What is my laptop's heatsink made out of? Copper? or Aluminum-copper alloy?

I have the latest
Spectre x360 - 15-df0068nr (Late 2018) - 8565U cpu, MX150 gpu

I'm looking into re-pasting the CPU/GPU with liquid metal. I can only do this if my heatsink is not made out of aluminum. The part that touches the CPU/GPU is definitely copper colored. But not all heatsinks are 100% copper. I think a lot of them have some aluminum in it. Is there a way to check? Does someone have any insight to what the general standard is these days? Is it okay to use liquid metal even if it has some aluminum in it (copper-aluminum alloy).

service manual (add ".pdf" to end of the file name): http://h10032.www1.hp.com/ctg/Manual/c06162318

- HP spare part number for heatsink: L38110-001 (pg.21 # (7))

- Picture of heatsinks: pg.60 bottom figure

- the first unit I had was completely copper colored, the 2nd unit had the top painted black, bottom was copper colored (including the part that makes contact with the CPU/GPU)

 

No such thing as a copper-aluminum alloy.
If the heatplate is copper, it means that the base (the part touching the CPU) is copper. The other parts around it may be aluminum or the radiator fins. Many heatsinks have a copper base and aluminum body.

If the aluminum is right next to the copper without any spacing or standoffs, you need to put some sort of foam dam or barrier around the copper so the LM doesn't drip off.

 

Thank you! I was just editing the post to ask "...maybe the plate is made out of copper and the fins are made out of aluminum?"

Thanks so much for the clarification. Any experience with liquid metal on laptops? Some say if I move it around a lot (which I do) it'll spill the LM over the other parts of the laptop. Others say that they had no problem whatsoever on multiple laptops after moving it around for years (give proper application = thin layer).