天堂国产午夜亚洲专区-少妇人妻综合久久蜜臀-国产成人户外露出视频在线-国产91传媒一区二区三区

當前位置:主頁 > 科技論文 > 鑄造論文 >

AZ31鎂合金寬應變率下各向異性力學行為及形變機制研究

發(fā)布時間:2018-10-23 18:05
【摘要】:鎂合金作為一種輕質(zhì)結(jié)構材料,在汽車和航空等領域的應用前景廣闊。然而,室溫環(huán)境中較強的各向異性限制了鎂合金的廣泛應用。為克服這一缺點,許多學者開展了大量宏觀力學行為和微觀結(jié)構演化方面的研究,但微觀結(jié)構演化如何影響鎂合金的宏觀力學行為仍不清楚,缺乏聯(lián)系宏觀與微觀變形的細觀尺度的測量。有關鎂合金各向異性變形的原因眾說紛紜,尚未達成共識。本文利用原位實時同步輻射X射線相襯成像和衍射多尺度測量方法研究不同應變率加載下鎂合金的各向異性變形。實驗設計兩種加載方式,加載方向垂直或平行于變形鎂合金的c軸,分別記為LA⊥c和LA‖c。在鎂合金變形過程中,實現(xiàn)宏觀應力—應變曲線、細觀應變場和微觀衍射圖譜的同時采集。電子背散射衍射技術用于回收樣品中的變形孿晶的表征。1、室溫環(huán)境中準靜態(tài)壓縮加載,應變率5XI0-4 s-1,LA⊥c和LA‖c樣品的應力—應變曲線、應變場和衍射圖譜演化均呈現(xiàn)明顯的差異。對于LA⊥c樣品,{1012}拉伸孿生主導塑性變形,應力梯度通過孿生被迅速釋放并使應變場變得均勻化,應變局域化程度的降低有效激發(fā)了應變硬化率的增加。然而LA‖c樣品中的塑性變形主要依賴位錯運動,位錯在缺陷處形核并纏結(jié)引起應變集中,細觀非均勻變形導致應變硬化率的降低。2、高溫環(huán)境中準靜態(tài)壓縮加載,應變率10-3 s-1,鎂合金的宏觀力學性能、細觀應變場和微觀晶格變形呈現(xiàn)明顯的各向異性。由于初始織構的差異,在室溫和高溫下,{1012}拉伸孿晶主導LA⊥c樣品的塑性變形,而位錯運動則在LA‖c樣品中較為盛行。隨著溫度的升高,LA⊥c樣品中激發(fā)的{1012}拉伸孿晶的數(shù)量逐漸減少,使得應變場的均勻化程度降低;高溫下,LA‖c樣品中{1122}c + a錐面滑移較易啟動,使得LA‖c樣品在高溫下呈現(xiàn)更加均勻的變形。{1012}拉伸孿晶和錐面c + aa滑移均能通過協(xié)調(diào)垂直和平行于加載方向的變形使塑性變形變得均勻化。應變場不均勻度的差異導致LA⊥c和LA‖c樣品的應變硬化率呈現(xiàn)明顯的差異。3、分離式霍普金森壓桿加載,應變率約為5.5×103 s-1,鎂合金的動態(tài)響應同準靜態(tài)加載類似呈現(xiàn)較強的各向異性。{1012}拉伸孿晶使得應變場的不均勻度減小,應變場局域化程度的減小有效激發(fā)了應變硬化率的增加;位錯運動引起非均勻變形,應變場不均勻度的升高導致應變硬化率的減小。然而,在塑性變形的初期,動態(tài)加載過程中孿生主導塑性變形,而準靜態(tài)加載下主導塑性變形的則是位錯運動,表明加載應變率在一定程度上影響著鎂合金的變形模式。4、平板撞擊加載,應變率0.92~1.35×105s-1 LA⊥c和LA‖c樣品的彈塑性轉(zhuǎn)變呈現(xiàn)明顯的各向異性,但二者的雨貢紐彈性極限基本相同,約為0.32 GPa。低速撞擊下LA⊥c樣品的層裂強度略高于LA‖c樣品,隨著撞擊速度的增加,二者的層裂強度均隨撞擊速度的增加而增加,且差異減小;當撞擊速度增加至400 m/s時,LA⊥c和LA‖c樣品的層裂強度基本一致。LA⊥c樣品中形成大量的{1012}拉伸孿晶,LA‖c樣品中孿晶數(shù)量較少。
[Abstract]:As a lightweight structural material, magnesium alloy has a wide application prospect in automobile and aviation. However, the strong anisotropy in the room temperature environment limits the wide application of magnesium alloys. In order to overcome this shortcoming, many scholars have carried out a lot of research on macroscopic mechanical behavior and microstructure evolution, but how microstructure evolution affects the macroscopic mechanical behavior of magnesium alloy is still unclear, and lack of micro-scale measurement of macroscopic and microscopic deformation. There is no consensus on the reasons for the anisotropy deformation of magnesium alloys. In this paper, the anisotropic deformation of magnesium alloy under different strain rate is studied by using in-situ real-time synchronous radiation X-ray phase contrast imaging and diffraction multi-scale measurement method. In the process of deformation of magnesium alloy, the macroscopic stress relaxation strain curve, micro-strain field and micro-diffraction pattern are simultaneously acquired. The results show that the stress relaxation strain curve, strain field and diffraction pattern evolution of the specimen under quasi-static compression loading, strain rate 5X0-4s-1, LA-c and LA-c in room temperature environment show significant difference. For LA-c samples, {1012} tensile twinning dominant plastic deformation, the stress gradient is rapidly released by twinning and the strain field becomes uniformized, and the decrease in strain localization degree effectively stimulates the increase of strain hardening rate. However, the plastic deformation in LA-c samples depends mainly on dislocation movement, dislocation is at the defect and entanglement causes strain concentration, and meso-non-uniform deformation results in a decrease of strain hardening rate. The quasi-static compressive loading and strain rate of 10-3s-1 and the macroscopic mechanical properties of magnesium alloy in high-temperature environment are studied. The micro-strain field and the micro-lattice deformation show obvious anisotropy. Due to the difference in the initial texture, the {1012} tensile uniaxial crystals dominate the plastic deformation of the LA-c samples at room temperature and high temperature, while dislocation movements are more prevalent in the LA-c samples. As the temperature increases, the number of {1012} tensile microcrystals excited in the LA-c sample is gradually decreased so that the degree of homogenization of the strain field is reduced; at high temperatures, the {1122} c + a cone slip in the LA-c sample is easier to start, so that the LA-c samples exhibit more uniform deformation at high temperatures. The {1012} tensile stressor and the cone c + aa slip can uniformize the plastic deformation by coordinating the vertical and the deformation parallel to the loading direction. The difference of non-uniformity of strain field results in a significant difference in strain hardening rate of LA-c and LA-c samples. 3. Split Hopkinson pressure rod is loaded with a strain rate of about 5. 5-103 s-1. The dynamic response of magnesium alloy is similar to quasi-static loading. The increase of strain hardening rate is effectively excited by the decrease of the degree of localization of the strain field and the decrease of strain hardening rate due to the increase of the non-uniform deformation of the strain field and the increase of the non-uniformity of the strain field. However, during the initial stage of plastic deformation, the twin dominant plastic deformation during dynamic loading, while the dominant plastic deformation under quasi-static loading is dislocation movement, indicating that the loading strain rate affects the deformation mode of magnesium alloy to some extent. The elastic-plastic transition of the strain rate of 0. 92 ~ 1. 35-0105s-1LA-c and LA-c-c samples showed obvious anisotropy, but the elastic limit was about 0.32GPa. When the impact velocity increases, the crack intensity increases with the increase of the impact velocity, and the difference is reduced; when the impact velocity increases to 400 m/ s, The fracture strength of LA-c and LA-c samples was consistent. A large number of {1012} tensile microcrystals were formed in the LA-c samples, and the number of crystals in LA-c samples was small.
【學位授予單位】:中國科學技術大學
【學位級別】:博士
【學位授予年份】:2017
【分類號】:TG146.22

【相似文獻】

相關期刊論文 前10條

1 杜賢昌;郭淑蘭;董文;徐學東;;AZ31B鎂合金A-TIG單一活性劑的設計與研究[J];熱加工工藝;2014年09期

2 杜九汪;王強;;AZ80鎂合金帶內(nèi)筋薄壁殼體擠壓新方法[J];輕合金加工技術;2014年05期

3 劉蒙恩;白莉;袁苗達;樊艷麗;;AZ31鎂合金/AgCu合金/5083鋁合金TLP擴散焊研究[J];熱加工工藝;2014年09期

4 鄭堅,,孫成友;關于材料的應變率敏感效應[J];力學與實踐;1996年03期

5 劉曉輝;張茹;劉建鋒;;不同應變率下煤巖沖擊動力試驗研究[J];煤炭學報;2012年09期

6 張萬靜;;用優(yōu)良的比率試驗機對鈦6-6-2進行高應變率試驗[J];工程與試驗;1977年Z1期

7 李正升,鄭芝蘭,王培興,張關云;低碳錳鈮鋼的熱加工性能[J];金屬學報;1985年01期

8 夏源明;袁建明;楊報昌;;纖維應變率相關的統(tǒng)計本構模型的理論與實驗研究[J];復合材料學報;1993年02期

9 包合勝;盧維嫻;董新龍;王禮立;;鑄鎂合金ZM_5-T_4本構特性的宏觀與微觀研究[J];寧波大學學報(理工版);1991年01期

10 張作梅,趙士達;不同溫度、速度條件下,G3、1Cr13鋼、鋁、鉛等塑性變形抗力的研究[J];金屬學報;1963年02期

相關會議論文 前10條

1 穆玉明;米也賽爾·阿不都熱依木;韓偉;古麗齊滿·霍加阿不都拉;;肥厚型心肌病左房收縮和舒張功能的應變率顯像研究[A];第九屆全國超聲心動圖學術會議論文集[C];2007年

2 龐利;金紅;王惠;李欣;陳旭;周振芳;;應用應變率及實時三維超聲技術評價急性病毒性心肌炎患兒左心功能的研究[A];中國超聲醫(yī)學工程學會第九屆全國腹部超聲醫(yī)學學術會議論文匯編[C];2012年

3 龐利;金紅;王惠;李欣;陳旭;周振芳;;應用應變率及實時三維超聲技術評價急性病毒性心肌炎患兒左心功能的研究[A];中華醫(yī)學會第十三次全國超聲醫(yī)學學術會議論文匯編[C];2013年

4 夏志超;楊龍;隋欣;李世鵬;王寧飛;;中應變率(10~1s~(-1)量級)設備介紹及存在問題分析[A];北京力學會第20屆學術年會論文集[C];2014年

5 吳田;郭瑞強;陳金玲;周青;;應變率顯像評價冠心病患者左室功能[A];第九屆全國超聲心動圖學術會議論文集[C];2007年

6 高繼康;鄭哲嵐;戴曉艇;曹昕陽;鄭鳳華;;定量組織速度顯像和應變率顯像對肺心病右室壁舒張功能的研究[A];2008年浙江省超聲醫(yī)學學術年會論文匯編[C];2008年

7 阮雯;孫寅光;徐怡瓊;趙勤華;張鳳如;沈衛(wèi)峰;;二維應變率顯像評價慢性收縮性左心功能不全患者心房功能[A];第九屆全國超聲心動圖學術會議論文集[C];2007年

8 吳田;郭瑞強;周青;陳金玲;;應變率顯像評價高血壓和冠心病患者左室心肌功能[A];第九屆全國超聲心動圖學術會議論文集[C];2007年

9 戚承志;錢七虎;;巖石等脆性材料動力強度依賴應變率的物理機制[A];錢七虎院士論文選集[C];2007年

10 夏s

本文編號:2290059


資料下載
論文發(fā)表

本文鏈接:http://www.sikaile.net/kejilunwen/jiagonggongyi/2290059.html


Copyright(c)文論論文網(wǎng)All Rights Reserved | 網(wǎng)站地圖 |

版權申明:資料由用戶716ff***提供,本站僅收錄摘要或目錄,作者需要刪除請E-mail郵箱bigeng88@qq.com