| Mg-RE alloys have good room temperature and high temperature tensile properties,fatigue properties and creep resistance.They are widely used in cutting-edge fields such as industrial production,aerospace and defense,but compared with deformed aluminum alloys.The strength is limited,and its popularization and application on the main bearing structure is limited.In this paper,the microstructure of the Mg-RE alloy is improved by applying an external field to improve the mechanical properties.In this paper,Mg-9Gd-3Y-1.2Zr-0.5Zn(GW93)alloy is used as research object,by using metallographic microscope,scanning electron microscope,energy spectrum analyzer,X-ray diffractometer,Brinell hardness tester and electronic universal testing machine.Analytical and testing methods were used to study the effects of ultrasonic treatment(power 0-2000W,time 0-120s)on microstructure,mechanical properties,solidification behavior and age hardening behavior of GW93 alloy,and to analyze the mechanism of improving alloy structure and improving mechanical properties.The main findings are as follows:(1)GW93 alloy is ultrasonically treated by different ultrasonic power and different time.The a-Mg phase of the alloy changes from dendrites to equiaxed crystals,and the shape of the second phase changes from agglomerated bulk to fine and dispersed.Granular,the grain size was reduced from 65 ?m to 13.5 ?m.After ultrasonic treatment of GW93 alloy melt,the comprehensive mechanical properties were significantly improved,and the tensile strength was improved by 73.3%compared with the unsonicated GW93 alloy.With the increase of ultrasonic power and ultrasonic time,the Brinell hardness,tensile strength and elongation of the as-cast alloy first increase and then decrease.When the ultrasonic power is 1000W and the ultrasonic time is 60s,the hardness,tensile strength and elongation The optimum values were 74.58HB,260 MPa,and 14.79%,respectively.After heat treatment,the mechanical properties of the alloy were further improved.The change rule was similar to that of the as-cast alloy.When the ultrasonic power was 1000W and the ultrasonic time was 60s,the hardness,tensile strength and elongation of the alloy were 106.92HB,346.67MPa and 19.65%,respectively.Compared with the as-cast alloy under the same conditions,the ultrasonic alloys were increased by 43.36%,33.33%and 32.86%,respectively.(2)The application of the ultrasonic field enhances the age hardening effect of the GW93 alloy,but does not change the overall law of age hardening.As the aging time increases,the Brinell hardness of the alloy first increases and then decreases gently.When the aging time is less than 10h,the Brinell hardness of the alloy increases slowly.When the aging time is 10h-43h,the Brinell hardness growth rate of the alloy increases greatly.As the aging time continues to increase,the Brinell hardness changes slowly.When the ultrasonic power is 1000W,the Brinell hardness reaches a maximum value of 106.92HB when the aging time is 43h,and the Brinell hardness is increased by 35.86%compared with the unsonicated alloy.(3)By analyzing the solidification cooling curve of GW93 alloy,it can be obtained that the ultrasonic field is applied during the solidification of the alloy,and the solidification start temperature and the solidification end temperature,the early solidification start time and the solidification end time,and the solidification time are shortened.When the ultrasonic power is 1000W,the solidification time is 47.33s,which is 65.37s faster than that of the untreated alloy.Therefore,the application of the ultrasonic field increases the solidification speed and the crystallization rate,and refines the microstructure of the alloy.(4)For GW93 alloy,when the ultrasonic action time is 60s and the ultrasonic power is 1000W,the grain size and microstructure of the alloy and the comprehensive mechanical properties of the alloy reach the optimal value.The comprehensive mechanics of GW93 alloy after heat treatment The performance is optimal and basically meets the needs of the performance of the gearbox housing. |
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