Study On Microstructures And Properties Of Wrought Magnesium Alloys After Thermo-mechanical Processing

Magnesium and Magnesium its alloy are the lightest structure metallic material with low density, high specific strength, specific rigidity, and damping property, which have rich applications in aviation, aerospace, automotive, computer, electronics, communications and other fields. Due to limited mechanical properties, the applications of magnesium alloy are still far behind those of the steel and aluminum alloy, so the study on strengthening and toughening of magnesium alloy is one of the current research focus.In this dissertation, as the typical heat treatment of magnesium alloys AZ80 and ZK60 magnesium alloys are chosen to be as the research objects, on the basis of fine grain strengthening and toughing, texture strengthening and heat treatment strengthening theories, through the way of thermo-mechanical processing, to seek the coupling of multiple strengthening and toughening mechanisms pathways and determine the optimal process, in order to enhance magnesium alloy room temperature mechanical property and enlarge the range of use.The results of AZ80 magnesium alloy show that, the aging process can generate a large number of precipitated phase, a discontinuous precipitate phase showed a good strengthening effect; at 150 centigrade ageing 30h can reach peak ageing, the yield strength of 205.4 MPa, tensile strength of 292.5MPa, the ratio of the initial extruded materials are improved by 17% and 3.2%, but the elongation decreased, by squeezing the state fell to 1 11%. Of extruded materials used in ECAP process, although the strength decreases slightly, but significantly improves the toughness of plastic, at 220 centigrade ECAP four times after the material elongation reached 20.9%, the ratio of the initial extruded materials increased by 44.1%.The results of ZK60 magnesium alloy show that, in the aging state material have been found four types of second-phase precipitates; ageing 40h material strength reached the maximum, the yield strength of 281.9 MPa, tensile strength of 315.4MPa, the ratio of the initial squeezed state material, were increased by 24.9% and 12%. About ECAP after material analysis results show that, at 220 centigrade ECAP four times material, grain refinement effect is very significant, grain size of 500～800nm; in fine grain strengthening and toughening effect for 243.4MPa, yield strength, tensile strength of 292.2MPa, ratio of extruded material are increased by 7.8% and 6.9%, the rear extension rate to achieve 26.8%, than the extruded material is increased by 59.8%, with the best comprehensive mechanical properties. In general, on two kinds of as-extruded magnesium alloy materials for artificial aging can significantly enhance the strength of the material, to achieve a better grain refinement strengthening, texture strengthening and heat treatment strengthening coupling. While the ECAP state material for artificial aging treatment, two kinds of magnesium alloy on the mechanical properties of the material had no significant change, this is mainly due to ECAP state materials after aging precipitation strengthening effect and grain growth led to the softening effect of offset.