淬火彈性應(yīng)變能對(duì)7050 鋁合金時(shí)效亞晶界演變的影響Effect of quenching elastic strain energy on evolution of sub-grain boundaries in 7050 Al alloy during aging

研究7050 鋁合金型材在固溶淬火與分級(jí)時(shí)效各階段亞晶界的演變，闡明亞晶界形成與晶粒內(nèi)取向梯度的關(guān)系。結(jié)果表明：固溶淬火后長(zhǎng)軸為200 μm、短軸為80 μm 的紡錘狀粗晶組織經(jīng)過(guò)(121 ℃，360 min)+(177 ℃，60 min)雙級(jí)時(shí)效處理后，被分割碎化成20 μm 左右的等軸狀細(xì)小亞晶組織。電子背散射衍射技術(shù)(EBSD)證實(shí)碎化由小角度晶界分割造成，且固溶淬火后晶面的彎曲程度經(jīng)時(shí)效后降低了77.8%。透射電鏡(TEM)結(jié)果表明，時(shí)效過(guò)程使淬火散亂位錯(cuò)逐步形成位錯(cuò)列和小角度晶界。二級(jí)時(shí)效時(shí)MgZn2 相在亞晶界上析出，促進(jìn)了Graff 試劑的侵蝕效果，使得在光學(xué)顯微鏡(OM)下可觀察到亞晶界。

The evolution of sub-grain boundaries of 7050 Al alloy profiles during solution quenching and interrupted aging treatment was studied,and the relationship between formation of the sub-grain boundaries and the orientation gradient was clarified. The results show that the spindle-shaped grains with 200 μm in length and 80 μm in width after solution quenching break into fine equiaxed sub-grains with average diameter of about 20 μm after duplex aging at (121℃,360 min) and (177 ℃,60 min). EBSD analysis demonstrates that grain refinement results from the segmentation of coarse grains by low angle grain boundaries and the lattice curvature due to solution quenching decreases by 77.8% after aging treatment. The investigation of TEM shows that the scattered dislocations by quenching arrange into dislocation arrays and low angle grain boundaries with aging time. MgZn2 precipitates on the sub-grain boundary,which helps the etchant Graff to visualize the sub-grain boundary using OM in the secondary aging.

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