本文選題：晶內(nèi)鐵素體 + 三維形貌��； 參考：《華北理工大學(xué)》2017年碩士論文

【摘要】：采用掃描電鏡、拉曼光譜分析儀、高溫淬火相變儀和高溫共聚焦顯微鏡分別研究了夾雜物的尺寸和相組成成分、連續(xù)冷卻的速度、奧氏體晶粒的尺寸在晶內(nèi)鐵素體形核過程中所起的作用。同時(shí)將聚焦離子束與電子背散射衍射結(jié)合,采用連續(xù)截面-計(jì)算機(jī)輔助三維重建的技術(shù)建立晶內(nèi)鐵素體的三維空間模型,揭示了其在三維空間層面上的形貌特征、聯(lián)鎖組織的形成原因并通過EBSD的分析手段分析了它的取向關(guān)系變化,進(jìn)而對晶內(nèi)鐵素體的形核機(jī)理做了進(jìn)一步的研究。主要研究結(jié)果如下:夾雜物誘導(dǎo)鐵素體形核的能力因其尺寸的不同而有所差別,其尺寸增加時(shí)它的形核率是逐漸增加的,并存在一個(gè)峰值,3~4μm是最佳尺寸。典型的有效夾雜物的心部為Ti2O3和鋁氧化物,MnS在其外部析出,從而形成貧錳區(qū)。在0.3~3℃/s這一范圍內(nèi)能獲得針狀鐵素體,其中1℃/s最佳。奧氏體晶粒的平均尺寸正比于保溫時(shí)間。晶內(nèi)鐵素體三維空間上的形貌多樣,包括三棱柱狀、板條狀、等軸薄片狀,甚至表現(xiàn)為不規(guī)則形狀。較大尺寸的鐵素體,它不是由某一個(gè)個(gè)體長大形成,而是由若干個(gè)小鐵素體組合形成。鐵素體融合長大的特點(diǎn)是長大后它的邊界平直、光滑,表面也較為平整,沒有鐵素體之間的分界線;鐵素體相互碰撞長大的特點(diǎn)是它們的邊界并不平直、光滑,分界線清晰且表面凹凸不平。鐵素體在生長時(shí)發(fā)生激發(fā)形核、碰撞、交叉現(xiàn)象,從而形成聯(lián)鎖組織。該組織內(nèi)部取向差較小,絕大多數(shù)在2°以內(nèi)而其邊界的取向差較大,呈大角度晶界彼此分開。對于此實(shí)驗(yàn)鋼,存在4種形核機(jī)制共同促進(jìn)晶內(nèi)鐵素體的形成。夾雜物作為惰性介質(zhì)的表面,提供適宜的形核地點(diǎn)和晶核形成的驅(qū)動力。MnS和鐵素體間較小的錯(cuò)配度促進(jìn)了晶內(nèi)鐵素體晶核的形成。MnS在Ti2O3表面沉淀析出形成貧錳區(qū)以及大量的激發(fā)形核都可加速晶內(nèi)鐵素體的形成。
[Abstract]:The size and phase composition of inclusions and the rate of continuous cooling were studied by scanning electron microscope, Raman spectrum analyzer, high temperature quenching phase transformation instrument and high temperature confocal microscope, respectively.The role of austenite grain size in the nucleation of intracrystalline ferrite.At the same time, by combining focused ion beam with electron backscattering diffraction, the three-dimensional spatial model of intragranular ferrite was established by using continuous cross-section and computer aided three-dimensional reconstruction technique, and its morphology characteristics at the three-dimensional level were revealed.The formation reason of interlocking structure and the change of orientation relationship of interlocking structure were analyzed by means of EBSD, and the nucleation mechanism of intracrystalline ferrite was further studied.The main results are as follows: the ability of inclusions to induce ferrite nucleation varies according to its size, and the nucleation rate increases gradually when the size increases, and there is a peak value of 3um 4 渭 m as the optimum size.The typical core of effective inclusions is Ti2O3 and aluminum oxide (MNS) precipitated from the outside of the inclusions, thus forming the manganese poor zone.Acicular ferrite can be obtained in the range of 0.3 鈩，

本文編號：1748878