A study of the magnetic properties and the structures of the wear-resisting magnetic head materials

Based on the hard permalloy Ni-Fe-Nb, with an addition of 1.1% Al or 2% Mo-0.5% Al, the magnetic and mechanical properties and the structures of the alloys after various heat treatments have been investigated. Optimum magnetic properties, high mechanical hardness and high electric resistivity of the two categories of alloys have been obtained. From transmission electron microscopy and X-ray diffraction studies, it is noted that modulated structures have been developed in these two categories of alloys. The process of the growth of the modulated structure in Ni-Fe-Nb-Al has been studied in detail, the pre-precipitating phase γ\´ (Ni3(Al,Nb)) occurs periodically along the directions during the early stage of the transformation, coherent with the matrix. With the time of aging increased. the precipitating γ\´- phase segregates on the parallel lamellae, accompanied with a decrease of hardness. The precipitated grains arranged themselves regularly along the and directions. As the grains of γ\´-phase grow gradually, the alloy is strengthened and the hardness again increases. These two categories of alloys can be cold rolled into sheets of different gauges of thickness, suitable for the use as recording head materials.