Preparation of the AlTiNiCuCox system high-entropy alloys and structural analysis

Abstract: This study aimed to explore and develop a new material with high cost-effectiveness, excellent strength, light weight, high hardness, great wear resistance, corrosion resistance, and favorable oxidation resistance. Structural analysis suggested that, with the change in Co addition amount, the surface morphology and structure of the alloy system changed. XRD analysis indicated that, the alloy system was the FCC+BCC mixed structure. In addition, metallographical demonstrated that, with the increase in Co content, the dendritic crystal transformed from big block to dendritic structure, then to snowflake, gradually to petal-like, and finally to petal shape. SEM-EDS analysis revealed that, Cu element was enriched in interdendritic site, while Ti, Ni, Al and Co elements were enriched in dendrite. Besides, TEM and TEM-EDS analysis indicated that, there was nano-size precipitate of small particles in the Cu-enriched block region, along with dislocation; further, there was twin structure inside the dendrite, as well as the second phase with different morphology, and the second phase showed coherency with the matrix. The above analysis suggested that, the intercrystalline structure was the Cu-enriched phase of FCC structure; the internal matrix of grain was the NiTi and TiCo phases of BCC structure; and the second phases inside the grain were the AlCu2Ti,AlNi2Ti,AlCo2Ti and CuNi phases of FCC structure. Taken together, the AlTiNiCuCox system novel alloys have changed phase structures and phase types of the alloy system.