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用正电子寿命谱测量方法研究了5种不同化学成分的近等原子比NiTi合金中的微观缺陷和自由电子密度。结果表明,当Ni原子和Ti原子形成NiTi合金时部分3d电子被局域化而形成共价键,导致合金中参与形成金属键的自由电子减少。近等原子比的NiTi合金中的基体和缺陷处的自由电子浓度均随Ni含量的增加而改变,并且当Ni含量为51 at%时达到最大值。研究还发现Ni51Ti49合金含有最少的缺陷,从而有助于马氏体相变的发生,这可能成为Ni51Ti49合金具有最好的形状记忆效应的一个原因。
The positron-to-atomic ratio NiTi alloys of five different chemical compositions were studied for their microscopic defects and free electron densities using positron lifetime spectroscopy. The results show that when Ni atoms and Ti atoms form NiTi alloys, part of the 3d electrons are localized to form covalent bonds, resulting in the reduction of free electrons involved in the formation of metal bonds in the alloy. The free electron concentration in the near-atomic ratio NiTi alloy matrix and defects both changed with the increase of Ni content, and reached the maximum when the Ni content was 51 at%. The study also found Ni51Ti49 alloy contains the least defects, which contribute to the occurrence of martensitic transformation, which may become Ni51Ti49 alloy one of the best shape memory effect.