Lightweight metals, e.g. aluminum (Al), magnesium (Mg), titanium (Ti) and their alloys are of great importance for applications in various machinery and transportation system, espe‐ cially in aerospace and automobile products due to their high strength-to-weight ratio and superior physical and chemical performances. However, their poor tribological properties, such as low wear resistance, high friction coefficient and difficulty to lubricate, have seriously restricted their extensive applications.