ABSTRACTMechanical properties of E21 (Mn, Fe)3AlC-base alloys were investigated. The E21 crystal structure is closely related to L12, and thereby E21 compounds are expected to exhibit superior properties similar to those of the L12 Ni3AL. Nominal compositions are fixed to be 60mol%(Mn, Fe)-20mol%A1–20mol%C. Alloys were prepared by mechanical alloying and hot pressing. ICP chemical analysis, X-ray diffraction analysis, scanning electron microscopy and electron probe microanalysis were carried out for alloy characterization. Mechanical properties were evaluated by Vickers hardness tests at room temperature (RT) and compression tests from RT to 1273K. Strain rate dip tests were also carried out. It is found that most alloys are composed of two phases of E21 as the primary phase and graphite as the precipitates, and that the volume fraction of graphite increases with increasing Fe content. Hardness and 0.2% flow stress at RT are raised with increasing Fe content. At RT, 0.2% flow stress and fracture strength of Fe3A1C alloy used are 2.9GPa and 3.4GPa, respectively. An alloy containing 40%Mn-20%Fe shows weak positive temperature dependence of strength at 700–800K, similar to the observation in some Co3AIC alloys. Moreover, work-hardening coefficient of all alloys shows strong positive temperature dependence below 700K. These results suggest the occurrence of K-W related mechanism for plastic deformation in these alloys.
Ceramic/Metal Composites with Positive Temperature Dependence of Thermal Conductivity
