本文選題：7075鋁合金 + 欠時效�。� 參考：《南昌航空大學》2017年碩士論文

【摘要】：7075鋁合金屬于可時效強化型Al-Zn-Mg-Cu系超高強度鋁合金,其優(yōu)異的室溫強度和良好的綜合性能,使其在航空,軍事,汽車,電子等領域得到了廣泛的應用。本文利用熱處理爐、熱模擬試驗機、SEM、EDS等設備,研究了固溶時間和單級時效對7075鋁合金組織及性能的影響,確定了適合用來熱變形的欠時效工藝。通過對欠時效態(tài)7075合金進行熱模擬試驗,建立了7075鋁合金在欠時效狀態(tài)下的流變應力本構(gòu)方程和熱加工圖,并分析了變形組織,結(jié)果表明:(1)在470°C下隨固溶時間的延長,合金中的大部分第二相已經(jīng)溶于基體中,固溶時間為2h時固溶較完全,適宜的固溶工藝為470°C×2h。(2)隨著單級時效的時間延長和溫度升高,在不同時效工藝下均存在強度峰值,當時效的溫度高于120°C或時效時間大于24h時,合金的抗拉強度和屈服強度均呈現(xiàn)不同程度的下降。當時效制度為120°C×24h時,合金的抗拉強度、屈服強度和硬度分別為:642.61MPa、549.2MPa和207HV,此時延伸率為10.36%。(3)對比105°C、120°C、135°C三種溫度的欠時效階段,120°C時效在同樣的時效時間時,強度和塑性均優(yōu)于其他兩個溫度,其中120°C×16h的欠時效態(tài)7075鋁合金在抗拉強度大于620MPa時,能夠保有11%以上的延伸率,作為后續(xù)熱變形試驗的研究具有一定參考價值。(4)在120°C×16h欠時效態(tài)7075鋁合金的熱壓縮試驗中,變形初期真應力隨著真應變的增加而迅速增加至峰值,在隨后的變形中真應力會不斷下降至趨于穩(wěn)態(tài)。合金的熱變形過程中,真應力隨應變速率的提高而變大,隨變形溫度的升高而變小。在相同的應變速率下,隨著溫度升高,不斷驅(qū)動再結(jié)晶晶粒形核和長大,在相同的的變形溫度下,較低的應變速率,會使晶間滑移和位錯的運動有更充分的時間進行,故高的變形溫度和低的應變速率有利于動態(tài)再結(jié)晶的進行。(5)合金的應力因子α=0.0091MPa-1,變形激活能Q=230.805kJ/mol,應力指數(shù)n=5.926,結(jié)構(gòu)因子A=4.84×1017s-1,將這些材料參數(shù)帶入可得到用Arrhenius雙曲正弦函數(shù)表示的流變應力方程和用Z參數(shù)表示的材料流變應力本構(gòu)方程。(6)合金的熱變形流變失穩(wěn)區(qū)主要集中在高應變速率低溫區(qū)域和高應變速率高溫區(qū)域,高應變速率高溫區(qū)域的流變失穩(wěn)面積隨著真應變的增大而變大,失穩(wěn)區(qū)組織不均勻且存在變形缺陷。該合金的適宜變形條件為:變形溫度400°C~450°C,應變速率0.01s-1~0.001s-1,采用多道次+小應變量的加工方式進行變形。
[Abstract]:The 7075 aluminum alloy belongs to the aging strengthened Al-Zn-Mg-Cu system ultra high strength aluminum alloy, its excellent room temperature strength and good comprehensive performance, make it in aviation, military, automobile, electronics and other fields have been widely used. In this paper, the effects of solution time and single stage aging on the microstructure and properties of 7075 aluminum alloy have been studied by means of heat treatment furnace and thermal simulation test machine, etc. The underaging process suitable for thermal deformation has been determined. Based on the thermal simulation test of underaged 7075 alloy, the constitutive equation of rheological stress and hot working diagram of 7075 aluminum alloy under underaging state are established. The deformation microstructure is analyzed. The results show that the solution time of 7075 aluminum alloy increases with the increase of solution time at 470 擄C. Most of the second phases in the alloy have been dissolved in the matrix, and the solution is more complete when the solution time is 2 h. The suitable solution process is 470 擄C 脳 2h.f.) with the increase of the single stage aging time and the increase of temperature, there is a peak value of strength in different aging processes. When the aging temperature is higher than 120 擄C or the aging time is longer than 24 h, the tensile strength and yield strength of the alloy decrease in varying degrees. When the aging system is 120 擄C 脳 24 h, the tensile strength, yield strength and hardness of the alloy are: 642.61 MPA and 207HVrespectively, and the elongation is 10.36%. The tensile strength and plasticity of the underaged 7075 aluminum alloy at 120 擄C 脳 16 h are superior to those of the other two temperatures. When the tensile strength is greater than 620MPa, the elongation of 7075 aluminum alloy can retain more than 11%. The study as a follow-up hot deformation test has certain reference value.) in the thermal compression test of 7075 aluminum alloy with underaging state of 120 擄C 脳 16 h, the initial true stress of deformation increases rapidly to the peak with the increase of true strain. During subsequent deformation, the true stress will decrease to steady state. During hot deformation, the true stress increases with the increase of strain rate and decreases with the increase of deformation temperature. At the same strain rate, the recrystallization grain nucleation and growth are driven continuously with the increase of temperature. At the same deformation temperature, the lower strain rate will make the movement of intergranular slip and dislocation more sufficient time. Therefore, high deformation temperature and low strain rate are favorable to dynamic recrystallization. The stress factor 偽 (0.0091MPa-1), the deformation activation energy (Q) 230.805kJ / mol, the stress exponent nr 5.926, and the structural factor A4.84 脳 1017s-1 are favorable for dynamic recrystallization. The Arrhenius hyperbolic sinusoidal function can be obtained by using these parameters. The flow stress equation and the constitutive equation of material rheological stress expressed by Z parameter are mainly concentrated in the high strain rate low temperature region and the high strain rate high temperature region in the hot deformation rheological instability region of the alloy. The rheological instability area in the high strain rate region increases with the increase of true strain, and the microstructure is not uniform and there are deformation defects in the instability zone. The suitable deformation conditions of the alloy are as follows: the deformation temperature is 400 擄C, and the strain rate is 0.01s-1n 0.001s-1.The deformation is carried out by means of multi-pass small strain.
【學位授予單位】：南昌航空大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TG146.21;TG166.3

【參考文獻】

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1 劉海軍;;含稀土AZ31鎂合金熱壓縮變形行為及加工圖[J];特種鑄造及有色合金;2017年01期

2 趙亞楠;江樹勇;張艷秋;朱曉明;;NiTi形狀記憶合金的熱變形行為及熱加工圖[J];應用科技;2017年01期

3 張永強;郭鴻鎮(zhèn);雷文光;韓棟;毛小南;;TC18鈦合金熱加工圖構(gòu)建、分析及有效性驗證[J];鈦工業(yè)進展;2015年02期

4 郭俊鋒;周旭東;李漢;;鑄態(tài)27SiMn鋼熱變形行為及熱加工圖[J];材料熱處理學報;2014年12期

5 黃順U，

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