Hot Tensile Deformation Characteristics And Hot Processing Map Of Extruded AZ80 Magnesium Alloys

With the development of world industry, the production of magnesium alloy is increased rapidly. Because of magnesium alloy possess more multipurpose properties than other materials, the demand of the magnesium alloy is increasing. In order to explore the best process parameters during the deformation of hot tensile experiment,in this subject, see the extrusion AZ80 magnesium alloy as the research object, and establish the hot processing map under constant temperatures of 250~450°C and strain rate of 10-2~5×10-4 s-1. Thus, supplying the basis for the development and application of plastic technology of extrusion AZ80 magnesium alloy.The elongation-to-failure tests of extrusion AZ80 magnesium alloy was conduted at temperatures from 250℃ to 450℃ and strain rates from 10-2 s-1 to 5×10-4 s-1 to analysis the influence of forming temperature, strain rate, and strain to the multipurpose during thermal tensile. The results show that, at the same strain rate, the yield stress decreases with the increase of temperature, and the deformation zone of steady state becomes larger. At the same forming temperature, the strain and the peak of stress decrease with the decrease of strain rate, when the deformation zones comes into steady state. The results of SEM shows that: in the same strain rate, the number of dimple decreases with the increase of forming temperature, and the dimple becomes bigger and deeper. The forms of fracture transforms to ductile fracture.The hot processing map was established with the temperature from 250℃ to450℃ and strain rates from 10-2 s-1 to 5×10-4 s-1, based on the EF experimental data.The results shows that there are stable zones and three unstable zones in the hot processing map of AZ80 magnesium alloy. According to our analysis and discussion shows that in stability zones there are two domains with high efficiency of power dissipation, the peak efficiency of domain 1 is 40.56% at 400℃ and a strain rate of10-2 s-1 and the peak efficiency of domain 2 is 19.78% at 250℃ and a strain rate of10-3 s-1. Domain 3 the temperature from 250℃ to 260℃ and the strain rate from 10-2s-1 to 5×10-3 s-1、 Domain 4 the temperature from 330℃ to 360℃ and the strain rate from 10-2s-1to 5×10-3s-1and Domain 5 the temperature from 380℃ to 450℃ and the strain rate from 10-3s-1to 5×10-3s-1are all in the instability and the zones where??)( ? is negative in these zones.These predictions are further validated by microstructural observations on the deformed specimens that the optimum processing parameters of hot tension for extruded AZ80 magnesium alloy with the temperatures from 400~450℃ and strain rates from 10-2~5×10-3 s-1, under this conditions can obtain the excellent microstructural. The optimum processing parameters are at temperatures from 400℃to 450℃ and strain rates from 10-2s-1to 5×10-3s-1based on the microstructural observations, which show much better microstructures under these conditions.