Mechanical alloying spark plasma sintering and characterisation of Fe Ni nanopowders

Abstract

Research on nanoscale materials has been steadily increasing. Nano-structured magnetic materials exhibit new and interesting physical and magnetic properties, which cannot be found in the bulk. The study of the sintering of iron nickel alloy in the conventional method is available, whereas, studies on the spark plasma sintering of an iron nickel alloy are unavailable. Therefore, research is required to find whether the variation of magnetic properties is caused by the particle size or the grain size or the impurities of alloys, and also to study the temperature required for spark plasma sintering. The present study is focused on investigating the effect of mechanical alloying and spark plasma sintering of 40, 50 and 75wt.% Ni-Fe alloys with varying milling hours, grain size, particle size and alloying element, on the mechanical and magnetic properties. In general, an increase in the nickel content causes a decrease in the value of Mr beyond 2 hours of milling. It could be observed from the two hours milled sample that the values of Mr drastically increase from the initial values of iron and nickel. It is observed from all the SPS samples that the value of the coercive field is lower than that of the powder samples. It is observed that the value of hysteresis loss at intermediate grain and particle size is high. And fine and coarse grain sizes and when the particle size is either large or small it is low. The change in the values of squareness decreases with the decrease in the grain size. The values of squareness are observed to be dependent on the grain size. High values of squareness are observed when the grain size is 215 to 150 nm. The values of squareness are observed to be dependent on particle size when these are 16 to 13 and#1048656;m. A high squareness value is found in the case of 40wt.% Ni-Fe, 32 hour milled SPS sample. Its grain size is measured as 425 nm. newline