固溶时效对Mg-12Li-3Al-xNd合金组织和硬度的影响
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摘要
为了改善Mg-12Li-3Al合金的力学性能,制备了Mg-12Li-3Al-xNd合金,并对其进行了固溶+自然时效处理。结果表明,Mg-12Li-3Al-xNd合金的铸态组织为单相β(Li),并且含有Al4Li9、MgLiAl_2、Al Li等相,随着Nd含量的增加,Al-Nd金属间化合物由针状Al_(11)Nd_3变为颗粒状Al_2Nd;该合金经过固溶+自然时效处理后在晶界附近析出强化相MgLiAl_2,Al_2Nd的形态由颗粒状变为椭球状,并且铸态下生成的Al Li平衡相完全固溶到β(Li)基体中。此外,稀土元素Nd延缓了Mg-12Li-3Al-xNd合金的过时效析出效应,MgLiAl_2析出相与母相的错配度较大,有较强的硬化效应,有利于合金在室温保持较好的稳定性。因此,固溶+自然时效处理提高了Mg-12Li-3Al-xNd合金的硬度。
In order to enhance the mechanical properties of Mg-12 Li-3 Al alloy,Mg-12 Li-3 Al-xNd alloy was prepared and treated by solid solution-natural aging. The results show that the as-cast microstructure of Mg-12 Li-3 Al-xNd alloy is single-phase β( Li) and comprises Al4 Li9,MgLiAl_2,AlLi. With the increase of Nd content,Al-Nd intermetallic compounds change from needle like Al_(11) Nd_3 to granular Al_2 Nd. After solid solution-natural aging treatment,strengthening phase MgLiAl_2 precipitates near the grain boundary,and the morphology of Al_2 Nd varies from granular to ellipsoid,as well as the AlLi equilibrium phase produced in the as-cast state is completely dissolved into the matrix of the β( Li). In addition,the rare-earth element Nd delays the over aging precipitation effect of Mg-Li-Al alloy. The mismatch degree of MgLiAl_2 precipitated phase with the matrix is larger and MgLiAl_2 has strong hardening effect,which is beneficial to the good stability of the alloy at room temperature.Therefore, solution-natural aging treatment has improved hardness of Mg-12 Li-3 AlxNd alloy.
In order to enhance the mechanical properties of Mg-12 Li-3 Al alloy,Mg-12 Li-3 Al-xNd alloy was prepared and treated by solid solution-natural aging. The results show that the as-cast microstructure of Mg-12 Li-3 Al-xNd alloy is single-phase β( Li) and comprises Al4 Li9,MgLiAl_2,AlLi. With the increase of Nd content,Al-Nd intermetallic compounds change from needle like Al_(11) Nd_3 to granular Al_2 Nd. After solid solution-natural aging treatment,strengthening phase MgLiAl_2 precipitates near the grain boundary,and the morphology of Al_2 Nd varies from granular to ellipsoid,as well as the AlLi equilibrium phase produced in the as-cast state is completely dissolved into the matrix of the β( Li). In addition,the rare-earth element Nd delays the over aging precipitation effect of Mg-Li-Al alloy. The mismatch degree of MgLiAl_2 precipitated phase with the matrix is larger and MgLiAl_2 has strong hardening effect,which is beneficial to the good stability of the alloy at room temperature.Therefore, solution-natural aging treatment has improved hardness of Mg-12 Li-3 AlxNd alloy.
引文
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[3]杨云龙,曾建民. Ce对铸态Mg-Li-Al-Ca合金在NaCl溶液中腐蚀行为的影响[J].铸造技术,2018,39(5):960-962.
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[8]李瑞红,蒋斌,陈志军,等.超轻Mg-Li-Al系变形镁合金挤压板材的组织及性能[J].中国有色金属学报,2016,26(1):31-36.
[9]陈昭运,余春,李志强,等.挤压Mg-Li-Zn-Ce-Y-Zr合金的热变形行为[J].稀有金属材料与工程,2011,40(1):91-95.
[10]马洪波,赵平. Y和混合稀土对Mg-Li-Al合金力学性能的影响[J].热加工工艺,2008,37(2):34-37.
[11]刘滨,张密林. Ce对Mg-Li-Al合金组织及力学性能的影响[J].特种铸造及有色合金,2007,27(5):329-331.
[12]卫爱丽,刘兴海,张焜禹,等.复合添加Si、Nd元素对Mg-11Li-3Al合金组织与力学性能的影响[J].稀有金属材料与工程,2016,45(4):990-996.