Electro-Magnetic Characteristics Of Ti-50.8at%Ni In Martensite Transition

The electromagnetism properties of TiNi and the influence on the electromagnetism properties of TiNi by temperature induced martensite phase transfor-mation in TiNi sample have been studied. The Relationship between martensite-austenite transformation and the electromagnetism properties of TiNi in a series of Ti-50.8 at% Ni with different strain has been studied.That the TiNi alloy is a kind of semi-metal is proved by measuring the electrical resistance-temperature curves. And the density of free electrons n, which is the most important parameter for the model of metal free electron,hasbeen calculated by trying using the model of metal free electron. Fermi energyεF is computed using the density of free electrons'n', and we have compared these parameters with those parameters of alkali metals.The magnetism of TiNialloy samples has been researched and the M-H curve at 300K is analyzed, in-cluding the paramagnetic phase and the ferromagnetic phase. Using the M-H under in stronger magnetic field condition, the macroscopical susceptibility has been calculated, it isχ= (1.7±0.1)×10-5. It is found that there are only about 0.07% of the crystal grains are ferromagnetic. It indicates that the ferromagnet-ism in TiNi alloy sample is very weak,and Pauli paramagnetic phase is the main phase. It is accordant to the M-H curves. Using experimental result of M-T curve at higher temperatures, Curie Temperature of the TiNi alloy sample is gained by drawing 1/χ?Τcurve, it is Tc=407K.The influences on the electromagnetism properties of TiNi by martensitic -austenitic transformation in TiNi sample have been studied. It is found in the measurement of specific heat and M-T curves at lower temperatures that there is an abrupt drop at 183K in cooling curve and there is an abrupt ascends at 233K in heating curves. The specific heat has a sudden jump at 234K in the heating process.And curves of electrical resistanceρmeasurement show similarchanges. These experimental results indicate that the starting temperatures of martensitic phase transformation is about 184K, the starting temperature of aus-tenitic phase transformation is about 234K. The magnetism of martensitic phaseand austenitic phase are discussed, and it is discovered that at the same tempe-rature, magnetism of austenitic phase is larger than that of martensitic phase. The M-T curves at lower temperatures show the mechanic strain weakens the magnetism of TiNi alloy samples. But when the strain not exceeds 6%, it willnot change the temperature of martensitic-austenitic transformation. The M-T curves at lower temperatures have been analyzed and the abnormal phenomenon in the M-T curves has been explained using basic magnetics theories.In this paper, a method that try to gain the starting temperatures of mart-ensitic-austenitic transformation of TiNi alloy by comparing experimental results of electrics, magnetics, and specific heat measurements have been carried out. The effect on the magnetism of TiNi alloy samples by mechanical strain is in-vestigated and it is found that the mechanical strain weakens the magnetism of TiNi alloy samples.To study and to know the electromagnetism properties of TiNi alloy offer useful information for its further application,and have positive significance for enlarging its utilization.