【摘要】：本文以7085和7055合金為研究對象,采用TEM(透射電鏡)、OM(金相顯微鏡)、SEM(掃描電鏡)和EBSD(電子背散射衍射)系統(tǒng)研究了合金在典型時效及固溶工藝處理過程中析出相及晶粒組織的演變規(guī)律;以撕裂實驗測試UPE值(單位面積裂紋擴(kuò)展能)為主、緊湊拉伸試樣測試KIC值為輔,研究了合金經(jīng)典型時效及固溶工藝處理后的斷裂韌性變化規(guī)律;結(jié)合斷口形貌特征SEM分析,探討了時效析出相和晶粒組織特征與合金斷裂韌性的相關(guān)性。主要研究內(nèi)容及結(jié)果如下:撕裂實驗測定UPE值與緊湊拉伸試樣測定的KIC值在評價時效態(tài)7085和7055合金斷裂韌性的結(jié)果趨勢一致,可用于定性表征7xxx系鋁合金斷裂韌性的高低。合金經(jīng)不同制度的時效處理后,L-T向和T-L向撕裂實驗樣品的UPE值變化趨勢相同。研究了7085合金厚板經(jīng)單級時效與雙級時效后微觀組織與斷裂韌性的相關(guān)性。結(jié)果表明,合金在140℃單級時效過程中,晶內(nèi)主要的析出相為GP區(qū)和η′相。隨著時效時間的延長,晶內(nèi)析出相長大緩慢,晶界緩慢粗化,無沉淀析出帶(PFZ)逐漸加寬,合金沿晶斷裂比例增加,在達(dá)到足夠長的時間后有所下降,斷裂韌性隨時間變化呈先降低后升高趨勢。合金經(jīng)118℃/6h第一級預(yù)時效處理后,基體上析出細(xì)小的GP區(qū)和η′相,晶界析出相連續(xù);隨152℃第二級時效時間的延長,晶內(nèi)析出相不斷長大,η相數(shù)量呈增加趨勢,晶界析出相逐漸斷開,PFZ不斷加寬,合金沿晶斷裂比例先增加后減少,斷裂韌性隨時間變化呈先降低后升高趨勢。研究了7055合金厚板經(jīng)三級時效后微觀組織與斷裂韌性的相關(guān)性。隨著175℃第二級回歸時間的延長,晶界析出相不斷粗化,從連續(xù)到斷開,PFZ寬度不斷增加,合金的斷裂方式由沿晶斷裂向穿晶斷裂轉(zhuǎn)變,裂紋傳播方向逐漸不平行于軋向,韌窩數(shù)量增加,斷裂韌性逐漸升高。研究了7085合金經(jīng)固溶處理后晶粒組織與斷裂韌性的相關(guān)性。在本實驗范圍內(nèi),固溶溫度和固溶時間引起的晶粒組織結(jié)構(gòu)變化未對合金斷裂韌性產(chǎn)生顯著影響。
[Abstract]:In this paper, 7085 and 7055 alloys are studied. The evolution of precipitated phase and grain structure during typical aging and solution treatment were studied by TEM (Transmission Electron Microscopy), OM (metallographic microscope), SEM (scanning Electron microscope) and EBSD (Electron Backscatter diffraction) system. The fracture toughness of the alloy after aging and solution treatment was studied by using tear test UPE (crack growth energy per unit area) and compact tensile specimen (KIC). The fracture toughness was analyzed by SEM. The relationship between aging precipitation phase and grain structure and fracture toughness was discussed. The main research contents and results are as follows: the UPE value measured by tear test is consistent with the KIC value measured by compact tensile specimen in evaluating the fracture toughness of aged 7085 and 7055 alloys. It can be used to characterize the fracture toughness of 7xxx series aluminum alloy qualitatively. After aging treatment, the UPE values of L-T and T-L tearing samples were the same. The relationship between microstructure and fracture toughness of 7085 alloy thick plate after single stage aging and double stage aging was studied. The results show that the main precipitated phases in the alloy are GP region and 畏 'phase during single stage aging at 140 鈩，

本文編號：2267350