連續(xù)冷卻對Al-4%Cu合金時效組織和性能的影響

連續(xù)冷卻對Al-4%Cu合金時效組織和性能的影響Effect of continuous cooling on aging microstructures and properties of Al-4%Cu alloy

采用掃描電鏡、透射電鏡觀察、選區(qū)電子衍射、電阻率測試、硬度測試和Monte Carlo模擬等方法，研究連續(xù)冷卻對Al-4%Cu合金(質(zhì)量分?jǐn)?shù))時效組織和性能的影響。結(jié)果表明，實驗合金的連續(xù)冷卻脫溶產(chǎn)物主要包括θ相、θ′相和θ″相，不同冷卻條件形成的析出相組態(tài)會導(dǎo)致合金的硬度曲線、電阻率曲線不隨冷卻速率的降低而單調(diào)降低。冷卻析出的θ″相作為時效強化相的前驅(qū)體能夠加速時效強化相析出，導(dǎo)致合金的時效硬化曲線峰值時間提前，但是極慢的冷卻條件消耗了大量的溶質(zhì)原子，導(dǎo)致時效驅(qū)動力下降。Monte Carlo模擬表明，連續(xù)冷卻脫溶導(dǎo)致的殘余溶質(zhì)質(zhì)量分?jǐn)?shù)降低會減慢Cu原子團簇的形成速率，當(dāng)殘余溶質(zhì)質(zhì)量分?jǐn)?shù)低于2%時，模擬時效1800s合金中仍然不會出現(xiàn)明顯的團簇，降低了時效強化效率。

The effect of continuous cooling process on aging microstructure and properties was investigated by means of scanning electron microscopy (SEM), transmission electron microscopy (TEM), selected area electron diffraction (SAED), electrical resistivity, hardness test and Monte Carlo simulation. The result show that the cooling precipitations are θ, θ′ and θ″ phases. The hardness and electrical resistivity are not monotone decrease with the extending of cooling ending time, since the different microstructures induced by different cooling processes. θ″ phase precipitated in cooling processes is acted as precursor of θ′ phase, as a result, an earlier peak hardness value is observed. However, extremely slow cooling processes will lead to the significant consumption of alloy atoms, in which the driving force for aging precipitation decreases. The results of Monte Carlo simulation reveal that the decrease of residual solid solution will delay the formation of Cu rich clusters in the early stage of aging. If the residual solid solution is less than 2%, few clusters are observed after simulating aging for 1800s and which decreases the efficiency of aging hardening.

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