Research On Microstructure And Propetries Of ZK31Magnesium Alloy Aging Process

Magnesium alloys have such advantages as low density, high specific strength, largereserves, etc. It has been applied in the automotive, aerospace and some other aspects.Wrought Magnesium Alloys has a more broad application prospects which because of itsbetter performance. The mechanical properties of wrought magnesium alloys can befurther improve by alloying of rare earth elements and appropriate heat treatment. It is animportant research direction of wrought magnesium alloysIn order to understand the impact of rare earth elements on the aging process and themechanical properties of aging in wrought magnesium alloys. The topics selected ZK31magnesium alloy with different levels of rare earth Y with extrusion and aging treatment.Analyzed microstructure and mechanical properties of cast, extruded, aging alloys. Focuson the effect of Y on the mechanical properties of aging process from the ZK31-Ymagnesium alloy microstructure evolution point of view. Aims to provide the basis forimprove the mechanical properties by rare earth.Observe and Analysis the microstructure of cast state, homogenized state, extrudedstate, solid solution state, aging state alloys by using optical and electron microscopy,X-ray diffraction analysis methods. The results show that rare Y can reduce the grain sizeof cast alloys. Amount of0.5%is the best. But Y will be promoting the eutectic reactionand form Mg3Y2Zn3intermetallic compound phase. Compared with cast alloys grains sizeincrease and compound of the grain boundary phase reduced after homogenization. Alloydynamic recrystallization phenomenon occurs in hot extrusion process. Rare Y caneffectively limit the size of recrystallized grains. In the solution process, the recrystallizedgrains will grow while the original Mg-Zn binary metal compound on the grain boundarieswill decomposes. But the Mg-Zn-Y ternary phase has a better thermal stability. Precipitatesin the grain interior will appear in solution process. Rare Y inhibit grain growth in theaging process. Precipitates appear in grains after T5treatment. The precipitates appeared insolution process grows after T6treatment.Using vickers hardness tester, universal testing machines to test the mechanicalproperties of the alloy. The result shows that for all experimental alloys, the tensile strength and elongation at break of extruded state and aged state is better than cast state. Effect ofRare Earth Y on the T5magnesium alloy state tensile strength is increased and thendecreased. Alloy with0.5%Y has the best tensile strength. But tensile strength decreasewith rare overdose. Down from383.9Mpa with amount of0.5%Y to318.7Mpa. Rare canincrease the elongation at break of T5state magnesium alloy, from14.8without rare to17.2%with amount of2.0%Y. A large number of precipitates appear after T5treatment.These precipitates played a good role in strengthening the drawing process. Tensilestrength of T6state alloy is lower than T5state. It reach the maximum295.4Mpa withamount of0.5%Y. Decreased by about23%. However, T6state alloy has the best plastic.The elongation at break increasing with the increasing of amount of Y. Increased from19%without rare to28.1%with2.0%rare.