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.

Abstract

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.