Characterization of powder metallurgically produced AlCrFeNiTi multi-principle element alloys

In the present work, a multi-principle element alloy (MPEA) with the five base elements Al, Cr, Fe, Ni and Ti in equimolar ratio plus additional elements was produced by powder metallurgy (MPEA5). Thereby, the influence of gentle compositional variations on the resulting material properties was investigated. The chosen MPEA compositions are closely related to conventional alloys (for comparison purposes). The goal is to supplement outstanding properties of existing alloys with MPEA-typical properties. For this purpose, the Al, Cr and Ti contents of the produced MPEA were separately reduced to a level as low as 10 mol%. Thereby, the remaining four base elements stay in equimolar proportion to each other. The starting materials were various prealloyed powders and elemental powders. The MPEAs were produced by combining and mechanical alloying of these powders and then were sintered by hot isostatic pressing. From thermodynamic calculation of stable phases it was predicted that the microstructure of MPEA5 consists of BCC- and Heusler-phases. Altering the chemical composition of MPEA5 by lowering the amount of Cr or Ti only resulted in minor changes of distributed phases. Calculation showed the stabilization of the C14_Laves phase (\(\hbox {Fe}_{2}\hbox {Ti}\)) with decreasing amount of Al. Microstructure analysis of the MPEAs via scanning electron microscopy, energy dispersive X-ray spectroscopy and X-ray diffraction confirmed the predicted phases. Properties analysis of the MPEAs was conducted via measurement of density and hardness tests. MPEA5 showed a measured density of \(6.33 \pm 0.32\) g/cm\(^3\) which coincides well to the predicted density via CALPHAD. MPEA5 reached a remarkable hardness of 839 HV10, which is at least 40% higher than the hardness of the established alloys L718 and W722, even if these were precipitation hardened. The reasons for the high hardness were the observed fine dispersion of the phases and the strong solid solution strengthening in MPEA5 and its modifications. Furthermore, it has been verified that a decrease of the Al amount in MPEA5 led to the formation of the hard C14_Laves-phase and an increase in hardness of the composition up to 912 HV10.