Nanoscale multi-gradient ordered architectures driven exceptional strength and ductility in low thermal expansion magnesium alloy.

Abstract

Alloys with low thermal expansion, high strength, and superior plasticity are crucial for critical applications in industries such as aerospace. Although the in-situ formation of low or negative thermal expansion particles presents a promising strategy, these materials generally suffer from limited ductility. Here, we demonstrate that the construction of nanoscale gradient ordered architectures can effectively addresses this limitation. By facilitating the diffusion and reaction of aluminum (Al) atoms into boronized manganese (Mn-B), we induce a gradient ordering architecture between rare-earthed magnesium (Mg) alloys and MnB phase, achieving a near-zero thermal expansion coefficient of 0.8 × 10^-6·°C^-1 within the temperature range of 280-320 °C. As fully transitioning from Mn-B to a multi-gradient ordered Mn-Al-B configuration results in a stabilized thermal expansion coefficient of 23 ×10^-6·°C^-1 across a broad temperature range (25-400 °C). This nanoscale architecture not only mitigates brittle interfacial fractures by maintaining the mechanical integrity but also enables the Mg alloy to reach an ultrahigh compressive strength of 507 MPa, with a 23.8% compressive strain. Our findings highlight the potential of designing gradient ordered architectures as a strategic approach to enhance the mechanical properties of lightweight alloys.