Developing a High-Strength Al–Mg–Si Alloy with Improved Electrical Conductivity by a Novel ECAP Route

This paper investigated the microstructure, tensile and electrical properties of an equal channel angular pressed 6063 Al alloy at temperatures ranging from room temperature (RT) to 300 ℃. Additionally, a two-step temperature schedule (TST) was applied to improve the combined property of the low-alloyed Al–Mg–Si alloy. The results suggested that only processing at RT and TST led to a reduction of the grain size and an increase of strength with increasing number of passes, whereas four-pass processing at TST condition produced a better grain refinement and higher strength compared to the RT counterpart. Detailed analysis reveals that apart from the grain refinement, high-density dislocations and formation of nanoscale precipitates play the dominant roles in strengthening. These microstructural features provide the four-pass TST sample exceptional increase in strength about 67 MPa compared to RT counterpart. Besides, precipitation of solutes in form of numerous nanoscale precipitates can purify the Al matrix in the TST samples, resulting in the improved electrical conductivity as compared to RT sample. The TST method as a new strategy can improve strength and electrical conductivity by controlling the nanosized precipitates in an ultrafine-grained structure, which indeed provides an opportunity for low-alloyed Al–Mg–Si alloys to obtain the better combination properties. Graphical Abstract