本文選題：7075鋁合金 + 欠時(shí)效��； 參考：《南昌航空大學(xué)》2017年碩士論文

【摘要】：7075鋁合金屬于可時(shí)效強(qiáng)化型Al-Zn-Mg-Cu系超高強(qiáng)度鋁合金,其優(yōu)異的室溫強(qiáng)度和良好的綜合性能,使其在航空,軍事,汽車,電子等領(lǐng)域得到了廣泛的應(yīng)用。本文利用熱處理爐、熱模擬試驗(yàn)機(jī)、SEM、EDS等設(shè)備,研究了固溶時(shí)間和單級(jí)時(shí)效對(duì)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(shí)效工藝。通過對(duì)欠時(shí)效態(tài)7075合金進(jìn)行熱模擬試驗(yàn),建立了7075鋁合金在欠時(shí)效狀態(tài)下的流變應(yīng)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(shí)間的延長(zhǎng),合金中的大部分第二相已經(jīng)溶于基體中,固溶時(shí)間為2h時(shí)固溶較完全,適宜的固溶工藝為470°C×2h。(2)隨著單級(jí)時(shí)效的時(shí)間延長(zhǎng)和溫度升高,在不同時(shí)效工藝下均存在強(qiáng)度峰值,當(dāng)時(shí)效的溫度高于120°C或時(shí)效時(shí)間大于24h時(shí),合金的抗拉強(qiáng)度和屈服強(qiáng)度均呈現(xiàn)不同程度的下降。當(dāng)時(shí)效制度為120°C×24h時(shí),合金的抗拉強(qiáng)度、屈服強(qiáng)度和硬度分別為:642.61MPa、549.2MPa和207HV,此時(shí)延伸率為10.36%。(3)對(duì)比105°C、120°C、135°C三種溫度的欠時(shí)效階段,120°C時(shí)效在同樣的時(shí)效時(shí)間時(shí),強(qiáng)度和塑性均優(yōu)于其他兩個(gè)溫度,其中120°C×16h的欠時(shí)效態(tài)7075鋁合金在抗拉強(qiáng)度大于620MPa時(shí),能夠保有11%以上的延伸率,作為后續(xù)熱變形試驗(yàn)的研究具有一定參考價(jià)值。(4)在120°C×16h欠時(shí)效態(tài)7075鋁合金的熱壓縮試驗(yàn)中,變形初期真應(yīng)力隨著真應(yīng)變的增加而迅速增加至峰值,在隨后的變形中真應(yīng)力會(huì)不斷下降至趨于穩(wěn)態(tài)。合金的熱變形過程中,真應(yīng)力隨應(yīng)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(yīng)變速率下,隨著溫度升高,不斷驅(qū)動(dòng)再結(jié)晶晶粒形核和長(zhǎng)大,在相同的的變形溫度下,較低的應(yīng)變速率,會(huì)使晶間滑移和位錯(cuò)的運(yùn)動(dòng)有更充分的時(shí)間進(jìn)行,故高的變形溫度和低的應(yīng)變速率有利于動(dòng)態(tài)再結(jié)晶的進(jìn)行。(5)合金的應(yīng)力因子α=0.0091MPa-1,變形激活能Q=230.805kJ/mol,應(yīng)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(yīng)力方程和用Z參數(shù)表示的材料流變應(yīng)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(yīng)變速率低溫區(qū)域和高應(yīng)變速率高溫區(qū)域,高應(yīng)變速率高溫區(qū)域的流變失穩(wěn)面積隨著真應(yīng)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(yīng)變速率0.01s-1~0.001s-1,采用多道次+小應(yīng)變量的加工方式進(jìn)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(xué)位授予單位】：南昌航空大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：TG146.21;TG166.3

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