The evolution of microstructure and texture of AZ80 Mg alloy cup-shaped pieces processed by rotating backward extrusion

This study proposed an effective plastic deformation technique,rotating backward extrusion(RBE),for producing high performance AZ80 magnesium alloy cup-shaped pieces.The RBE process was carried on the Gleeble-3500 test machine at 653 K,and the conventional backward extrusion(CBE)was also conducted for comparison.A detailed microstructure analysis was performed using the optical microscopy(OM)and electron back-scatter diffraction(EBSD).The results shown that the equivalent strain and deformation uniformity of the cup pieces could be substantially increased by the RBE process compared with the CBE process.Furthermore,the RBE process could significantly improve the grain refining capacity and the proportion of dynamic recrystallization(DRX),of which the maximum reduction of grain size was 88.60%,and the maximum increase of DRX proportion was 55.30%in the cup bottom.The main deformation mechanism of the RBE process was the discontinuous DRX(DDRX),while the continuous DRX(CDRX)was also occurred in the cup transition.Compared with the CBE sample,the texture of the cup bottom was weakened for the RBE sample.The microhardness value of the RBE sample was higher than that of the CBE sample,which can be attributed to the grain refinement strengthening.

Rotating extrusion technique and its effect on quality of aluminum alloy thin-plate weldments

A new technique named rotating extrusion was proposed that uses rotating extrusion action to rectify residual distortion of aluminum alloy thin-plate weldments to improve mechanical properties of welded joints. The basic principle and device of rotating extrusion were introduced. The residual distortion and stresses in rotating extrusion weldments were compared with those in conventional weldments. The differences in microstructure and mechanical properties between conventional welded joints and rotating extrusion welded joints were investigated and analyzed in order to make clear the effect of rotating extrusion on the performance of aluminum alloy weldments. Experimental results show that rotating extrusion can enhance the hardness and tensile strength of aluminum alloy welded joints evidently. This method has also potential effect on extending the life of welded structures.

Reducing residual distortion of thin-plate weldments by rotating extrusion

A new method named rotating extrusion was developed to mitigate residual distortion of thin-plate weldments. The basic principle and characteristic of rotating extrusion as well as an efficient rotating extrusion device were introduced. Systematic trials were conducted to investigate the influence of several technological parameters including the distance between the extrusion tool and welding torch, the pressure acting on weldment, the dimension of the extrusion tool and its rotational speed on distortion control effect. Experimental results show that, as for 2A12T4 aluminum alloy weldment with 2 mm in thickness, 150 mm in width and 350 mm in length, when appropriate technological parameters are adopted, rotating extrusion can reduce its buckling deflection to below 3% of the original value. Implementing rotating extrusion during welding with an extrusion tool more than 100 mm away from the welding torch may achieve better distortion mitigation effect.

Effect of welding with trailing rotating extrusion on fatigue strength of aluminum alloy welded joints

Welding with trailing rotating extrusion is a new method designed to improve the welding quality of aluminum alloy thin-plate weldments. The effect of this technology on fatigue strength of aluminum alloy welded joints was investigated and analyzed in this paper. Experimental data show that welding with trailing rotating extrusion can improve the fatigue strength of aluminum alloy weldments remarkably,