本文關(guān)鍵詞： 電脈沖處理 純鋁 織構(gòu) 電化學(xué)阻抗 動電位極化　出處：《遼寧工業(yè)大學(xué)》2017年碩士論文　論文類型：學(xué)位論文

【摘要】：電脈沖處理技術(shù)(EPM)對金屬凝固過程的控制作用已逐漸被認(rèn)知與研究,并在工業(yè)生產(chǎn)中得到初步應(yīng)用,其中對形核后的凝固生長階段的控制是研究電脈沖處理的重要內(nèi)容之一�？棙�(gòu)是表征晶面取向變化的常用手段,了解電脈沖處理?xiàng)l件下金屬凝固生長過程中晶面演變,對了解電脈沖處理對凝固生長過程的影響機(jī)制至關(guān)重要。本文首先將電脈沖處理技術(shù)應(yīng)用于純Al熔體,考察不同脈沖電壓和不同熔體溫度對Al熔體及凝固行為的影響,利用X射線衍射與電化學(xué)阻抗以及動電位極化測試,研究脈沖處理對Al中織構(gòu)演變的作用,并研究占優(yōu)織構(gòu)成分下純鋁的電化學(xué)性能。EPM處理能夠改變Al熔體凝固生長行為,不同脈沖電壓的EPM處理后,柱狀晶生長的高度與寬度均增加,生長取向發(fā)生偏移并且出現(xiàn)等軸晶的高度相對增加;在700~800℃的溫度區(qū)間內(nèi),EPM處理時Al的熔體溫度升高可使Al定向凝固鑄錠組織中Al柱狀晶晶粒的寬度增加,且生長更加連續(xù)。EPM處理后Al熔體結(jié)構(gòu)的改變,導(dǎo)致Al(110)面生長受到抑制,生成原子面密度更小的Al(111)與Al(100)晶面。Al熔體受到EPM的作用后,α與τ取向線所構(gòu)成的空間中,α取向織構(gòu)強(qiáng)度增加,引起Al在定向凝固過程中形成的Al柱狀晶寬度的增加。另外,在經(jīng)過500 V脈沖電壓的EPM處理后Al的凝固組織中發(fā)現(xiàn)了生長取向遠(yuǎn)離τ取向的定向生長織構(gòu)。100 V與500 V脈沖電壓的EPM處理,會使Al熔體凝固形核溫度降至最低,且經(jīng)過100 V脈沖電壓的EPM處理后,結(jié)晶時間增至最大。當(dāng)Al熔體溫度為700與750℃時,經(jīng)過EPM處理后,Al熔體的凝固形核溫度降到較低的溫度;700℃熔體溫度的EPM處理,使凝固結(jié)晶時間增至最大。不同脈沖電壓的EPM處理在凝固過程中能夠調(diào)整晶面的取向,從而實(shí)現(xiàn)了Al鑄錠中的織構(gòu)控制。在熔體溫度不斷增加的過程中,EPM處理的Al熔體在凝固生長過程中形成晶面演變過程不是連續(xù)的,其凝固生長晶面的演變不是通過大量晶面的轉(zhuǎn)向而實(shí)現(xiàn)的,是由于初生晶面的改變從而直接導(dǎo)致隨后的生長過程存在明顯差異。低指數(shù)的晶面的{201}100{110}1-18的組合織構(gòu)成分的R_a明顯高于其他組合的織構(gòu)成分。隨著平均晶面原子密度的減小,組合織構(gòu)的C_a值具有逐漸增大的趨勢。陰極極化過程對具有{441}-1-18{552}115組合織構(gòu)成分的Al電極表面狀態(tài)影響較大,導(dǎo)致其腐蝕電位正移。不同的Al表面組合織構(gòu)成分中,平均晶面原子面密度越大,從而導(dǎo)致其i_(corr)的減小,進(jìn)而使具有此種平均晶面原子面密度較大的組合織構(gòu)的Al表面的耐蝕性顯著提高。
[Abstract]:The control effect of EPMs on the solidification process of metals has been gradually recognized and studied, and has been applied in industrial production. The control of solidification growth stage after nucleation is one of the important contents in the study of electric pulse processing. Texture is a common method to characterize the orientation of crystal plane. It is very important to understand the evolution of crystal plane in the process of metal solidification growth under the condition of electric pulse treatment, which is very important to understand the influence mechanism of electric pulse treatment on solidification growth process. Firstly, the electric pulse treatment technology is applied to pure Al melt. The effects of pulse voltage and melt temperature on the melt and solidification behavior of Al were investigated. The effects of pulse treatment on the texture evolution of Al were studied by means of X-ray diffraction electrochemical impedance and potentiodynamic polarization. The electrochemical properties of pure aluminum under dominant texture. EPM treatment can change the solidification growth behavior of Al melt. The height and width of columnar crystal growth increase after EPM treatment with different pulse voltage. The growth orientation is offset and the height of equiaxed crystal increases relatively. The width of Al columnar grains in Al ingot can be increased by increasing the melt temperature of Al in the temperature range of 700 鈩，

本文編號：1472735