P = μ * F * vFriction isn't just resistance; it’s a heat engine. When rotational speed drives the energy density beyond the material’s lattice stability, the solid phase yields and flows plastically. This process converts macro-scale motion into micro-scale thermal vibrations, softening the material without melting. Thermodynamics is indifferent to hardness scales such as Mohs; it responds to the rate of energy dissipation and entropy production. Friction stir welding is used for joining high-st