Significant hardness improvement of a low-density Al-Si-Mg-Li-Fe alloy through laser-aging surface treatment

High hardness and low density are desirable merits of materials for wearproof structural applications. This paper develops an Al-10Si-2Mg-0.5Li-0.2Fe alloy that is 3.3% lighter than pure Al, and employs laser-aging surface treatment to improve its hardness. After the treatment, second phase particles from tens of micrometers are transformed to an average size smaller than 15 nm. Hardness of the alloy reaches 194 HV, entering the highest level of Al alloys lighter than pure Al. Meanwhile, corrosion resistance of the alloy in 3.5% NaCl aqueous solution is enhanced by about 34%, due to alleviated micro-galvanic corrosion. Equations are established for evaluating contributions from grain refinement hardening, solid solution hardening and precipitation hardening effects. Accordingly, they are calculated to account for 4.4%, 50% and 45.6%, respectively. This inspires high hardness Al alloy design through taking full advantage of oversaturation and nano-scale precipitation.

Automated summary

This paper develops a new type of aluminum alloy and improves its hardness through laser-aging surface treatment. The alloy exhibits high hardness and improved corrosion resistance. The study also establishes equations to evaluate the contributions of different hardening effects.