Abstract
In this paper we have used laser powder bed fusion (PBF) to manufacture and characterize metal microwave components. Here we focus on a 2.5 GHz microwave cavity resonator, manufactured by PBF from the alloy AlSi10Mg. Of particular interest is its thermal expansion coefficient, especially since many microwave applications for PBF produced components will be in satellite systems where extreme ranges of temperature are experienced. We exploit the inherent resonant frequency dependence on cavity geometry, using a number of TM cavity modes, to determine the thermal expansion coefficient over the temperature range 6–450 K. Our results compare well with literature values and show that the material under test exhibits lower thermal expansion when compared with a bulk aluminium alloy alternative (6063).
Highlights
Additive manufacturing (AM) is a modern fabrication process that enables three-dimensional components to be built using multiple twodimensional layers
Components produced by laser powder bed fusion (PBF, one form of AM) are being utilised in satellite feed chains due to the ability to achieve up to 99.8% density but with a 50% weight reduction compared to the subtractive manufactured equivalents [1], AM adoption in this field is still in its infancy [2]
This study uses a fractional frequency shift method to evaluate the true coefficient of thermal expansion (CTE) of an aluminium cylindrical microwave cavity produced through PBF over a wide temperature range (6–450 K) without the need for strict calibration. This is the first time that CTE has been assessed over a wide range of temperature, as is appropriate for spacebased components, using a passive microwave structure that can be adopted in a satellite communications system
Summary
Additive manufacturing (AM) is a modern fabrication process that enables three-dimensional components to be built using multiple twodimensional layers. For aluminium (of bulk conductivity 2.63 × 107 S/m) the skin depth at 2.5 GHz is calculated to be ≈2 μm, and so even micro surface features can have a significant impact on current flow and microwave loss. To overcome these losses, post processing techniques such as machine polishing [10] and silver plating are often employed [9,11,12]. This is the first time that CTE has been assessed over a wide range of temperature, as is appropriate for spacebased components, using a passive microwave structure (produced by PBF) that can be adopted in a satellite communications system
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