Except for bamboo and wood, I think I've used bikes made from every material and a properly built mtb frame doesn't have aluminum buzz.

The material of the bars is more important than the material of the frame. For instance, you will find carbon or ti or light aluminum bars to be better than steel bars for reducing buzz. Additionally, the sweep back angle of the bars can be critical to reducing hand/wrist pain. I only use bars with a 9-11 degree sweep due to wrist pain.

Tire and fork pressure make a big impact.

Don't get stuck on the material. Focus on design and functionality, and proper pressure.