Abstract:AM50-4%(Zn,Y) alloy with a Zn/Y mole ratio of 6:1 was subjected to thermal analysis, and the results were used for designing a two-step progressive solution treatment process. The effects of solution and aging treatments on the microstructure and mechanical properties of the AM50-4%(Zn,Y) alloy were investigated using OM, XRD, SEM/EDS, TEM, tensile test and hardness test. The experimental results demonstrated that the two-step progressive solution treatment could make the Φ and β phases sufficiently dissolve into the matrix which possessed higher supersaturated degree of the dissolved solute compared with the one-step solution treatment. This resulted in a certain enhancement of the precipitation strengthening effect during the subsequent aging process. The precipitation of the Ф phase had a greater impact on the comprehensive mechanical properties of the alloy than β phase precipitation when the aging treatment was performed at 180 °C. The peak aging strength of the AM50-4%(Zn,Y) alloy which was subjected to the two-step progressive solution treatment process (345 °C for 16 h and 375 °C for 6 h) was obtained after the aging treatment at 180 °C for 12 h.

Key words: AM50-4%(Zn,Y) alloy; thermal analysis; solution; aging treatment; microstructure; strengthening mechanism