粗镁直接熔炼AZ91D的力学性能及断口分析

为了研究粗镁直接熔炼AZ91D镁合金锭不同位置上的夹杂分布情况,对AZ91D镁合金锭的三个不同取样位置进行了拉伸及冲击试验,通过扫描电子显微镜对拉伸和冲击断口进行了组织形貌上的观察与分析.结果表明:合金锭中间部分的力学性能要明显优于两侧部分,夹杂含量相对于两侧要低; 粗镁直接熔炼的AZ91D镁合金拉伸与冲击断口形貌呈河流状,为脆性断裂.粗镁直接熔炼的合金产生的夹杂物中的主要元素为C、O、Si,并含有少量Fe、K、Ca、S、Cl、Cr等元素; 在夹杂物周围容易出现二次裂纹,夹杂物的数量和种类直接影响着合金的力学性能.

Mechanical properties and fracture surface analysis of AZ91D prepared with direct smelting of crude magnesium

In order to study the inclusion distribution of AZ91D magnesium alloy ingot prepared with direct smelting of crude magnesium, the tensile and impact tests for AZ91D magnesium alloy sampled from three different positions were carried out. The morphologies of both tensile and impact fracture surfaces were observed and analyzed with scanning electron microscope(SEM). The results show that the mechanical properties of the alloy in the middle part of ingot are obviously superior to those in both sides of ingot, and the content of inclusions in the middle part is lower than that in both sides. Both tensile and impact fracture surfaces for AZ91D magnesium alloy prepared with direct smelting of crude magnesium exhibit the river shape pattern, indicating the occurrence of brittle fracture. The main elements in inclusions for the alloy prepared with direct smelting of crude magnesium are C, O and Si, and a few amount of such elements as Fe, K, Ca, S, Cl and Cr also exist in the inclusions. The secondary cracks will easily form around the inclusions. Furthermore, the type and amount of the inclusions will directly affect the mechanical properties of the alloy.