雙級淬火對車身板用6016鋁合金烤漆硬化效應(yīng)的影響Influence of interrupted quenching on paint-bake response of AA6016 Al alloy sheet

以硬度為主要表征手段研究雙級淬火的中間淬火溫度和保溫時(shí)間對6016鋁合金板材的時(shí)效及模擬烤漆行為的影響。采用DSC和透射電鏡對比分析常規(guī)淬火和雙級淬火對隨后自然時(shí)效態(tài)樣品與烤漆態(tài)樣品納米相的影響。結(jié)果表明：最佳的中間淬火工藝制度為(100 ℃, 1 h)，并且該工藝下合金自然時(shí)效過程性能穩(wěn)定，但隨后人工時(shí)效硬化速率大；雙級淬火樣品自然時(shí)效后表現(xiàn)出良好的塑性(δ＞28%)、成形性(σ_0.2＜120 MPa，n≈0.24，r≈0.78)和模擬烤漆后強(qiáng)化能力(σ_0.2＞220 MPa，PBR＞110 MPa)。雙級淬火樣品在100 ℃淬火時(shí)形成了均勻彌散并大于臨界尺寸的Mg-Si團(tuán)簇。這些團(tuán)簇可抑制自然時(shí)效過程中小尺寸團(tuán)簇的形成，從而保持這些樣品的性能基本不變。這些團(tuán)簇使得隨后人工時(shí)效過程中β″相激活能由76.0 kJ/mol降至57.5kJ/mol，促進(jìn)了模擬烤漆后形成的β″相的析出，從而提高雙級淬火樣品的烤漆硬化效果。

The influence of interrupted quenching temperature and holding time on the aging hardening behavior and paint-bake response of the AA6016 aluminum alloy was investigated with hardness test. The nano-size precipitates in the natural aged and paint-baked samples pre-processed by normal quenching or interrupted quenching were analyzed by DSC and TEM. The results show that the optimized interrupted quenching treatment is (100 ℃, 1 h). For the sample processed with this interrupted quenching, the hardness remains almost unchanged during natural aging, but the following artificial aging shows high hardening rate. The tensile test results also reveal that the interrupted quenching sample shows good ductility (δ＞28%), formability (σ_0.2＜120MPa, n≈0.24, r≈0.78) and paint bake hardening response (σ_0.2＞220 MPa，PBR＞110 MPa). The samples after interrupted quenching at 100 ℃ form many Mg-Si clusters that distribute homogeneously and have the size larger than critical size. These clusters suppress the formation of small clusters during natural aging, therefore, the properties of the samples remain almost unchanged. These clusters decrease the precipitation activation energy of β″ precipitates from 76.0 kJ/mol to 57.5 kJ/mol, which accelerates the precipitation of β″ precipitates, and increase the paint-bake hardening response of interrupted quenching samples.

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