Synthesis of ternary and quaternary MAX phases in Ti/Cr/Nb/V-Al-C system by high energy ball milling and pressureless spark plasma sintering

The search for MAX phase synthesis methods that allow good energy efficiency and phase purity remains
ongoing. In this work, high energy ball milling and pressureless spark plasma sintering were used to synthesize
ternary and quaternary MAX phases from Ti/Nb/V/Cr-Al-C system in a powder form. The powders were
densified in a separate spark plasma sintering process. Synthesized powders and bulks structure were studied
using scanning electron microscope and X-ray diffraction. Chemical composition was determined using energy
dispersive X-ray spectroscopy and carbon and oxygen analyzers. Thermal oxidation and mechanical properties
were assessed using thermogravimetry and nanoindentation. The high energy ball milling and pressureless spark
plasma sintering route allowed fabrication of both ternary and quaternary MAX phase systems, except TiCrAlC
and NbCrAlC. The synthesized MAX phases purity was in the range of 92–98 %, according to Rietveld refinement.
Secondary phases consisted of M-X carbides and M-A intermetallics, as well as aluminum oxide. The highest
hardness and elastic modulus values were observed for Nb2AlC and NbVAlC MAX phases. Thermogravimetric
tests showed limited oxidation rate of MAX phases within 20–900◦C range, except for Ti2AlC, which could be
attributed to increased oxygen content before test. This work presents a beneficial method for fabrication of
relatively phase-pure MAX phases using different M-type elements as precursor materials.