Explore of NiMn-base meta-magnetic shape memory alloys

Heusler合金如Ni-Mn-Ga和Ni-Mn-In合金作为铁磁形状记忆合金和超磁形状记忆合金受到了广泛的关注。这些合金在高温下形成bcc基有序结构的固溶体，成分范围从NiMn-B2相到Ni2MnX-L21相。该bcc基有序相转变为具有独特磁性能的马氏体相。对Al、Ga、In、Sb等类金属基合金的有序结构稳定性研究较好，但对Si、Ge、Pb、Bi等类金属基合金的有序结构稳定性研究尚不明确。本研究制备了Ni59Mn50-xXx（X: Si, Ge, Pb, Bi）合金，并研究了这些合金在850℃范围内的相稳定性。C到1000。C被调查。添加少量Si和Ge的合金表现为马氏体组织，Si和Ge在NiMn-B2组织中的溶解度分别为4 at%和7at%。Ni50Mn35Si15和Ni50Mn35Ge15合金均表现为单相组织。但是这些合金的晶体结构是。2相具有Ni3Mn2Si2结构，而非具有bcc有序结构的固溶体相。在Ni-Mn-Ge体系中，1、2、T是新发现的。在含Pb和Bi的合金中，这些元素在NiMn-B2相中的溶解度在%时小于1，马氏体相的组织为2M组织

Heusler alloys such as Ni-Mn-Ga and Ni-Mn-In alloys have received much attention as ferromagnetic shape memory alloys and metamagnetic shape memory alloys. These alloys are formed the solid solution of bcc-base ordered structure at high temperature in the composition range from NiMn-B2 phase to Ni2MnX-L21 phase. This bcc-base ordered phase transform to the martensite phase with unique magnetic properties. In the case of alloys with Al, Ga, In, Sb of metalloid groups, the stability of bcc ordered structure have been studied well, but in the case of Si, Ge, Pb, Bi in the same metalloid groups, those are not clarified yet. In this study, Ni59Mn50-xXx(X : Si, Ge, Pb, Bi)was prepared and the phase stability of these alloys in the temperature range from 850. C to 1000. C was investigated. Alloys added small amount of Si and Ge showed the martensitic structure, and the solubility of Si and Ge in the NiMn-B2 structure is 4 at%and 7at%, respectively. Both Ni50Mn35Si15 and Ni50Mn35Ge15 alloys showed the single-phase structure. But the crystalline structure of these alloys is. 2 phase with Ni3Mn2Si2 structure not solid solution phase with bcc ordered structure. In the Ni-Mn-Ge system, 1, 2, T were newly founded. In the case of alloys with Pb and Bi, the solubility of these elements in NiMn-B2 phase is less than 1 at%and the structure of the martensite phase are 2M structure