摘要
通过成分分析、组织观察及力学性能测试等手段,研究了微量Al对Mg-Gd-Y-Nd-Zr合金铸态组织及室温力学性能的影响,分析了合金中相的组成,成分的沉降规律以及合金的断裂方式。结果表明,铸态Mg-Gd-Y-Nd-Zr镁合金主要由α-Mg基体和共晶组织构成,晶粒近似呈等轴状,晶粒尺寸约为40μm,铸锭轴向不同位置成分偏差较小,晶粒尺寸较为均匀;添加微量Al后成分分布发生明显变化,顶部及底部的晶粒尺寸出现显著差异;同时合金的力学性能也随位置不同而不同,均小于原始Mg-Gd-Y-Nd-Zr镁合金;合金断裂方式主要是沿晶界的脆性断裂,断口中存在明显的二次裂纹。添加Al后,与RE形成Al2RE相,与Zr形成Al3Zr相,液态即形成的大密度Al2RE及Al3Zr相在熔体中沉降,使得元素分布不均,顶部Zr含量明显减小,造成晶粒显著增大;Al2RE与Al3Zr相的存在降低了合金塑性,恶化铸态组织,导致合金发生沿晶脆性断裂。
Abstract. Influences of trace A1 on as-cast microstructures and mechanical properties of Mg-Gd-Y-Nd-Zr alloy were investigated at room temperature by XRD （X-ray diffraction）, SEM （scanning electron microscope） and tensile testing. The phase constituent, deposition change of the composition and fracture mode of the alloy prepared were analyzed. The results show that rheas-cast Mg-Gd-Y-Nd-Zr magnesium alloy is mainly composed of α-Mg matrix and equiaxed eutectic phase with the size of 40 μm approximately. Meanwhile, the composition deviation of ingot in axial is very low, and grain size is uniformly distributed in the ingot. The composition distribution exhibits apparently changes after adding trace A1, and difference of the grain size between the top and bottom appears remarkably. In addition, the mechanical properties of the alloy with trace Al are varied with locations and less than those of the Mg-Gd-Y- Nd-Zr. Alloy fracture mode is mainly characterized by brittle fracture along the grain boundary with obvious secondary cracks. With Al addition, AI2RE and AI3Zr phases can be observed in the alloy, resulting in the heterogeneous distribution of composition in the melt as a result of deposition and leading to the great coarseness of the grain size because of the decrease of Zr content at the top. Due to the generation of Al2RE and Al3Zr phases, as-cast microstructure is deteriorated and elongation is decreased, and alloy crack is characterized by brittle fracture.
出处
《特种铸造及有色合金》
CAS
CSCD
北大核心
2014年第3期322-325,共4页
Special Casting & Nonferrous Alloys
基金
国家重点基础研究发展计划(973计划)资助项目(2013CB632202)
关键词
稀土镁合金
凝固偏析
组织分析
力学性能
Rare Earth Magnesium Alloy, Solidification Segregation, Structure Analysis, MechanicalProperties
