermal conductivity for this processing method and material system. This study also shows that control of the solidification can result in higher thermal conductivity. It was also the first to find that the build substrate (with or without support) has a large effect on thermal conductivity.