Question about assembling my own DIY AC Cable

I sent an email to Furutech now and asked them if their copper is alloyed

If you use copper as a base metal in a connector I can guarantee you it's not pure, and that's just fine.

Don’t overthink it. No need to know the molecular breakdown here. Use good connectors and you’ll be fine. 
I suggest contact enhancer mainly to prevent oxidation on bare wires over time from the remnants of oils left from your fingers. Deoxit will do as well. 

I agree with @audphile1 @erik_squires ​​​​@jea48 - don’t overthink it.

You are almost surely plugging the plug into a wall receptacle or power conditioner with brass, phosphor bronze, or beryllium copper contacts, and depending on what was used in your amplifier, you are probably plugging the IEC into an inlet with one of those same materials, unless either the designer used a higher level Furutech IEC inlet or you upgraded it. Furutech apparently uses copper connectors in their upper level products, as shown here.

Furutech replied already:

The listed products (FI-46, FI-48, FI-50) have pure OFC grade copper with no nickel plating and direct gold or rhodium plating. It is not a copper alloy.
I hope this information helps.

Kind regards,
Graeme
Furutech Co., Ltd.
Tokyo