The thermal conductivity of aluminium at cryogenic temperatures varies by many orders of magnitude. Values for different alloys vary by about a factor of ten, while those for pure aluminium of different purities vary by more than three orders of magnitude. It is therefore not possible to give a single set of recommended conductivity values for aluminium.

However, a set of equations have been created which can extrapolate the thermal
conductivity of aluminium from a measurement at a single temperature
to the entire temperature range from the superconducting transition
(about 1 K) to 300 K. Equivalently, an electrical resistitivity or RRR
value may be used.
These equations apply to both pure aluminium[1]
and aluminium alloys[2].

The figure below shows conductivity values for various aluminium alloys,
produced by using these equations to extrapolate the results of
measurements in the literature taken over restricted temperature ranges.
For clarity, some types with similar values have been
grouped together.
For various reasons, including sample to sample
variations, these values should be taken as an indication only.
More information is given
here,
with a
more detailed explanation in reference [2], from which the figure
below was taken.

These links provide tabulated conductivity values for the alloys
shown above:
2014 (T651)
2024 (O)
2024 (T4)
2024 (T6)
2024 (T86)
2219 (T81)
3003 (F)
5052 (O)
5083 (O)
5086 (F)
5154 (O)
6061 (T6)
6063 (T5)
6082 (T6)
7039 (T61)
7075 (T6)
7075 (T73)
The
advanced aluminium thermal conductivity
calculator can be used to produce values for other alloys, if you
know the electrical or thermal conductivity at 4 K.

For pure aluminium, the best that can be done is to offer a range of
likely values for a given nominal purity. These are shown below for
*annealed*
aluminium with 4N (99.99%) to 6N (99.9999%) purity. The dashed lines
show values for 5N purity copper, with and without oxygen annealing,
for comparison. The graph is taken from reference [3],
which gives more detail.

These links provide tabulated conductivity values for the ranges
shown above:
4N - lower limit
4N - upper limit
5N - lower limit
5N - upper limit
6N - lower limit
6N - upper limit.
Values for arbitrary RRR (or 4 K conductivity values) can be produced
using the advanced aluminium thermal conductivity
calculator.

This page is currently in an experimental state. Although the results have been
checked, if you are using them for anything important, please check them
yourselves (perhaps using the references below).

I would appreciate reports of any problems (contact details given
here.)

[1] J. G. Hust and A. B. Lankford, "Thermal conductivity of aluminium,
copper, iron and tungsten from 1 K to the melting point",
National Bureau of Standards, Boulder, Colorado, 1984. NBSIR 84-3007.

[2] A. Woodcraft,
"Predicting the thermal conductivity of
aluminium alloys in the cryogenic to room temperature range",
Cryogenics 45(6): 421-432, 2005.

[3]
A. Woodcraft
"Recommended values for the thermal conductivity of aluminium of
different purities
in the cryogenic to room temperature range, and a comparison with copper"
Cryogenics 45(9):626-636, 2005.