冷却速度对ZM5镁合金凝固组织与性能的影响

摘要

采用温度采集仪测定砂型(含20 mm厚的冷铁和10mm厚的冷铁)、金属型(铜模和钢模)在镁合金凝固阶段的平均冷却速率,分析了冷却速度对ZM5镁合金铸态组织、相组成和力学性能的影响,以获得铸锭晶粒尺寸、抗拉强度、硬度与凝固冷却速度之间的影响关系.研究结果表明,在砂型Ⅲ区(含10mm厚的冷铁)条件下,其冷却速度最慢,为2.94℃/s;在金属型铜模铸造条件下,其冷却速度最快,为7.88℃/s.ZM5镁合金其微观组织主要是α-Mg和第二相Mg17Al12.随着冷却速度的不断提高,镁合金晶粒明显细化,第二相分布更加弥散、均匀,合金的硬度、抗拉强度和伸长率也明显提高.%The average cooling rate in solidification of sand (including 20 mm thick and 10 mm thick chill),and metal (steel and copper mold) is studied by temperature recorder.Analysis the effect of cooling rate on ZM5 magnesium alloy in cast microstructure,phase composition and mechanical properties,in order to obtain the relationship in the grain size,the tensile strength,hardness and solidification cooling rate.The research indicates that the cooling rate is 2.94 ℃/s in the area under the sand Ⅲ (including 10 mm thick chill) conditions;the cooling rate is 7.88 ℃/s in metal copper cold.The microstructure of ZM5 magnesium alloy is mainly α-Mg,andthe second phase is Mg17Al12.With the continuous increase of cooling rate,magnesium alloy grain is refined,thesecond phase distribution is more diffuse,the hardness,the tensile strength and elongation of the alloy hasimproved markedly.