Microstructural Evolution of 7050 Aluminum Alloy Semisolid Billets Fabricated by RAP Process
Microstructural Evolution of 7050 Aluminum Alloy Semisolid Billets Fabricated by RAP Process
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DOI：
10.4028/www.scientific.net/ssp.217-218.29
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发表时间：
2014-09
期刊：
影响因子：
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通讯作者：
Jufu Jiang;Z. Du;Ying Wang;Shou-jing Luo
中科院分区：
文献类型：
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作者：
Jufu Jiang;Z. Du;Ying Wang;Shou-jing Luo
在本研究中，7050在挤压状态下提供加热到不同的温度低于固相线或半固态和显微组织的演变和粗化进行了研究。结果表明，在545°C保温5 min后，合金才发生完全再结晶，形成大量细小的等轴晶。RAP适用于制备平均晶粒尺寸为47.4 ~ 70.5 μ m、圆度为1.3 ~ 1.7的高质量7050铝合金半固态坯料。当样品在610°C和615° C下浸泡较长时间时，会发生晶粒生长。当等温温度为610°C和615°C时，粗化速率常数分别为359.5μ m3 s-1和470.5μ m3 s-1，表明粗化速率常数（K）随着等温温度的升高而增大。粗化倾向于通过奥斯特瓦尔德熟化和聚结发生。在整个粗化过程中，Ostwald熟化起着重要作用，但晶粒聚结仅在浸泡12 min后才对粗化有贡献。625°C是保持样品圆柱形的最佳温度，因为高于该温度样品会塌陷，导致难以夹持。
In the present study, 7050 supplied in extruded state was heated to different temperatures below solidus or the semisolid state and microstructural evolution and coarsening were investigated. The results showed that complete recrystallisation only occurs after soaking for 5 minutes at 545°C, which is characterised by formation of a lot of fine equiaxed grains. RAP is suitable for fabricating high-quality semisolid billet of 7050 aluminum alloy with an average grain size ranging from 47.4 um to 70.5 um and a roundness ranging from 1.3 to 1.7. Grain growth occurs as the samples were soaked at 610°C and 615°Cfor prolonged soaking time. When the isothermal temperatures were 610°C and 615°C, the coarsening rate constants were 359.5μm3s-1 and 470.5μm3s-1, respectively, indicating an increase of coarsening rate constant (K) with the increasing isothermal temperature. Coarsening tends to occur via Ostwald ripening and coalescence. Ostwald ripening plays an important role during the whole coarsening process, but the grain coalescence only contributes to coarsening after soaking for 12 minutes. 625°C is an optimal temperature to keep cylinder shape of the sample due to collapse of the sample above this temperature, leading to difficult clamping.