Submillimeter-thick stable gradient nanograined surface layer greatly reduces dry-sliding coefficient of friction in Cu alloys.

Severe plastic deformation (SPD) with deformation strain significantly larger than one is effective to strengthen metals and alloys. However, such a method will not work for Mg alloys due to their low deformability. In view of this problem, we propose a new alloy strengthening scheme of low-strain deformation, which is to introduce massive twins and stacking faults in coarse grain interior by rotary swaging (RS) at room temperature. By using this scheme, we successfully prepared an ultra-light bulk Mg-Li alloy with new strength record. GRAPHICAL ABSTRACT IMPACT STATEMENT This paper explored a new strengthening way of low deformation strain for metals and alloys and successfully prepared a strongest ultra-light Mg–Li alloy by low-strain rotary swaging process.