快速凝固Ml(NiCoMnTi)_5合金的组织结构与电化学性能

Microstructure and Electrochem ical Properties of Rapidly Solidified Alloy Ml( Ni Co Mn Ti)5 S H U K-y., L E I Y.-q., L U G.-l., Y A N G X.-g., Z H A N G S.-k., W A N G Q.d.

本文对比研究了快速凝固和常规熔铸Ｍｌ（ＮｉＣｏＭｎＴｉ）５合金的组织结构和电化学性能。ＳＥＭ和ＸＲＤ分析研究表明，冷却速度较慢的常规熔铸合金为粗大的树枝晶组织，合金中Ｍｎ偏析明显，并且有少量ＴｉＮｉ３第二相生成。但在冷却速度高达１０５～１０６Ｋｓ－１快速凝固条件下，合金的组织转变为细小的柱状晶，合金呈ＣａＣｕ５型单相结构，并使Ｍｎ的成分偏析得到抑制。电化学性能测试结果表明，快凝合金的放电容量比常规熔铸合金稍高，放电电位平台更为平坦，充放电循环稳定性得到显著改善。但快凝过程使合金的起始活化次数增加，高倍率放电性能有所降低。

The m icrostructure and electrochem ical properties of M l( Ni Co M n Ti)5 alloys prepared byboth rapid solidification and conventional induction m elting w ere com paratively investigated. S E M and X R Dstudies show ed that the m icrostructure of conventional cast alloy cooled slow ly from its m elt w as of den drite,w here obvious segregation of M n and trace second phase Ti Ni3 w ere found. How ever,the rapidly solidi fied alloy(cooling at a rate of 105 ～106 Ks- 1) w as found to be in colum nar structure,and contained Ca Cu5type single phase only, M n segregation w as restrained effectively as w ell. Electrochem ical m easurem entsshow ed that the rapidly solidified alloy had higher discharge capacity,m ore flat discharge potential plateauand longer cycle life than induction m elt alloy,but its activation and high rate property degraded. The im proved cyclic stability ofrapidly solidified alloy w as attributed to its com position hom ogeneity and the colum nar structure,w hich show ed a effective resistance to pulverization during absorbing/desorbing hydrogen.