7075鋁合金應(yīng)力時效強化與機制研究
發(fā)布時間：2018-07-26 11:43
【摘要】：Al-Zn-Mg-Cu系鋁合金屬于可熱處理強化型合金,廣泛應(yīng)用于航空航天和汽車結(jié)構(gòu)件。但傳統(tǒng)的T6等時效處理很難使得合金同時獲得高的強度和優(yōu)良的抗腐蝕性能。從熱力學的角度分析,應(yīng)力是與溫度和組分并列的第三個控制材料組織、結(jié)構(gòu)和性能變化的熱力學參量。開展彈性應(yīng)力下時效鋁合金組織與性能的系統(tǒng)研究,可以精確調(diào)控合金中的第二相組織,為高綜合性能鋁合金的制備提供新的實驗基礎(chǔ)和理論指導(dǎo)。本文采用掃描電鏡(SEM)、X射線衍射(XRD)和透射電鏡(TEM)分析技術(shù),結(jié)合力學性能測試,系統(tǒng)研究了外加應(yīng)力對7075合金時效組織與性能的影響。7075合金在160 oC應(yīng)力時效1 h后硬度呈現(xiàn)雙峰現(xiàn)象,在25 MPa、100 MPa拉應(yīng)力和25 MPa、112.5 MPa壓應(yīng)力處合金硬度達到最大值,其屈服強度和抗拉強度也明顯提高,延伸率略有下降。與無應(yīng)力時效狀態(tài)相比,四種應(yīng)力時效條件下時效析出相的彌散度更高,平均尺寸更小。拉、壓應(yīng)力促進了合金中較大尺寸MgZn2相的長大和η′亞穩(wěn)相的析出,壓應(yīng)力同時促進了η穩(wěn)定相的形成,而拉應(yīng)力則抑制了η相的析出。拉應(yīng)力使合金中晶界析出相呈現(xiàn)不連續(xù)分布狀態(tài)。研究了溫度對7075合金25 MPa應(yīng)力時效1 h的組織與性能的影響。在120-180oC經(jīng)壓應(yīng)力時效處理后合金的硬度、屈服強度和抗拉強度均高于同條件下的無應(yīng)力時效狀態(tài),且合金硬度在150oC時達到最高值178 HV;在較低溫度時(120oC)拉應(yīng)力時效使合金的硬度、屈服強度和抗拉強度低于同條件下的無應(yīng)力時效狀態(tài),在較高溫度時(160 oC)二者情況剛好相反,拉應(yīng)力時效的合金硬度在165 o C時達到最高值180 HV。合金在120oC應(yīng)力時效1 h后,25 MPa拉、壓應(yīng)力抑制了較大尺寸MgZn2相的長大;許多板狀GPII區(qū)在無應(yīng)力時效試樣中析出,大量似η′片狀體出現(xiàn)在拉應(yīng)力時效試樣中,許多η′亞穩(wěn)相被發(fā)現(xiàn)在壓應(yīng)力時效試樣中;各時效處理試樣中時效析出相的彌散度依次為:壓應(yīng)力時效狀態(tài)拉應(yīng)力時效狀態(tài)無應(yīng)力時效狀態(tài),析出相的平均尺寸分別為3.1 nm、6.3 nm和12.5 nm。研究了時效時間對7075合金在120 oC和160 oC經(jīng)25 MPa應(yīng)力時效的組織與性能的影響。與無應(yīng)力時效處理相比,120oC壓應(yīng)力時效處理1-32 h內(nèi)和160oC壓應(yīng)力時效處理1-10 h內(nèi)合金硬度、屈服強度和抗拉強度得到明顯提高。120 oC拉應(yīng)力時效8-24 h內(nèi)合金硬度升高較快,并在24 h時達到最高值191 HV,其屈服強度和抗拉強度則變化不大;160 oC拉應(yīng)力時效1-10 h內(nèi)合金硬度、屈服強度和抗拉強度得到明顯提高;在120oC經(jīng)25 MPa拉應(yīng)力時效處理24 h后,合金的抗晶間腐蝕和抗剝落腐蝕性能得到顯著增強。研究了7075合金的應(yīng)力時效機制。與無應(yīng)力時效狀態(tài)相比,25 MPa拉、壓應(yīng)力時效使合金中的蜷線位錯和位錯圈轉(zhuǎn)變?yōu)橹本�段位錯,應(yīng)力增加了時效析出相的形核率,析出相的彌散度增大,導(dǎo)致合金的機械性能升高;50 MPa拉應(yīng)力和75 MPa壓應(yīng)力時效使合金中的位錯發(fā)生滑移,位錯密度變低,并且位錯運動破壞了小尺寸的析出相晶核,使得析出相的彌散度降為最低,合金的機械性能變化不大;100 MPa拉應(yīng)力和112.5 MPa壓應(yīng)力時效使合金中的位錯滑移并產(chǎn)生大量增值,析出相的彌散度再次增大,合金的機械性能得到提高。相比于無應(yīng)力時效,25 MPa拉應(yīng)力時效降低了合金中較大尺寸MgZn2相的Zn/Mg值,而25 MPa壓應(yīng)力時效增大了MgZn2相中的Zn/Mg值。
[Abstract]:Al-Zn-Mg-Cu aluminum alloy is a heat-treated reinforced alloy, which is widely used in aerospace and automotive structural parts. However, the traditional T6 isoaging treatment is difficult to make the alloy obtain high strength and excellent corrosion resistance. From the thermodynamic point of view, the stress is the third control materials which are parallel to the temperature and components. The systematic study of the microstructure and properties of aging aluminum alloy under elastic stress can accurately regulate the secondary phase in the alloy and provide a new experimental basis and theoretical guidance for the preparation of high comprehensive properties of aluminum alloy. This paper uses scanning electron microscopy (SEM), X ray diffraction (XRD) and transmission electron microscopy (TEM). The effect of applied stress on the aging structure and properties of 7075 alloy 7075 alloy is studied systematically. The hardness of.7075 alloy in 160 oC stress aging is 1 h, and the hardness of the alloy reaches the maximum value at 25 MPa, 100 MPa tensile stress and 25 MPa, 112.5 MPa compressive stress, and its yield strength and tensile strength are also improved obviously. The elongation rate decreases slightly. Compared with the state without stress aging, the dispersion degree of the precipitated phase in the four stress aging conditions is higher and the average size is smaller. The tension stress promotes the growth of the larger size MgZn2 phase in the alloy and the precipitation of the ETA metastable phase, and the compressive stress also promotes the formation of the ETA stable phase, while the tensile stress inhibits the ETA phase. The tensile stress causes discontinuous distribution of the precipitates in the alloy MICROTEK boundary. The effect of temperature on the microstructure and properties of 7075 alloy 25 MPa stress aging is studied. The hardness, yield strength and tensile strength of the alloy after stress aging treatment in 120-180oC are higher than those under the same condition, and the hardness of the alloy is 150oC. At a relatively low temperature (120oC), the hardness, yield strength and tensile strength of the alloy are lower than the non stress aging state under the same condition at a lower temperature (120oC). At a higher temperature (160 oC) two, the hardness of the tensile stress aging alloy reaches the highest value of 180 HV. alloy at the 1 h of 120oC stress aging at 165 o C. After 25 MPa pulling, the compressive stress inhibits the growth of the larger size MgZn2 phase; many plate like GPII regions are precipitated in the non stress aging specimen, and a large number of eta 'flakes appear in the tensile stress aging specimen, and many of the ETA metastable phases are found in the pressure stress aging specimen; the dispersion degree of the aging precipitates in the physical specimens at each aging place is in turn the compressive stress. The aging state has no stress aging state. The average size of the precipitated phase is 3.1 nm, 6.3 nm and 12.5 nm., respectively, to study the effect of aging time on the microstructure and properties of 7075 alloy at 120 oC and 160 oC through 25 MPa stress aging. Compared with the non stress aging treatment, the 120oC pressure stress aging treatment is 1-32 h within and 160oC compressive stress. The hardness of the 1-10 h internal alloy, yield strength and tensile strength are obviously increased in.120 oC tensile stress aging 8-24 h, and the hardness of the alloy increases rapidly, and the maximum value is 191 HV at 24 h, and the yield strength and tensile strength change little; 160 oC tensile stress aging is 1-10 H internal gold hardness, yield strength and tensile strength are obviously raised. After 25 MPa tensile stress aging treatment with 25 MPa, the resistance to intercrystalline corrosion and exfoliation corrosion of the alloy was significantly enhanced. The stress aging mechanism of 7075 alloy was studied. Compared with the state of non stress aging, 25 MPa pull and pressure stress aging made the curled line dislocation and dislocation in the alloy into a straight line dislocation, and the stress increased the aging time. The nucleation rate of the precipitated phase and the dispersion degree of the precipitated phase increase and the mechanical properties of the alloy increase. 50 MPa tensile stress and 75 MPa pressure stress aging make the dislocation slip and the dislocation density lower, and the dislocation motion destroys the small size of the precipitated phase nucleation, which makes the dispersion degree of the precipitated phase to be the lowest, and the mechanical properties of the alloy changes. 100 MPa tensile stress and 112.5 MPa stress stress aging make the dislocation slip and increase a lot of increment in the alloy, the dispersion degree of the precipitated phase increases again, and the mechanical properties of the alloy are improved. Compared to the non stress aging, the 25 MPa tensile stress aging reduces the Zn/Mg value of the larger size MgZn2 phase in the alloy, and the 25 MPa pressure stress aging increases MgZ. The Zn/Mg value in the N2 phase.
【學位授予單位】：燕山大學
【學位級別】：博士
【學位授予年份】：2015
【分類號】：TG146.21
本文編號：2145899
[Abstract]:Al-Zn-Mg-Cu aluminum alloy is a heat-treated reinforced alloy, which is widely used in aerospace and automotive structural parts. However, the traditional T6 isoaging treatment is difficult to make the alloy obtain high strength and excellent corrosion resistance. From the thermodynamic point of view, the stress is the third control materials which are parallel to the temperature and components. The systematic study of the microstructure and properties of aging aluminum alloy under elastic stress can accurately regulate the secondary phase in the alloy and provide a new experimental basis and theoretical guidance for the preparation of high comprehensive properties of aluminum alloy. This paper uses scanning electron microscopy (SEM), X ray diffraction (XRD) and transmission electron microscopy (TEM). The effect of applied stress on the aging structure and properties of 7075 alloy 7075 alloy is studied systematically. The hardness of.7075 alloy in 160 oC stress aging is 1 h, and the hardness of the alloy reaches the maximum value at 25 MPa, 100 MPa tensile stress and 25 MPa, 112.5 MPa compressive stress, and its yield strength and tensile strength are also improved obviously. The elongation rate decreases slightly. Compared with the state without stress aging, the dispersion degree of the precipitated phase in the four stress aging conditions is higher and the average size is smaller. The tension stress promotes the growth of the larger size MgZn2 phase in the alloy and the precipitation of the ETA metastable phase, and the compressive stress also promotes the formation of the ETA stable phase, while the tensile stress inhibits the ETA phase. The tensile stress causes discontinuous distribution of the precipitates in the alloy MICROTEK boundary. The effect of temperature on the microstructure and properties of 7075 alloy 25 MPa stress aging is studied. The hardness, yield strength and tensile strength of the alloy after stress aging treatment in 120-180oC are higher than those under the same condition, and the hardness of the alloy is 150oC. At a relatively low temperature (120oC), the hardness, yield strength and tensile strength of the alloy are lower than the non stress aging state under the same condition at a lower temperature (120oC). At a higher temperature (160 oC) two, the hardness of the tensile stress aging alloy reaches the highest value of 180 HV. alloy at the 1 h of 120oC stress aging at 165 o C. After 25 MPa pulling, the compressive stress inhibits the growth of the larger size MgZn2 phase; many plate like GPII regions are precipitated in the non stress aging specimen, and a large number of eta 'flakes appear in the tensile stress aging specimen, and many of the ETA metastable phases are found in the pressure stress aging specimen; the dispersion degree of the aging precipitates in the physical specimens at each aging place is in turn the compressive stress. The aging state has no stress aging state. The average size of the precipitated phase is 3.1 nm, 6.3 nm and 12.5 nm., respectively, to study the effect of aging time on the microstructure and properties of 7075 alloy at 120 oC and 160 oC through 25 MPa stress aging. Compared with the non stress aging treatment, the 120oC pressure stress aging treatment is 1-32 h within and 160oC compressive stress. The hardness of the 1-10 h internal alloy, yield strength and tensile strength are obviously increased in.120 oC tensile stress aging 8-24 h, and the hardness of the alloy increases rapidly, and the maximum value is 191 HV at 24 h, and the yield strength and tensile strength change little; 160 oC tensile stress aging is 1-10 H internal gold hardness, yield strength and tensile strength are obviously raised. After 25 MPa tensile stress aging treatment with 25 MPa, the resistance to intercrystalline corrosion and exfoliation corrosion of the alloy was significantly enhanced. The stress aging mechanism of 7075 alloy was studied. Compared with the state of non stress aging, 25 MPa pull and pressure stress aging made the curled line dislocation and dislocation in the alloy into a straight line dislocation, and the stress increased the aging time. The nucleation rate of the precipitated phase and the dispersion degree of the precipitated phase increase and the mechanical properties of the alloy increase. 50 MPa tensile stress and 75 MPa pressure stress aging make the dislocation slip and the dislocation density lower, and the dislocation motion destroys the small size of the precipitated phase nucleation, which makes the dispersion degree of the precipitated phase to be the lowest, and the mechanical properties of the alloy changes. 100 MPa tensile stress and 112.5 MPa stress stress aging make the dislocation slip and increase a lot of increment in the alloy, the dispersion degree of the precipitated phase increases again, and the mechanical properties of the alloy are improved. Compared to the non stress aging, the 25 MPa tensile stress aging reduces the Zn/Mg value of the larger size MgZn2 phase in the alloy, and the 25 MPa pressure stress aging increases MgZ. The Zn/Mg value in the N2 phase.
【學位授予單位】：燕山大學
【學位級別】：博士
【學位授予年份】：2015
【分類號】：TG146.21
【相似文獻】
相關(guān)期刊論文 前10條
1 湛利華;賈樹峰;張姣;;電脈沖時效對7075鋁合金組織和性能的影響[J];中國有色金屬學報;2014年03期
2 陳健;梁歡;劉雪飄;;CuNiCoBe合金冷變形時效特性[J];材料熱處理學報;2010年10期
3 王宏偉;易丹青;蔡金伶;王斌;;應(yīng)力時效對2E12鋁合金的力學性能和微觀組織的影響[J];中國有色金屬學報;2011年12期
4 陳綺倫;鈹青銅彈性零件時效的晶界晶內(nèi)特征及組織性能的實驗研究[J];宇航材料工藝;1989年06期
5 朱耀明;夏海軍;曹顯良;;儀表用Al-Cu-Zn-Mg合金的雙級時效[J];輕合金加工技術(shù);1989年04期
6 陳志國,鄭子樵,李競舟;Al0-1.12Mg-0.66Si-0.8Cu合金熱處理及微觀組織研究[J];礦冶工程;2001年04期
7 李潤霞,李榮德,楊秀英,李晨曦,胡壯麒;高強度鑄造Al-Si-Cu-Mg合金時效特性的研究[J];鑄造;2003年06期
8 高俊生;;軟態(tài)分級時效對鈹青銅(QBe2)斷口和硬度的影響[J];昆明工學院學報;1987年04期
9 孫乃箴;劉和法;戴學禮;武清泉;;CuCo2Be高強、高導(dǎo)合金固溶與脫溶的研究[J];金屬熱處理學報;1988年01期
10 高俊生;;鈹青銅(QBe2)軟態(tài)分級時效的斷口分析[J];金屬熱處理;1988年02期
相關(guān)博士學位論文 前4條
1 郭偉;7075鋁合金應(yīng)力時效強化與機制研究[D];燕山大學;2015年
2 李吉慶;含銅超輕鎂鋰合金制備及其時效析出行為研究[D];哈爾濱工程大學;2011年
3 齊福剛;Sn和Ce對Mg-Zn-Mn高強變形鎂合金組織和性能的影響[D];重慶大學;2012年
4 胡少虬;大直徑高強度高塑性高彈性模量鋁合金研制及淬火殘余應(yīng)力演變規(guī)律研究[D];中南大學;2007年
相關(guān)碩士學位論文 前10條
1 高青;抗菌Al-Mg-Si合金組織與性能研究[D];山東建筑大學;2015年
2 蔣云澤;回歸再時效制度對噴射成形7055鋁合金組織和性能的影響[D];江蘇科技大學;2015年
3 鄭進城;鋁硅鎂合金時效理論及實驗表征[D];廣西大學;2008年
4 李智燕;電場時效對2E12鋁合金的組織和性能的影響[D];中南大學;2009年
5 何國強;鋁硅鎂合金時效雙峰現(xiàn)象與鋁銅合金時效電化學表征[D];廣西大學;2008年
6 周亮;形變熱處理對2124鋁合金蠕變時效的影響[D];中南大學;2011年
7 洪天然;電場時效對2E12鋁合金和Al-4Cu合金微觀組織的影響和機理[D];中南大學;2012年
8 魯曉超;2A97鋁合金蠕變時效成形研究[D];中南大學;2014年
9 馮晶;CuCr合金時效析出的第一原理計算與分子動力學模擬[D];昆明理工大學;2009年
10 賈樹峰;2219鋁合金電脈沖作用下的應(yīng)力時效行為研究[D];中南大學;2014年
，本文編號：2145899
本文鏈接：http://sikaile.net/kejilunwen/jinshugongy/2145899.html
最近更新
教材專著
