Lanzhou University of Technology Research Team Achieves Major Breakthrough in Rare Earth Composite Master Alloys

A research team from the School of Metallurgy and Environmental Engineering has made significant progress in the performance control of hypoeutectic aluminum-silicon alloys. The team has developed a novel Al-Ti-La-Sr composite master alloy that substantially enhances both the microstructure and mechanical properties of aluminum alloys with only trace addition. The research findings have been published in the Journal of Rare Earths, a leading international journal in the field of rare earth materials and non-ferrous metallurgy. Classified as a CAS Zone 1 TOP journal with an impact factor of 7.2 for 2024, the journal holds widespread academic influence and industry leadership in the international materials science community. The first author of the paper is Researcher Ding Wanwu from the School of Metallurgy and Environmental Engineering, with Researcher Ding Wanwu and Lecturer An Jiazhi serving as co-corresponding authors.

Industry Challenge

Hypoeutectic aluminum-silicon alloys, such as Al-7Si-0.3Mg, are key foundational materials for lightweight structural components in high-end equipment, including automotive engines and aerospace applications. However, their as-cast microstructure typically suffers from coarse α-Al grains and acicular (needle-like) eutectic silicon distribution. These issues lead to low tensile strength and poor ductility, making it difficult to meet the stringent requirements of high-end manufacturing for high-performance aluminum alloys. Conventional modification techniques often employ a combined treatment of grain refinement and silicon phase modification. Yet, Ti and Sr elements tend to exhibit antagonistic effects, resulting not only in limited performance improvement but also in higher addition levels and increased costs.

Innovative Solution & Mechanism

To address this common challenge in the industry, the research team innovatively developed an Al-Ti-La-Sr rare earth composite master alloy, successfully overcoming the technical bottleneck caused by mutual interference among traditional elements. The study found that the Ti₂Al₂₀La rare earth phase formed in the alloy plays a dual role. On one hand, it acts as an efficient heterogeneous nucleation site, significantly refining α-Al grains. On the other hand, through the release of Ti and La and the synergistic effect with Sr, it facilitates the transformation of eutectic silicon from acicular to granular morphology, while promoting the uniform precipitation of nano-scale secondary phases. This establishes a multi-scale synergistic strengthening mechanism combining grain refinement, silicon phase spheroidization, and nano-phase strengthening. Experimental results demonstrate that with only trace addition (≤0.2%) of the new composite master alloy, the tensile strength of the Al-7Si-0.3Mg alloy is increased by over 32%, yield strength by over 44%, elongation by over 95%, and microhardness by over 26%. The overall performance is significantly superior to the traditional Al-Ti-B + Sr process, effectively resolving the key industry pain points of elemental antagonism, high addition levels, and limited performance enhancement.

Future Outlook

Looking ahead, the research team will focus on the low-cost and efficient preparation of micro-nano rare earth phase master alloys, wire production, and engineering applications. The team aims to accelerate the translation and promotion of these research outcomes, supporting the technological upgrading of lightweight materials in new energy vehicles, high-end equipment manufacturing, and other fields, thereby contributing to the high-quality development of China’s non-ferrous metal materials industry.