| Magnesium alloys, as light structural materials, exist many advantages, such as low density, high specific strength, high specific stiffness, electromagnetic shielding performance and easily recycled etc. So, magnesium alloys are known as 'the green project materials having development potential and best future in the 21st century'. But, magnesium has hcp crystal structure, slip system is little and then plastic deformation is hard. The poor production efficiency has become the main obstacle to the extensive use of wrought magnesium alloys.Our previous research indicated that the additions of 1%RE and l%Sb to AZ31 as-cast alloy could improve the microstructure and property. By means of optical microscopy (OM), x-ray diffractometry (XRD), scanning electron microscopy (SEM) equipped with an Energy Dispersive Spectrometer (EDS) system, thermal simulation, tensile and impact toughness testing, the effects of RE and Sb on microstructure and properties of AZ31 wrought alloys at hot-extruding states were investigated. The influence of RE and Sb on plastic deformability and its mechanisms were also discussed.The effects of antimony and rare earth on the flow stress and dynamic recrystallization of AZ31 magnesium alloy was investigated by hot compression testing on the Gleeble-1500D thermal simulator. The results indicated that the additions of 1%RE and 1%Sb to the AZ31 magnesium could effectively improve the deformation resistance and accelerate the dynamical recrystalization.The results of hot-extruding showed that: with the heighten of temperature, the degree of dynamical recrystalization increased, but the grains grew up; dynamical recrystalization increasd and grains were refined when the extrusion ratio enhanced. At certain hot-extruding parameter (T=380℃,λ= 17.4), the mixed structure of original grains and recrystallized grains were found in AZ31 alloy; the additions of 1%RE and 1%Sb to the AZ31 magnesium could accelerate the dynamical recrystalization effectively and the microstructure was refined, the rare earth phase assumed chain distribution.With the addition of 1%RE to AZ31 alloy, the tensile strength improved about 5.5%, specific elongation and impact toughness increased 2.2%, and 5%, respectively, compared with that of AZ31 at hot-extruding state. Addition of 1%RE and 1%Sb could achieve better mechanical properties. Tensile strength, specific elongation and impact toughness of it improved 7.7%, 11.1% and 17.5%, respectively. The analysis of the tensile fracture morphology of the hot-extruding alloys showed that with the addition of 1%RE and 1%Sb, dimples were regnant, tearing rib was seen apparently, cleavage and quasi-cleavage were nearly observed. The alloys showed mainly tenacity fracture.The thick acicular-shape Al-RE phases dispersed on grain boundary of AZ31-1%RE alloy as-cast. By the extrusion, the acicular-shape rare earth phase broken up to polygon particle and presented chain distribution. But the shape and distribution of the Al-RE phase rended basal body of the alloy and induced stress concentration, so the toughness and elongation were reduced. By the addtion of Sb to the AZ31-1%RE, the acicular-shape Al-RE phases changed to the globular-shape RE-Sb phases and mainly distributed inside the grains as-cast. By the extrusion the globular-shape phase broke up and distributed more homogeneously and the toughness and elongation were increased. So the deformability was improved.The highest extrusion velocity of AZ31 was 2.3 m/min at 380°C. When the extrusion temperature increased to 420°C, the grain size grew coarser and the surface of the bars appeared burning loss. But the highest extrusion velocity of AZ31-1%RE-1%Sb could achieve 3.8 m/min at 420°C without horizontal crack or burning loss. The great increase of the extrusion velocity could effectively improve the production efficiency of the extrusion.
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