Effect Of Physical Field On Solidified Structure And Mechanical Properties Of ZA27 Alloy

ZA27 alloy as a new high-aluminum,high-strength and wear-resistant zinc alloy,compared with traditional sand casting zinc alloy,the mechanical properties have been improved and is applied widely.However,under the condition of ordinary gravity casting,because ZA27 alloy has a wide crystallization temperature range(110?),so,the solidified structure of the alloy tends to form coarse primary dendrites,and produce the shrinkage cavity and porosity defects and dendrites segregation extent increase,which reduces its properties and limits its practical application.Grain refining technology of physical field treatment has been widely concerned because of its simple operation,green pollution-free,and excellent grain refinement effect.In order to further improve solidification structure and mechanical properties of ZA27 alloy,the effect of different physical field treatment on solidification microstructure and mechanical properties of ZA27 alloy were studied in this paper.The major conclusions are as follows.1)After being treated by a single physical field or compound physical field,the solidification structure and mechanical properties of ZA27 alloy have greatly improved.Primary phase of the alloy transforms from coarse dendrites to fine equiaxed dendrites or strips,the copper rich phase transforms from continuous network structure to broken net strip distribution,and the compound treatment of physical field has better effect on solidification structure and mechanical properties of the alloy than the single physical field treatment.2)Under the condition of treatment of pulsed magnetic field,in the range of 0~300V,with the increase of pulse voltage,the primary phase of the alloy is refined gradually and the compressive strength of the alloy is increased gradually,and the highest compressive strength of the alloy is increased by 39.6% compared with the alloy without treatment.In the range of 1~10Hz,with the increase of pulse frequency,the primary phase of the alloy is refined gradually and the compressive strength of the alloy is increased gradually.In the range of 490~580? or 20~400?,with the increase of pouring temperatur or mold temperature,the primary phase refines at first and then coarsens,turning points is 520? and 200?.As a whole,the compressive strength of the alloy is increased gradually.3)In the range of 0~900W or 0~90s,with the increase of ultrasonic power or treating time,the primary phase of the alloy refines at first and then coarsens,and mechanical properties of the alloy increases at first and then decreases,turning points is 700 W and 30 s.Tensile strength and elongation of the alloy are increased by up to 1.43% and 114%,respectively,compared with the alloy without treatment.In the range of 520~610?,with the increase of vibration temperature,the primary phase of the alloy is coarsened gradually,but the tensile strength and elongation of the alloy is increased gradually.4)Under the condition of treatment of mechanical vibration field,in the range of 0~300V,with the increase of amplitude voltage,the primary phase of the alloy is refined and compressive strength of the alloy is increased gradually,and the highest compressive strength of the alloy is increased by up to 26.4% compared with the alloy without treatment.In the range of 1~75Hz,with the increase of vibration frequency,the primary phase of the alloy is refines at first and then coarsens,the turning point is 50 Hz,and the compressive strength of the alloy is increased gradually.In the range of 490~580?,with the increase of pouring temperature,the primary phase of the alloy is refines at first and then coarsens,the turning point is 520?,but the compressive strength of the alloy is increased gradually.In the range of 200~400?,with the increase of mold temperature,the primary phase of the alloy is refined,but the compressive strength of the alloy is increased gradually.5)Under the condition of compound treatment of ultrasonic and pulsed magnetic field,in the range of 490~580? or 20~400?,with the increase of vibration temperature or mold temperature,the primary phase of the alloy is refines at first and then coarsens,the turning points is 520? and 200?,respectively.Under the condition of compound treatment of mechanical vibration and pulsed magnetic field,in the range of 0~300V,with the increase of pulse voltage,the primary phase of the alloy is refined gradually.In the range of 1~10Hz,with the increase of pulse frequency,the primary phase of the alloy is refines at first and then coarsens,the turning point is 5Hz.In the range of 490~580? or 20~400?,with the increase of pouring temperature or mold temperature,the primary phase of the alloy is refines at first and then coarsens,turning points is 520? and 200?.Under the condition of compound treatment of ultrasonic and mechanical vibration field,in the range of 490~580 ? or 20 ~ 400 ?,with th increase of vibration temperature or mold temperature,the primary phase of the alloy is refines at first and then coarsens,turning points is 520? and 200?.Under the condition of compound physical field treatment,the mechanical properties of the alloy change the same as the solidification structure.6)Under the condition of different physical field treatment,the solidification structure,mechanical properties and corrosion properties of the alloy have been improved to different degrees.The compound physical field treatment has the best effect on the properties of the alloy.In the compound physical field treatment,the compound treatment of pulsed magnetic field and mechanical vibration has the best effect on the properties of the alloy,the tensile strength and elongation of the alloy are increased by up to 27.8% and 74.5%,meanwhile,the friction coefficient and corrosion rate of the alloy are reduced by up to 17.5% and 35.7%,respectively,compared with without treatment.