實驗結果顯示，提高第二階段均質化溫度(由470℃提升至480℃)可有效降低7050鋁合金鑄件殘留S相之數量及尺寸，不同第二階段均質化溫度之7050鋁合金經軋延後之T6抗拉強度分別為577MPa (470℃)及583 MPa(480℃)，可知減少殘留S相含量有助於提升機械性質。7050合金經兩階段及三階段均質化處理後，其再結晶溫度均為500℃，抗拉強度則由583 MPa (二階段)提升至592 MPa (三階段)。
In this study the microstructures and mechanical properties of 7050 Al alloys subjected to 2-step and 3-step homogenization treatments were investigated. In the beginning, a two-stage homogenization treatment of 450°C/12h + 470°C/24h was carried out on the 7050 alloy casting. Followed, the second stage temperature of the homogenization treatment was increased to 480°C, and the effect of increasing the second stage temperature upon the residual S phase was examined. In addition, the effect of two-step (450°C/12h+480°C/24h) and three-step (300°C/12h +450°C/12h+480°C/24h) homogenization treatment on microstructures was examined on the 7050 alloy. The homogenized 7050 alloy were hot rolled (430°C/80% thickness) and T6 treated (480°C/1h+120°C/24h) for microstructures and mechanical properties study. For recrystallization temperature study, the homogenized 7050 alloy were hot rolled (430°C /80% thickness reduction) and cold rolled (room temperature/50% thickness reduction). The influence of homogenization treatment on recrystallization temperature were investigated. The experimental results show that increasing the second-stage homogenization temperature of 7050 alloy castings (from 470°C to 480°C) can effectively reduce the amount and the size of S phase partials. After hot rolling and T6 treatment the tensile strengths of 7050 alloy-T6 homogenized at different temperatures was found to be 577 MPa (470°C) and 583 MPa (480°C), respectively, proving the reduction of S phase particles improve the mechanical properties of 7050 series alloys. After the two-step and three-step homogenization treatment, the recrystallization temperatures of 7050 alloys were found to be 500°C, the recrystallization temperatures were unchanged. The tensile strength of 7050 alloy are 583 MPa (two-step) and 592 MPa (three-step).
Keywords: 7050 Al alloy, homogenization treatment, recrystallization temperature