研究了添加稀土元素的不同高铝含量的变形挤压态镁合金的微观组织和力学性能.结果表明,铝含量的增加,挤压合金晶粒的得到了明显的细化,平均晶粒尺寸为(12±4)μm.挤压态合金的显微硬度高于固溶态合金的显微硬度;随着铝含量的增加,合金的时效硬化行为得到明显的改善.这些主要是由于在挤压过程中晶粒的细化和沿着挤压方向第二相的析出.另外,随着铝含量的增加,合金的屈服强度和抗拉强度也有所提高,分别达到了306和348 MPa.这主要取决于晶粒的进一步细化和析出相体积分数的增加.因镁稀土相和β-Mg17Al12相都为脆性相,铝含量的增加引起析出相体积分数的增加,也同时导致合金的伸长率有所下降.
The microstructure and mechanical properties of extruded Mg-(8,11)Al-Mn-Y-Gd-La alloys were investigated.It is found that the extruded alloy grains can be significantly refined with the increasing of Al content.The average grain size of the alloy is about 12±4 μm.The microhardness of extruded alloys is higher than that of the solid-solution alloys.With the increasing of A1 content,the age hardening behaviors of alloys are evidently improved,which are mostly attributed to the fine grain size and homogeneous eutectic phase formed during the extrusion process.In addition,with the increase of Al content,yield strength and tensile strength of the alloys are raised to 306 MPa and 348 MPa,respectively,which mainly depends on the further grain refining and the increase of volume fraction of precipitating phase.However,as the MgRE (Y-Gd-La) phase and the β-Mg17Al12 phase are both brittle phases,the increase of Al content can lead to the increase of volume fraction of precipitating phase as well as the decrease of the elongation of the alloy.
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