7075（Al-Zn-Mg-Cu）ultrafine-grained aluminum alloy ribbon was prepared by single roller melt rotary cooling method

and hot extrusion was performed at 400～500 ℃to obtain ultrafine grain 7075 aluminum alloy bar.The microstructure

mechanical properties and tensile fracture of the extruded bar were tested and analyzed.Scanning electron microscopy（SEM）analysis indicates that the rapid solidification method can refine significantly the grains

and the average grain size of the prepared ribbon is less than 1μm.The back-scatter diffraction（EBSD）results demonstrate that the bar obtained by hot extrusion from the ultrafine grain ribbon presents a significantly finer grain and better mechanical performance than the conventional cast hot extruded bar.Under the test conditions

with the hot extrusion temperature increase

microstructure of the extruded bar is gradually densified.Although the grains are coarsened

the strength and plasticity are still improved.At 500℃

the hot extruded bar exhibits the desirable mechanical performance

where the tensile strength and elongation reach 517.1 MPa and 23.2%

increased by 12.0%and 51.6%

respectively

compared with those of the traditional casting hot extrusion bar.