Aluminum is not the most "critical export" for Russia.
The Russians are exporting oil,natural gas,grain,precious metals,weapons,etc.
I'm sure that the Russians won't mind reducing their aluminum export.The biggest problem for the Russians is actually the import.How would they replace the goods,services and technologies that were imported from the west?Buying goods and technologies from China and other Asian countries is a possible option.
Another big problem for Russia would be the EU refusing to buy Russian oil and gas,but this is highly unlikely to happen right now.