(中南大學 材料科學與工程學院，長沙 410083)
摘 要: 采用光學顯微鏡、掃描電鏡、透射電鏡、常溫拉伸及斷裂韌性實驗，研究預拉伸對7050鋁合金板材力學性能和斷裂韌性的影響。結(jié)果表明：預拉伸引入大量位錯，時效過程中可以成為粗大平衡相η相的有利形核點；隨著預拉伸變形量的增大，η相的尺寸增加，板材的強度降低；晶界析出相間距增大，呈不連續(xù)分布，晶內(nèi)晶界之間的強度差減小，板材具有更高的變形抗力，斷裂韌性提高；預拉伸變形量增大導致晶界沉淀相粗化，無沉淀析出帶變寬，變形過程中容易產(chǎn)生應(yīng)力集中，對韌性不利；綜合組織結(jié)構(gòu)的正負面影響，隨著預拉伸變形量的增大，板材的斷裂韌性逐漸增大。
關(guān)鍵字: 7050鋁合金；預拉伸；拉伸性能；斷裂韌性
7050 aluminum alloy
（School of Materials Science and Engineering, Central South University, Changsha 410083, China）
Abstract:The effects of prestretching on the tensile property and fracture toughness of 7050 aluminum alloy plate were investigated by optical microscopy, scanning electron microscopy, transmission electron microscopy, tensile and toughness tests. The results show that many dislocations are generated in the prestretch process, and the dislocations can provide efficient nucleation sites for larger equilibrium phase η in the ageing. With increasing the prestretching, the size of the η phase increases, which results in the reduction in the strength. Furthermore, the distance between precipitates in the grain boundaries becomes larger. The precipitates discontinuously distribute in the grain boundaries. The strength-differential between the matrix and the boundary is reduced, which promotes more homogeneous deformation, and is beneficial to the fracture toughness. With increasing the prestretching, the precipitates in the grain boundary become coarser, and the precipitate free zones become wider, which assists the strain concentration in the deformation process and results in continuous decrease in the resistance to fracture. In a word, with increasing the prestretching, the fracture toughness increases.
Key words: 7050 aluminium alloy; prestretching; tensile property; fracture toughness
