TbDyFe中稀土元素的烧损对组织和性能的影响

Effect of Rare Earth Elements Burning Loss on Microstructure and Properties in TbDyFe

在模拟实验低真空环境下,将Tb,Dy及Fe合金元素经过熔炼、定向凝固、热处理后,制备了Tb_(0.27)Dy_(0.73)Fe_(1.91)合金棒。测试合金棒的磁致伸缩性能,研究材料的组织结构,分析组织中缺陷产生的原因。结果表明:在低真空环境下,大量的孪生枝晶片层和普通孪晶组织产生,其中片层状孪晶具有良好的压磁效应和力学性能,而普通孪晶的产生对材料磁致伸缩性能产生不利影响。合金基体主要相为REFe_2与REFe_3耦合相,烧损导致合金的成分偏离,造成包晶REFe_2相和初生REFe3相的耦合生长。与此同时,存在由于热应力产生的微裂纹和稀土元素偏聚烧损后产生的孔洞。这些组织和缺陷对TbDyFe合金棒的磁致伸缩性能和力学性能产生不利影响。

In order to simulate low vacuum experimental environment,Tb_（0.27）Dy_（0.73）Fe_（1.91） alloy round bars were prepared through melting with Tb,Dy and Fe elements,directional solidification and heat treatment in low vacuum environment.The magnetostriction of the alloy rods was tested.The microstructures and the causes of defects in the alloy were investigated.The results indicate that under the low vacuum experimental environment,there are plenty of twin dendritic lamellar microstructures and ordinary twin microstructures are generated in alloy,among which the mechanical properties and＂jump＂effect of twin dendritic lamellar structures are good,while the ordinary twins are bad to the magnetostrictive property in the alloy.REFe_2 and REFe_3coupling phase is the main phase in the matrix,the burning loss of rare earth elements lead variations in chemical composition,resulting coupling growth with REFe_3 phase and REFe_2 phase.The thermal stress and the burning loss of rare earth elements segregate at grain boundaries resulting in the presence of micro-cracks and micro-holes.These microstructures and defects generate bad impact on mechanical properties and magnetostriction of TbDyFe alloy rods.