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摘要: 對鑄態合金進行了均勻化處理、擠壓、固溶處理和時效處理，通過分析合金的化學成分，觀察合金在不同狀態的顯微組織及析出相透射電鏡(TEM)形貌，測試合金在熱處理后的硬度和拉伸性能，研究了向7056鋁合金中加入質量分數0.2%的Sc對合金組織和性能的影響.實驗結果表明，Sc元素的加入可以明顯細化組織晶粒，鑄態晶粒由100~500 μm下降到50 μm左右；Sc元素的加入對合金的塑性有大幅度提高，時效處理后，合金的斷后伸長率從10.82%增加到了13.60%；但屈服強度卻由668 MPa下降到657 MPa.通過綜合計算晶粒大小、析出相強化等因素，詳細分析了Sc元素加入引起7056鋁合金峰時效態屈服強度下降的原因.理論計算顯示，向合金中加入質量分數0.2%的Sc元素時，峰時效處理后，合金的強度值會下降12.005 MPa，與試驗值11 MPa接近.研究得到7056鋁合金最佳的單級時效制度為120℃+16 h，峰值硬度和強度為195.2 HV和714 MPa，此時合金中主要強化相為圓盤狀和短棒狀的MgZn2相，大小約為4~6 nm，同時存在球狀的Al3Zr相，大小約為20 nm.Abstract: Al-Zn-Mg-Cu alloys are widely used due to their excellent properties. For the 7056 aluminum alloy developed on the basis of 7055 aluminum alloy, exploring its aging characteristics and the effects of rare earth elements on its microstructure and mechanical properties has a great significance to promote the use of the alloy. In this paper, the as-cast alloy is subjected to homogenization treatment, extrusion, solution treatment, and aging treatment. The effect of adding 0.2% Sc to the 7056 aluminum alloy on the microstructure and properties of the alloy was investigated by analyzing the chemical composition of the alloy, observing the microstructure of the alloy in different states, observing the precipitated phase by transmission electron microscopy (TEM) and testing the hardness and tensile properties of the alloy after heat treatment. The experimental results show that the addition of Sc significantly refines the microstructure of the grains, and the as-cast grains decrease from 100-500 μm to about 50 μm. The addition of Sc element greatly improves the plasticity of the alloy. After the aging treatment, the elongation after fracture of the alloy increased from 10.82% to 13.60%, but the yield strength reduced from 668 MPa to 657 MPa. By comprehensively calculating the grain size and precipitation phase strengthening, the reasons for the decrease of the yield strength of the peak-aged 7056 aluminum alloy were analyzed in detail. Theoretical calculations show that when 0.2% of Sc is added to the alloy, after peak aging treatment, the strength of the alloy will decrease by 12.005 MPa, which is close to the test value of 11 MPa. Through the research, the best single-stage aging system condition for the 7056 aluminum alloy was found to be 120℃+16 h, and the corresponding peak hardness and strength were 195.2 HV and 714 MPa, respectively. At this time, the main strengthening phase of the alloy was a disk-shaped and short rod-shaped MgZn2 phase, which was about 4 to 6 nm in size, and the alloy also had a spherical Al3Zr phase with a size of about 20 nm.
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Key words:
- 7056 aluminum alloy /
- scandium /
- microstructure /
- mechanical property /
- aging
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圖 1 兩種合金在不同狀態下顯微組織. (a)7056鑄態合金; (b)7056+Sc鑄態合金; (c)7056鑄態合金; (d)7056+Sc鑄態合金; (e)7056固溶態合金; (f)7056+Sc固溶態合金; (g)7056時效態合金; (h)7056+Sc時效態合金
Figure 1. Microstructure of two alloys in different states: (a)7056 alloy (as-cast); (b)7056 alloy with Sc (as-cast); (c)7056 alloy (as-cast); (d)7056 alloy with Sc (as-cast); (e)7056 alloy (solid solution state); (f)7056 alloy with Sc (solid solution state); (g)7056 alloy (aging state); (h)7056 alloy with Sc (aging state)
圖 2 兩種合金在不同狀態下平均晶粒大小(1—鑄態; 2—固溶態; 3—時效態)
Figure 2. Average grain size of the two alloys in different states(1—as-cast; 2— solid solution; 3—aging)
圖 3 合金在T6態下透射電鏡圖及選區能譜分析. (a)不含Sc; (b)含Sc
Figure 3. TEM images for the alloy samples aged with T6 and EDS analysis results of the selected area: (a) without scandium; (b) with scandium
圖 4 不含Sc(a)和含Sc(b)的7056鋁合金的擠壓態顯微組織
Figure 4. Microstructures of the extrusion 7056 aluminum alloys without scandium (a) and with scandium (b)
圖 5 7056鋁合金在120 ℃時效過程中硬度變化曲線
Figure 5. Hardness curves of the 7056 aluminum alloys aged at 120 ℃
圖 6 T6態合金衍射花樣.(a)無Sc合金沿〈011〉晶帶軸衍射花樣; (b)含Sc合金沿〈001〉晶帶軸衍射花樣
Figure 6. Diffraction patterns of the alloy under T6 temperature: (a) diffraction pattern along the 〈011〉 crystal ribbon axis of the alloy without Sc; (b) diffraction pattern along the 〈001〉 crystal ribbon axis of the alloy with Sc
圖 7 兩種合金MgZn2相質量分數隨溫度變化圖
Figure 7. Graph of the percentage of MgZn2 phase in two alloys as a function of temperature
圖 8 7056鋁合金在不同時效溫度下的硬度曲線
Figure 8. Hardness curves of the 7056 aluminum alloys under various aging temperatures
圖 9 T6態7056鋁合金沉淀析出相. (a)晶界析出相; (b)晶內析出相
Figure 9. Precipitated phase of 7056 aluminum alloy under T6 state: (a) grain boundary precipitate; (b)intragranular precipitate
表 1 兩種合金的化學成分(質量分數)
Table 1. Chemical composition of the two alloys?
% 樣品 Zn Mg Cu Zr Si Fe Mn Ti Sc Al 1 9.56 1.94 1.46 0.18 0.0054 0.012 0.11 0.06 — 余量 2 9.44 1.93 1.50 0.18 0.0060 0.011 0.10 0.09 0.2 余量 
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久色视频表 2 兩種合金在固溶處理及時效處理后的機械性能
Table 2. Mechanical properties of the alloys under solution treatment and aging treatment
試樣 狀態 屈服強度/MPa 抗拉強度/MPa 斷后伸長率/% 1 固溶態 465 638 10.12 時效態 668 714 10.82 2 固溶態 418 588 11.28 時效態 657 693 13.60
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