Explore of NiMn-base meta-magnetic shape memory alloys

Heusler合金如Ni-Mn-Ga和Ni-Mn-In合金作为铁磁性形状记忆合金和变磁性形状记忆合金受到了广泛的关注。在NiMn-B2相到Ni 2 MnX-L21相的成分范围内，合金在高温下形成bcc基有序结构的固溶体。这种bcc基有序相转变为具有独特磁性的马氏体相。对于含有Al、Ga、In、Sb等准金属族的合金，bcc有序结构的稳定性已经研究得很好，但对于Si、Ge、Pb、Bi等准金属族的合金，bcc有序结构的稳定性还没有得到明确的研究。本文制备了Ni_（59）Mn_（50-x）X_x（X：Si，Ge，Pb，Bi）合金，并研究了这些合金在850 ℃ ~ 850 ℃温度范围内的相稳定性。C到1000 C进行了调查。添加少量Si和Ge的合金表现为马氏体结构，Si和Ge在NiMn-B2结构中的固溶度分别为4at%和7at%。Ni 50 Mn 35 Si 15和Ni 50 Mn 35 Ge 15合金均为单相结构。但这些合金的晶体结构。2相为Ni_3Mn_2Si_2结构，而不是bcc结构的固溶体相。在Ni-Mn-Ge系中，新发现了1，2，T。在含有Pb和Bi的合金中，这些元素在NiMn-B2相中的溶解度小于1at%，马氏体相的结构为2 M结构

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