Scientists from the Institute of Metal Research, Chinese Academy of Sciences (IMR, CAS), have developed a defect promoted “internal decomposition” mechanism for Ti₂AlC MAX phase precursors, enabling the fabrication of a hierarchical Al₃Ti/Al composite that simultaneously achieves high strength and high modulus at elevated temperatures, overcoming the long standing drawback that has limited the high temperature application of aluminum matrix composites (AMCs).
AMCs are widely used in aerospace and other lightweight structural applications due to their high specific strength and specific modulus. However, interfacial degradation and matrix softening at elevated temperatures have historically limited their service temperature to below 300 °C. To improve high-temperature performance, in-situ AMCs with strong metallurgical interfaces have attracted considerable attention. But conventional reaction systems face a stubborn dilemma: micron-sized precursors offer low specific surface area, leading to insufficient reaction and coarse, agglomerated reinforcements that limit strength gains; nano-sized precursors, while capable of producing nanoscale reinforcements, are prone to agglomeration and yield low reinforcement volume fractions, making it difficult to achieve high modulus.
The research team overcame this challenge by introducing a defect‑promoted internal decomposition mechanism. Using high‑energy ball milling to induce a dual‑pathway elemental diffusion architecture in Ti2AlC, the team enabled the internal decomposition of the MAX phase, producing a hierarchical microstructure containing two key features: high volume fraction sub-micron Al3Ti particles uniformly dispersed in the ultrafine‑grained Al matrix, and intraparticle carbon-contained clusters and rod-like phases dispersed within the Al3Ti particles. The hierarchical Al3Ti/Al composite featured a multi-level strengthening mechanism, enhancing the high-temperature performance of the composite.
This hierarchical design delivers outstanding mechanical performance at high temperatures. At 350 °C, the composite exhibits an ultimate tensile strength of 246 MPa and a Young’s modulus of 106 GPa. Its specific modulus at 350 °C surpasses that of Ti alloy TC4, Cu alloy QZr0.2, 45 steel, and Ni‑based alloy GH93 by margins of 88%, 190%, 55%, and 42%, respectively.
The work, published in Nature Communications, opens a new pathway for designing lightweight structural materials for demanding high‑temperature aerospace and defense applications.
Fabrication process and microstructure of the composite. (Image by IMR)
Elemental diffusion pathways in the defective Ti2AlC particles. (Image by IMR)
Microstructure of the composite Al3Ti particles. (Image by IMR)
High-temperature mechanical properties of the composites. (Image by IMR)
Microstructure of the composites after tensile deformation. (Image by IMR)
