微量元素Sr对AM60B镁合金组织和性能的影响

利用光学显微镜(OM)、场发射扫描电子显微镜(FESEM)、电子万能试验机、数显洛氏硬度计和显微硬度仪研究微量Sr对镁合金AM60B的铸态组织和力学性能的影响。结果表明,添加微量元素Sr可以细化镁合金的晶粒,而不改变基体α-Mg相的枝晶形貌,但可改变γ相的形态和大小,从连续或断续网状、长条状,变为卵石状或颗粒状。Sr对AM60B镁合金的抗拉强度和延伸率的影响具有相似的趋势,即随着Sr含量的增加,合金的抗拉强度和延伸率呈现先升后降的趋势,当Sr含量为0.05%时抗拉强度和延伸率分别达到最大值191.82MPa和4.63%,而洛氏硬度和显微硬度随着Sr含量的增加而增大。AM60B镁合金断裂方式存在着由解理断裂向准解理断裂再向解理断裂转化的模式。

Effect of Trace Element Sr on Microstructure and Properties of AM60B Magnesium Alloy

Effects of trace element Sr on the as-cast microstructure and mechanical properties of magnesium alloy AM60B were studied by optical microscope (OM), field emission scanning electron microscopy (FESEM), electronic universal testing machine, digital display Rockwell hardness tester and microhardness tester. The results show that the addition of trace element Sr can refine grains without change of dendrite morphology of matrix α-Mg phase, but can change the morphology and size of γ-Mg_(17)A1_(12) phase from continuous/discontinuous netlike or strip form to cobble or particulate form. The effect of Sr on the tensile strength and elongation of AM60B magnesium alloy has the similar tendency, i.e. with the increase of Sr content, the tensile strength and elongation of AM60B magnesium alloy are first increased and then decreased. With addition of 0.05% Sr, the tensile strength and elongation reach the maximum 191.82 MPa and 4.63%, respectively, while the Rockwell hardness and microhardness are increased with the increase of Sr content. The fracture mechanism of AM60B magnesium alloy is changed from cleavage fracture to quasi-cleavage fracture to cleavage fracture.