Alternative Thermal Cycling Treatment to Produce Abnormal Grain Growth in FeMnAlNi Alloys: Study of Composition Variations and Effects on the Relative Phase Stabilities

An alternative method to obtain abnormal grain growth in Fe–Mn–Al–Ni system is presented. A crucible is used to control the cooling speed of the samples from 1200 °C enabling the nucleation of the equilibrium fcc phase. This fcc structure leads to an abnormal grain growth after heating to 1200 °C, temperature at which the bcc phase is stable. In this way, crystals with a mean diameter of 18 mm are obtained after 4 thermal cycles which take approximately 2 h. Additionally, precise composition measurements using neutron activation allowed the detection of a decrease in Mn content after each thermal cycle. Using electrical resistivity measurements, the effect of the variation of Mn content on the relative phase stability between the bcc austenite and the fcc martensite has been observed and is discussed here.