【摘要】：7003鋁合金屬于A1-Zn-Mg系高強鋁合金,具有良好的熱變形能力和加工性能,具有優(yōu)良的可焊性,焊接后可以自動時效,有良好的疲勞強度。近年來,7003鋁合金的應(yīng)用越來越廣泛,其被廣泛應(yīng)用于航空航天、汽車工業(yè)領(lǐng)域。提高7003鋁合金的性能可以使其更好地應(yīng)用于各領(lǐng)域。 SPD(大塑形變形)技術(shù)是晶粒細化以提高材料強度的一種有效方法。研究表明在SPD過程中,當(dāng)晶粒細化到1μm后,材料將表現(xiàn)出一系列不尋常的物理、化學(xué)和力學(xué)性能。因此,研究鋁合金的晶粒細化方法具有重要的理論意義和應(yīng)用意義。SPD制備超細晶材料的工藝方法眾多,作為細化晶粒的方法之一,等徑角擠壓技術(shù)(ECAP)能夠強烈的細化晶粒,且工藝簡單、生產(chǎn)成本低、制得的超細晶材料以其優(yōu)良的性能受到材料科學(xué)界的廣泛關(guān)注,具有良好的應(yīng)用價值和前景。 論文對7003鋁合金進行五道次ECAP(等徑角擠壓),對擠壓后的材料通過金相顯微鏡、透射電子顯微鏡及X射線衍射技術(shù)進行顯微組織觀察,結(jié)果表明：隨著等通道擠壓法道次的增加,7003鋁合金試樣晶粒發(fā)生了明顯細化,在ECAP過程中,晶界逐漸沿剪切變形方向發(fā)生平直化轉(zhuǎn)變。隨著擠壓道次的增加,材料內(nèi)部位錯密度升高,位錯纏結(jié)加劇,五道次等通道擠壓后,位錯密度不再增加反而減少,位錯纏結(jié)逐漸轉(zhuǎn)變成細小的亞晶粒,平均晶粒尺寸為400nm左右,實現(xiàn)晶粒細化。 對擠壓后試樣進行了拉伸、壓縮實驗并進行硬度測試,結(jié)果表明：隨著等通道擠壓道次增加,材料力學(xué)性能明顯改善。研究顯示：從一道次到四道次,抗拉強度由336.17MPa增加到405.33MPa,增加了20.5%；壓縮屈服強度由265MPa增加到421MPa,增加了58.9%；試樣X面的顯微硬度由72.8HV增加到138.4HV,增加了90%。 對擠壓后試樣進行再結(jié)晶退火處理,對比分析不同再結(jié)晶退火制度對組織演變的影響,獲得試樣最佳組織控制工藝為：ECAP四道次,退火溫度160℃,保溫時間為1h,此時獲得的試樣晶粒的平均尺寸不會增大,而且有進一步細化的趨勢。該研究結(jié)果可為進一步深入研究或采用ECAP法生產(chǎn)高強鋁合金提供參考。
[Abstract]:7003 aluminum alloy belongs to A1-Zn-Mg high strength aluminum alloy, it has good thermal deformation ability and processing property, excellent weldability, automatic aging after welding, and good fatigue strength. In recent years, 7003 aluminum alloy has been widely used in aerospace and automobile industry. Improving the properties of 7003 aluminum alloy can make it better used in various fields of. SPD (plastic deformation) technology is an effective method of grain refinement to improve the strength of the material. The results show that during the SPD process, when the grain is refined to 1 渭 m, the material will exhibit a series of unusual physical, chemical and mechanical properties. Therefore, it is of great theoretical and practical significance to study the grain refinement method of aluminum alloy. As one of the methods of grain refinement, (ECAP) can refine the grain strongly, as one of the methods of preparing ultrafine grain material by SPD. The ultrafine grained materials with simple process, low production cost and excellent properties have attracted wide attention of the material science community, and have good application value and prospect. In this paper, 7003 aluminum alloy was extruded by ECAP (Equal Channel angular Extrusion) for five times. The microstructure of the extruded aluminum alloy was observed by metallographic microscope, transmission electron microscope and X-ray diffraction technique. The results show that the grain size of 7003 aluminum alloy samples is obviously refined with the increase of the pass number of equal channel extrusion, and the grain boundary changes gradually along the direction of shear deformation during ECAP. With the increase of extrusion pass, the dislocation density inside the material increases, the dislocation entanglement intensifies, the dislocation density decreases instead of increasing, and the dislocation entanglement gradually changes into fine sub-grains. The average grain size is about 400nm to realize grain refinement. The tensile, compression and hardness tests of the extruded samples were carried out. The results showed that the mechanical properties of the samples improved obviously with the increase of the number of extrusion passes. The results show that from one to four passes, the tensile strength increases from 336.17MPa to 405.33 MPa, the compressive yield strength increases from 265MPa to 421 MPa and increases 58.9%, and the microhardness of the X plane increases from 72.8HV to 138.4 HVV, which increases 90%. The effect of different recrystallization annealing systems on the microstructure evolution of the extruded samples was compared and analyzed. The results showed that the optimum microstructure control process was as follows: ECAP four times, annealing temperature 160 鈩，

本文編號：2277697