The Effect Of Hpt On Solid Solution And Aging Of AZ31B And ZK60 Magnesium Alloy

As a typical metal material with the lightest commercial metal structural,magnesium and magnesium alloys with many excellent performance,areattracting more and more attention and has a very good applicationprospectprospect.However,magnesium alloy always exhibit poor workability and ductility at room temperature and low intensity and poor corrosion resistance which limits the activation of slip systems.The high-pressure torsion(HPT)has become one of the effective means to prepare ultrafine grained(UFG)materials in China and other countries.Heat treatment is one of the effective means to improve the mechanical properties of the magnesium alloys.Therefore,investigating the influence of high pressure torsion + heat treatment on the properties of magnesium alloy from micro perspectives has an important guiding significance for promoting the practical value of magnesium products.The materials used in present study were the most common-used commercial AZ31 B and ZK60 Mg alloys.A main research content of this paper is to study the effect of HPT+ aging treatment on microstructure and mechanical property in Mg alloys.Another main research content of this paper is to study the effect of HPT deformation on aging precipitation of Mg alloys.Firstly,In this paper,After the as-cast magnesium alloy was homogenized at 420? for 12 h a commercial AZ31 B and ZK60 magnesium alloys was processed by solution treatment,high-pressure torsion + solution treatment,solid solution + aging treatment,solid solution + high pressure torsion + aging treatment respectively.X-ray diffraction(XRD),scanning electron microscopy(SEM),the optical microscope(OM)and other research methods were used to study the changes in the microstructure and structure of the alloy.Using hardness test as alloy's comprehensive performance standards.The mechanisms are analyzed and the experimental results show that HPT can promote the dissolution of the second phase,reduce the solid solution temperature and shorten the holding time.In addition,HPT can significantly refine the alloy grain to ultra-fine grain,but high pressure torsion + solid solution treatment has no obvious effect on improving the hardness of AZ31 B and ZK60 magnesium alloys.HPT treatment alone cannot precipitate the second phase out of solid solution AZ31 B and ZK60 magnesium alloy,but HPT can promote the second phase out of AZ31 B and ZK60 magnesium alloy in the subsequent aging process to shorten the aging time and reduce the aging temperature,and the larger the deformation,the easier the second phase out.HPT treatment can refine the size of precipitate and change the morphology of precipitate.In this study,the maximum microhardness of AZ31 B alloy was 127 HV in the state of solid solution +HPT 5 turns.The hardness of solid solution ZK60 magnesium alloy HPT was about 94% higher than that of solid solution alloy 64 HV when it reached the maximum value of 124 HV after 5 turns of treatment.