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Abstract The high-temperature deformation of an Mn-Al alloy with a chemical composition of Mn 51 Al 47 C 2 was assessed using hot compression testing at the temperature range of 600–800 °C and the strain rates ranging 0.001 s−1 to 1 s−1. Optical microscopy (OM), scanning electron microscopy (SEM), electron backscattering diffraction (EBSD) and X-ray diffraction (XRD) analyses were implemented to characterize the samples. It was found that during deformation, the τ phase dynamically transformed into γ 2 + β + ε phases and the transformation temperature reduced from the equilibrium value of about 790 °C down to < 750 °C. In such temperature range, considering the lower strength of the produced phases, the dynamic strain-induced phase transformations caused a flow softening in the stress-strain curves. However, deformation at temperatures lower than 700 °C, in the state of τ phase stability, led to dynamic recrystallization which was responsible for flow softening. The standard approach was applied to calculate the processing maps which represented an optimal working region in the temperature range of 650 °C up to 700 °C with the strain rates lower than 0.1 s−1 in order to avoid flow localization and dynamic phase transformations. [ABSTRACT FROM AUTHOR]

High-temperature deformation of Mn51Al47C2 alloy was investigated through the hot compression tests at the temperature range of 750 °C–800 °C and strain rate of 0.001–1 s−1, where due to the dynamical transformation of τ phase to ε phase, an excessive softening occurs in flow curves. The kinetics of dynamic phase transformation is studied by modified Avrami's equation, and the activation energy of deformation was assessed by applying a standard approach on critical and steady-state stress. It was revealed that the deformation activation energy changed as the phase transformation occurred. Moreover, a physically realistic model is proposed to describe the hot deformation flow curve including strain-induced phase transformation behavior of Mn–Al alloy. The comparison of predicted data with measured ones conveys that the developed formulation has a reasonable accuracy to model the flow stress. [ABSTRACT FROM AUTHOR]

• The four-point method was used in conductivity measurements of MnAl alloys. • The magnetization reversal behavior of MnAl alloys was analyzed. • The effect of the ordering on the magnetic behavior in MnAl alloys was studied. The casting Mn 51 Al 47 C 2 alloy were undergone two distinct heat treatment processes, consisting of the heat treatment at 1000 and 925 °C. The process followed by quenching and annealing at 500 °C for 15 min. The low electrical resistivity for the heat treatment stage at 1000 °C (165* 10-4 Ω.m) can be described by the small fraction of the L 1 0 -ordered τ-phase (40 %). But the high resistivity for heat treatment at 925 °C (290.4* 10-4 Ω.m) originates within the large fraction (>95%) of the L 1 0 -ordered τ-phase with space inversion symmetry inhibiting the transport process. The magnetic characterization revealed higher M s , M r and H c along with superior (BH) max for Mn 51 Al 47 C 2 alloy heat-treated at 925 °C. Additionally, the derivative hysteresis loops assign narrow maxima to Mn 51 Al 47 C 2 alloy when containing less amount of the L 1 0 -ordered τ-phase. Also, tracking the magnetization reversal behavior through the Henkel plots display the increasing negative-peak dominated curve for Mn 51 Al 47 C 2 alloy when moving from the as homogenized sample (100% τ-phase) to those heat-treated at 1000 (40% L 1 0 -ordered τ-phase) and 925 °C (>95% L 1 0 -ordered τ-phase), respectively. This highlights the deterioration of the exchange coupling interaction between the grains when dominated with a highly ordered L 1 0 -τ-phase. The trend is best confirmed by the quantitative results gained from recoil loops for demagnetization, reversible and irreversible magnetization curves, indicative of a low degree of exchange interactions when the L 1 0 -ordered τ-phase is dominant. Furthermore, analyzing the nucleation field through the Kondürsky model gives a low value of 0.41 kOe for the alloy in the as homogenized state. This behavior can be attributed to the boosted propagation of the anisotropy field and enhanced magnetic exchange coupling in a structure with dominant regular τ-phase for which the deleterious effects of the interfaces for the L 1 0 -ordered τ-phase can be avoided. [ABSTRACT FROM AUTHOR]