Coupling Effect of Mn Addition and Deformation on Mechanical and Electrical Properties of Al-Zr Alloys

In order to increase the strength of Al-Zr alloys, which are promisingly used for heat-resistant conductors, the coupling effect of Mn addition (0.16 wt.% and 0.88 wt.%) and deformation on the precipitation, mechanical, and electrical properties of an Al-0.18wt.% Zr alloy was studied using transmission electron microscopy (TEM), atom probe tomography (APT), hardness testing, and electrical conductivity measurement, respectively. Results showed that the Mn addition fully suppresses the Al3Zr precipitation in both hot-deformed and undeformed cases, which is mainly due to a strong Mn-vacancy bonding, in which Mn atoms seize vacancies and hence reduce the available vacancies for Al3Zr nucleation. Minor 0.16 wt.% Mn addition causes a simultaneous decrease in hardness and electrical conductivity, regardless of whether there is deformation. The higher 0.88 wt.% Mn addition, however, significantly increases the hardness by over 40%, especially in combination with deformation. Possible influencing factors such as grain size, dislocations, intergranular/intragranular precipitation, and solute clusters are comparatively discussed in terms of microstructural features and mechanical/electrical properties that are tuned by Mn addition and/or deformation. It is found that the Mn addition can make remarkable contributions to the hardness and thermal stability of the Al-Zr alloys when coupled with deformation.