Ductile-to-brittle transition in aluminum alloys

Zhou, D.*; Zhang, X.*; Pang, X.*; Zhao, Z.*; Chen, X.*; Wei, S.*; Yang, C.*; Gong, W.   ; Harjo, S.   ; Li, R.*; Zhang, D.*; Qin, G.*

Here, we investigated the room-temperature (298 K) and cryogenic-temperature (77 K) mechanical behaviors of binary Al-Mg alloys over a wide range of Mg concentrations (2.8-13.1 at.%). A ductile-to-brittle transition was observed at 77 K as the Mg content increased from 7.5 to 13.1 at.%, accompanied by a significant decrease in impact energy from 161 J to 14 J. Through detailed theoretical calculations and experimental observations, this composition-dependent transition was found to be primarily associated with Mg segregation-induced grain boundary (GB) expansion and charge density depletion at the GB. These findings not only address the growing demand for durable lightweight materials for low-temperature applications, but also provide insights into the design of ultralight aerospace structural materials capable of withstanding the harsh environments encountered in space exploration.