Effects Of Mechanical Vibration On Microstructure And Mechanical Properties Of Magnesium Alloy Obtained By Expendable Pattern Shell Casting

At present,the demand for complex magnesium alloy precision casting is increased more and more in the aerospace,automobile,electronics and military industries.Lost foam casting technology is a kind of precision casting method for producing complex magnesium alloy which is a combination of lost foam casting and investment casting.In this study,combined with the vanishing mold casting its own characteristics,by means of powder dry sand vibration compaction machine for magnesium alloy solidification process to improve the microstructure and properties of magnesium alloy,don't need to increase other vibration equipment,to achieve the purpose of improving the microstructure and properties of magnesium alloy,provide a economical and effective method.In this paper,the effects of the thickness of the specimen,the pouring temperature,vibration frequency and amplitude on the microstructure and mechanical properties of the cast magnesium alloy are studied.In order to provide theoretical basis and technical support for the practical application of magnesium alloy by expendable pattern shell casting.When there is no vibration,the filling ability of magnesium alloy is poor,with gradually increased of the pouring temperature,the filling capacity has refined,but the effect of improvement is limited.When the mechanical vibration is applied,the filling ability of magnesium alloy has been improved significantly,the filling ability of magnesium alloy is better at lower pouring temperature.With the increase of the mechanical vibration frequency and amplitude,the filling ability of the magnesium alloy has been refined.When the vibration frequency is 100 Hz,amplitude is 1.0mm,compared to non vibration,the filling length and area have both increased 20.6% and 23%.Grain size of simple can be actually refined by mechanical vibration,the primary phase is converted from dendrite by no vibration to medium axial,the beta phase transition from the coarse network distribution by no vibration to the fine and short rod dispersion distribution;and mechanical vibration has refined mechanical properties and density of magnesium alloy significantly.The higher of wall thickness of magnesiumalloy,the higher degree of grain and mechanical properties refinement.Low-temperature casting can obtain the good microstructure of alloy and grain size of simple is smaller,but low pouring temperature makes mechanical vibration take short time on formation of medium axial grain micro.With the increasing of vibration frequency and amplitude,the grain size and mechanical properties of magnesium alloy has obviously refined.But when the frequency is over 100 Hz,there is no positive effect of refinement.When the pouring temperature is 730?,the vibration frequency is 100 Hz,the amplitude is 1.0mm,and the wall thickness of the sample is 40 mm,the refinement of the microstructure is the best,the grain size and shape factor of the primary ?-Mg are 160.4um and 0.79 respectively.Comparing to non vibration,the grain size has declined 51.1% and shape factor has increased 88.1%;the tensile strength,yield strength and brinell hardness has increased53.7%,33.7% and 59.3% respectively.