Abstract: High entropy alloy has attracted increasing attentions. However, to enhance the alloy strength often leads to impairment of the ductility, or vice versa. Here we reported a heat treatment approach on AlCrFeNi2Ti0.5 high entropy alloy, which can elevate the strength and ductility simultaneously. An ingot of AlCrFeNi2Ti0.5 weighing 2.5 kg was firstly fabricated by medium frequency induction melting. Then samples from the same height of the bulk ingot were annealed for 6 h at 600, 700, 800 and 1000 °C, respectively. After 1000 °C annealing, an optimal microstructure was obtained by using our approach which can make some precipitation particles distribute homogeneously in the dendrite interior while keep the interdendrite structure as a single solid solution phase. The mechanical test on this AlCrFeNi2Ti0.5 alloy sample showed that, the compressive fracture strength σbc was increased by about 600 MPa and the plastic strain εp was doubled, compared with those of the as-cast sample. Our approach can be readily adapted to large-scale industrial production of high entropy alloys with high strength and ductility by proper annealing treatment.

Key words: High entropy alloy, Heat treatment, Microstructure, Mechanical properties