Reciprocating extrusion device for universal testing machine and ultra-fine grain bar preparation method

The invention provides a reciprocating extrusion device for a universal testing machine and a preparation method of an ultra-fine grain bar. The reciprocating extrusion device comprises an upper die base plate, an upper female die, an inner sleeve, a sectioning extrusion die, an outer sleeve, a lower female die, a male die, a limiting ring and a male die fixing plate. Compared with a traditional reciprocating extrusion device, the reciprocating extrusion device can be used on a small-load universal testing machine, and the application way of the reciprocating extrusion technology is widened. The deformation temperature, the strain rate and the strain in the reciprocating extrusion process can be accurately controlled by utilizing a small-load universal testing machine, and the structure evolution of the material is more effectively regulated and controlled, so that the ultra-fine grain material with high toughness is obtained. According to the method, backward extrusion forming is adopted, forming loads can b