Study On Solidification Structure And Growth Characteristics Of ZL205A Alloy By Alternating Magnetic Field And Vacuum Counter-pressure Co-casting

ZL205A alloy is a typical high strength and toughness Al-Cu alloy.However,due to its poor casting properties and coarse grain,casting defects such as shrinkage cavity and shrinkage are easily produced in the casting,which seriously limits the full use of its excellent mechanical properties.Vacuum counter-pressure casting process has good filling and solidification mechanics conditions,which can obtain dense aluminum alloy castings.The combination of electromagnetic casting technology and vacuum counter-pressure casting technology provides a new idea for obtaining high performance aluminum alloy with dense structure and fine grained.By applying alternating magnetic field during vacuum counter-pressure casting,the effects of excitation current and solidification pressure on the solidification structure and growth characteristics of ZL205 A alloy by alternating magnetic field and vacuum counter-pressure co-casting were studied,and the mechanism of solidification and refinement of aluminum alloys under cooperative field was discussed.The results show that with the increase of the excitation current,the relative density and the average grain size of the co-cast ZL205 A alloy increase first and then decrease.When the excitation current is 10 A,the relative density reaches a peak,and the higher the solidification pressure,the higher the relative density.When the excitation current reaches 15 A,the average grain size is the smallest.At this point,as the solidification pressure increases,the average grain size decrease gradually,while the tensile strength and elongation increase accordingly.Under the conditions of 15 A of excitation current and 350 KPa solidification pressure,the synergetic effect of alternating magnetic field and solidification pressure is the best.The relative density of ZL205 A alloy increased to0.9918.The average grain size of primary ?(Al)reaches a minimum value of 78.25?m,a decrease of 13.89% compared with gravity casting,and preferred growth orientation is impaired.The tensile strength and elongation reached the maximum values of414.39 MPa and 3.71% respectively,and the fractured dimples of the specimens were significantly increased compared with gravity casting and vacuum counter-pressure casting.Therefore,the technology of co-casting with alternating magnetic field and vacuum counter-pressure can obtain ZL205 A alloy castings with better solidification structure and mechanical properties.Further more,it can also provide theoretical guidance and technical support for vacuum counter-pressure casting high qualitylarge-scale complex thin-walled aluminum alloy precision castings.