Hierarchical heterostructure AlCr1.3TiNi2 medium entropy alloy with exceptional strength and wear performance at low and intermediate temperatures fabricated by spark plasma sintering

In this study, we explore the mechanical behavior and wear mechanisms in the hierarchical heterogeneous structured AlCr 1.3 TiNi 2 MEA. Tailoring the hierarchy of a heterogeneous structure is affected by eutectic composition, high negative enthalpy and fabrication process (mechanical alloying (MA) and spark plasma sintering (SPS). These heterogeneities can be considered by bimodal distribution of grain size, microscale and sub-microscale B2 particles, tiny Ti rich-BCC phase and L2 1 phase, nano-scaled L1 2 and some L2 1 phases as well as chemical heterogeneity. The AlCr 1.3 TiNi 2 MEA exhibits the highest compressive yield and ultimate compressive strengths which are about 2280 MPa and 2480 MPa at 400 °C. The yield and ultimate compressive strengths are about 2170 MPa and 2296 MPa, as well as 879 MPa and 1060 MPa at RT and 600 °C, respectively. At RT, the specific yield strength value of the alloy is 360 MPa cm 3 /g. The synergy of high hardness and low friction coefficient ( ∼ 0.31) values is achieved for the alloy as a friction-reduced material at RT. Friction coefficient gradually increases to 0.46 at 400 °C and then 0.5 at 600 °C. Specific wear rate increases from 8.8 ∗ 10 −5 mm 3 /N.m at RT to 17.8 ∗ 10 −5 mm 3 /N.m at 400 °C and suddenly decreases to 2.2 ∗ 10 −5 mm 3 /N.m at 600 °C (75 % lower than one at RT). Creation of dense oxide layer can cause higher friction coefficient whereas simultaneously decreases the specific wear rate. The superior synergy of anti-wear and friction-reduced abilities of the AlCr 1.3 TiNi 2 MEA across a wide temperature range results from low friction coefficient and specific wear rate.