Study Of WE43A Magnesium Alloy Segregation

WE43A magnesium alloy,which have excellent Tensile,Creep and fatigue performance,is often used to product aircraft castings with complex structure.When the alloy used for the production of some large castings,due to huge volume,huge size change and complex structure,the cooling rate is uneven and slowly.Under the influence of cooling rate and the gravity,the alloy produce serious macrosegregation and microsegregation in the casting process.It is necessary to analyze the causes of segregation and provide effective technological measures to reduce or eliminate these defects.It has great significance to solve practical problems of WE43 A magnesium alloy.To WE43A magnesium alloy,there are two reasons for the generation of macrosegregation.First,because of uneven cooling,rapid cooling section reaches the eutectic temperature which precipitates a large number of second phase compound.Second,slowly cooled alloys cause Rare Earth Elements,which is much greater than the relative atomic mass of magnesium,move down.Thus,Alloy creats serious macrosegregation.The experiment explore how the cooling rate and the gravity influence the segregation of WE43A magnesium alloy by sand mold with a chill and common sand mold.The study found that cooling rate and the gravity influence the segregation of rare earth elements in one chill casting,the segregation exist in the horizontal direction and the direction of gravity.In this case,the cooling rate is dominant,degree of segregation is greater in the horizontal direction.The percentage range of Y?Nd?Gd?Zr is 0.91%?0.26%?0.13%?0.08%.Sand mold have the cooling rate with uniform distribution so that the segregation is only influenced by gravity.The percentage range of Y?Nd?Gd?Zr is 0.83%?0.49%?0.07%?0.02%?Solution treatment have a significant impact on macrosegregation and microsegregation of WE43A magnesium alloy.When solution treatment is under the conditions of 520?×24 h,the second phase in grain boundaries is almost completely disappeared,which solve the microgregation of WE43A magnesium alloy.For macrosegregation,the influence of solution treatment is limited.