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Permanent magnets (PMs) based on manganese show significant potential for applications in electric motors and devices as an alternative to Rare-earth PMs (REPMs). The metastable ferromagnetic τ phase of the Mn-Al system has magnetic performance between the REPM Nd-Fe-B magnets and the lower performance ferrite magnets. However, the maximum performance in Mn-Al PMs has not reached its theoretical limit, in part due to challenges in controlling crystalline defects such as anti-phase boundaries (APBs). APBs act as nucleation sites for domain reversal in Mn-Al and negatively affect magnetization by interrupting the L1 0 ordering, placing Mn atoms into AFM-coupled Mn-Mn configurations. In this study, Ab-initio modeling was used to screen ternary elements based on their affinity to segregate to the APB and on their preference for FM configuration. The ternary element addition of 1 at.% Ti lowered the density of APBs as observed in a transmission electron microscope. The 1 at.% Ti addition was observed to improve (BH) max over the base alloy, by preserving H ci and improving M r. It also significantly increased the fraction of twin boundaries in the τ phase. AFM behavior that was observed in the base alloy during T C heating experiments (Néel behavior) and high-field VSM measurements (spin-flop behavior) was effectively suppressed with the addition of Ti. Additionally, the Ti addition thermally stabilized H ci at 550 °C, improving τ phase processability. Other candidate elements, Cr, V, and Zr, were modeled to have similar potential for minimizing APBs when added to Mn-Al. [Display omitted] [ABSTRACT FROM AUTHOR]

The elastic-plastic transition in magnesium alloy Mg-4.5Zn is marked by bursts of deformation. A relatively short exposure time (44 ms) polychromatic transmission Laue experiment is employed to quantify the magnitude and frequency of these events. Abrupt displacement events seen in tracked Laue peaks reflect (mostly) sudden changes in grain orientation that accompany bursts of deformation. Deformation bursts are seen that are co-ordinated amongst nearby grains. The burst rate peaks at the onset of full plasticity. We associate the most significant peak displacement events to twinning events and this is supported by the twinned structures observed using electron microscopy. Bursts were often preceded and followed by a stasis in peak movement. This is interpreted via the hypothesis that twins adopt a particular 'birth size' upon formation and that subsequent growth occurs at a later point. The twin aspect ratio inferred from peak analysis and those evident in the microstructure are coarser than elastic predictions and we employ numerical analysis to show this is likely to be due to concomitant bursts of accommodating lattice dislocations. [Display omitted] [ABSTRACT FROM AUTHOR]