Study On Microstructure And Properties Of The Antiferromagnetic MnNi Based Alloys

Mn-rich MnNi based alloys are a typical antiferromagnetic alloys, which have not yet been fully developed. Therefore, it is practically important to study the properties of MnNi based alloys.In this paper, the internal friction damping capacity, compression pseudoelasticity and corrosion resistance in a simulated solution for marine atmosphere environment of Mn-rich MnNi based alloys have been investigated by means of high-precision multifunctional internal friction apparatus, differential scanning calorimetry(DSC), compression test, X-ray diffraction(XRD), electrochemical workstation and scanning electron microscopy(SEM). The results are as follows:(1) The main internal friction peak of Mn-rich MnNi based alloys is originated from antiferromagnetic transition. To Mn-rich MnNi binary alloys(Mn85Ni15,Mn82.2Ni17.8, Mn80Ni20), with the decrease of Mn content, the antiferromagnetic transition Néel point drops and the internal friction values decrease which means the damping capacity declines. Martensitic transformation happens in the low temperature region of MnNiCu alloys(Mn82.2Ni15.8Cu2,Mn82.2Ni13.8Cu4), and their Néel point decreases with the increase of Cu content, meanwhile the two alloys’ antiferromagnetic transition is close to martensitic transformation which means the damping capacity improves.(2) The Mn-rich MnNi based alloys show pseudoelasticity. The pseudoelasticity capacity of MnNi binary alloys(Mn85Ni15,Mn82.2Ni17.8,Mn80Ni20)increases with the decrease of Mn content(the εrec can be more than 7%). Compared with Mn82.2Ni17.8,the pseudoelasticity capacity of MnNiCu(Mn82.2Ni15.8 Cu2,Mn82.2Ni13.8 Cu4)improves when parts of Ni are replaced by Cu(the εrec of Mn82.2Ni13.8Cu4 can be nearly 9.6%), however, the pseudoelasticity capacity of MnNiCu ternary alloys less obviously improves when the replacement proportion enlarges.(3) The curves of potentiodynamic polarization of Mn-rich MnNi based alloys are similar to each other and the passivation coating forms in the process of anodic polarization. The sensitivity of Mn-rich MnNi binary alloys(Mn85Ni15,Mn82.2Ni17.8, Mn80Ni20) to self-corrosion is reduced, but the corrosion resistance is worse with the increase of Ni content when the alloys are corroded. Compared with Mn82.2Ni17.8,the self-corrosion tendency of MnNiCu(Mn82.2Ni15.8Cu2,Mn82.2Ni13.8Cu4) drops while the corrosion resistance is enhanced with more and more Ni replaced by Cu.(4) In view of internal friction damping capacity, compression pseudoelasticity and corrosion resistance of MnNi based alloys, Mn85Ni15 assumes good damping capacity and corrosion resistance, Mn82.2Ni13.8Cu4 presents the best comprehensive performance.