Evolution of microstructure and defect structure in L10-ordered manganese aluminide permanent magnet alloys

Defects produced in massively transformed L10-ordered τ-MnAl have been characterized by detailed TEM studies. The defect population in massive τ-MnAl comprises arrays of overlapping octahedral stacking faults, {111}-conjugated microtwins, thermal antiphase boundaries and dislocations. The genesis of these defects has been attributed to atomic attachment faulting on {111}- and {020}-type facets of the essentially incoherent growth interface between the parent and product phases. The features of the defect genesis in τ-MnAl are discussed with respect to the role of atomic level processes at solid-state transformation interfaces in general and growth interfaces in massively transforming materials systems in particular.