Abstract

The impact of lanthanum addition on the microstructural changes and mechanical characteristics of Mg–9Li–3Al + xLa alloys are studied. The alloys are fabricated through a liquid metallurgy route involving stir casting by an electrical resistance furnace. The microstructural analysis showed that the as-cast alloys primarily comprises of α-Mg and β-Li phases. Irregular distribution of Al–Li lamellar and some granular fragments MgLi₂Al observed over the magnesium-rich α-phase and lithium-rich β-phase. The influence of lanthanum addition to the alloy system leads to grain refinement by forming Al₁₁La₃ and Al₄La intermetallics. Among the series of cast alloys, the Mg–9Li–3Al–1La alloy exhibits excellent ultimate tensile strength—178 MPa with 10.2% elongation. Addition of 1.5 wt% La and beyond tends to coarsen the grains leading to a reduction in mechanical strength. Hot extruded Mg–9Li–3Al–1La alloy exhibited more refinement in the microstructure and breakdown of intermetallic (Al₄La and Al₁₁La₃) is observed. A significant improvement in the UTS values around 39% displayed by the Mg–9Li–3Al–1La alloy extruded at a ratio of 25:1.

Graphic Abstract

中文翻译：

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镧对Mg-9Li-3Al合金晶粒细化和力学性能的影响

摘要

研究了镧对Mg-9Li-3Al + xLa合金组织和力学性能的影响。合金是通过液体冶金方法制造的，包括通过电阻炉进行搅拌铸造。显微组织分析表明，铸态合金主要由α-Mg和β-Li相组成。在富镁的α相和富锂的β相上观察到Al–Li层状晶体和一些颗粒碎片MgLi ₂ Al的不规则分布。镧对合金体系的影响通过形成Al ₁₁ La ₃和Al ₄导致晶粒细化金属间化合物La。在一系列铸造合金中，Mg-9Li-3Al-1La合金具有出色的极限抗拉强度-178 MPa，伸长率为10.2％。La的添加量为1.5重量％以上时，容易使晶粒粗大化，导致机械强度降低。热挤压的Mg-9Li-3Al-1La合金在显微组织上表现出更多的细化，并且观察到金属间化合物（Al ₄ La和Al ₁₁ La ₃）的破裂。Mg-9Li-3Al-1La合金以25：1的比例挤压时，UTS值显着提高了39％。

图形摘要