Al-containing MAX phase ceramic has demonstrated great potential in the field of high-performance low-voltage electrical contact material. Elucidating the anti-arc erosion mechanism of the MAX phase is crucial for further improving performance, but it is not well-understood. In this study, Ag/Ti₃AlC₂ electrical contact material was synthesized by powder metallurgy and examined by nanoindentation techniques such as constant loading rate indentation, creep testing, and continuous stiffness measurements. Our results indicated a gradual degradation in the nano-mechanical properties of the Ti₃AlC₂ reinforcing phase with increasing arc erosion times, although the rate of this degradation appeared to decelerate over arc erosion times. Specifically, continuous stiffness measurements highlighted the uneven mechanical properties within Ti₃AlC₂, attributing this heterogeneity to the phase’s decomposition. During the early (1–100 times) and intermediate (100–1000 times) stages of arc erosion, the decline in the nano-mechanical properties of Ti₃AlC₂ was primarily ascribed to the decomposition of Ti₃AlC₂ and limited surface oxidation. During the later stage of arc erosion (1000–6200 times), the inner region of Ti₃AlC₂ also sustained arc damage, but a thick oxide layer formed on its surface, enhancing the mechanical properties and overall arc erosion resistance of the Ag/Ti₃AlC₂.

The achievement of chemical diversity and performance regulation of MAX phases primarily relies on solid solution approaches. However, the reported A-site solid solution is undervalued due to their expected chemical disorder and compliance with Vegard’s law, as well as discontinuous composition and poor purity. Herein, we synthesized high-purity Ti₂(Sn_xAl_1−x)C (x = 0–1) solid solution by the feasible pressureless sintering, enabling us to investigate their property evolution upon the A-site composition. The formation mechanism of Ti₂(Sn_xAl_1−x)C was revealed by thermal analysis, and crystal parameters were determined by Rietveld refinement of X-ray diffraction (XRD). The lattice constant (a) adheres to Vegard’s law, while the lattice constant (c) and internal free parameter (z_M) have noticeable deviations from the law, which is caused by the significant nonlinear distortion of Ti₆C octahedron as Al atoms are substituted by Sn atoms. Also, the deviation also results in nonlinear changes in their physicochemical properties, which means that the solid solution often exhibits better performance than end members, such as hardness, electrical conductivity, and corrosion resistance. This work offers insights into the deviation from Vegard’s law observed in the A-site solid solution and indicates that the solid solution with enhanced performance may be obtained by tuning the A-site composition.

Slip casting and subsequent pressureless sintering (PLS) allow the preparation of complex-shaped and large-sized Ti₃AlC₂ components for many potential applications. The behaviors of the suspensions, green compacts, and sintered samples of Ti₃AlC₂ were studied in this paper. The optimized condition of 1 wt% of arabic gum as dispersant at pH = 10 results in a Ti₃AlC₂ suspension for slip casting Ti₃AlC₂ green compacts without macro defects or cracks. The sintering temperature and Al₄C₃ embedding powder are found to dominate the properties of the sintered Ti₃AlC₂ samples. The Ti₃AlC₂ sample sintered at 1450 ℃ for 1.5 h with Al₄C₃ embedding powder reaches the best properties, namely 95.3% relative density, hardness of 4.18 GPa, thermal conductivity of 29.11 W·m^-1·K^-1, and electrical resistivity of 0.39 μΩ·m. The findings in this work may pave the way for the application of MAX phases with large size and complex shape.

New Ag/Ti₂SnC (Ag/TSC) composites with uniform microstructure were prepared by powder metallurgy. The superior wettability between Ag and Ti₂SnC was confirmed with a contact angle of 14°. Arc erosion properties of Ag/10wt%Ti₂SnC (Ag/10TSC) and Ag/20wt%Ti₂SnC (Ag/ 20TSC) contacts were investigated under 400 V/100 A/AC-3 and compared with Ag/CdO contact. The Ag/10TSC contact exhibited comparable arc erosion property to Ag/CdO contact. The fine arc erosion resistance was attributed to the good wettability between Ti₂SnC and Ag, the good heat-conducting property of Ag/10TSC, and the slight decomposition of Ti₂SnC that absorbed part of electric arc energy. The excessive Ti₂SnC significantly decreased the thermal conducting property of the Ag/20TSC composite, resulting in the severe heat accumulation that decomposed Ti₂SnC and deteriorated arc erosion property. The oxidation behavior of Ti₂SnC under high electric arc temperature was also studied and then an arc erosion mechanism was proposed to get a comprehensive understanding on the arc erosion property of Ag/TSC composites.

Ti₂PbC was synthesized for the first time by pressureless reaction synthesis using Ti/Pb/TiC as starting materials at a heating rate of 2 ℃/min and holding at 1370 ℃ for 2 h in a tube furnace protected by Ar atmosphere. The effects of starting powders, heating rates, and holding temperatures on the formation of Ti₂PbC were investigated. It was found that elementary mixture of Ti/Pb/C or higher heating rates fail to form Ti₂PbC. The decreased lattice parameters in the synthesized Ti₂PbC indicated the existence of Pb vacancies in the compound. A reaction mechanism was proposed to explain the formation of Ti₂PbC.