本文選題：Fe-6.5wt%Si電工鋼　切入點(diǎn)：有序相　出處：《北京科技大學(xué)》2015年博士論文　論文類型：學(xué)位論文

【摘要】：Fe-6.5wt%Si合金(又稱高硅電工鋼)具有高磁導(dǎo)率、高電阻率、低鐵損和幾乎為零的磁致伸縮系數(shù)等優(yōu)異的軟磁性能,對(duì)于提高電器效率、降低設(shè)備噪音以及節(jié)約能源等具有重要意義。但是該合金的室溫脆性和低的加工性能嚴(yán)重制約了其在工業(yè)領(lǐng)域的應(yīng)用。本課題組已經(jīng)通過(guò)逐步增塑法成功制備出0.05-0.1min厚的冷軋薄板,那么進(jìn)一步明確高硅鋼的脆性本質(zhì),深入分析影響高硅鋼塑性的因素,研究制備過(guò)程中逐步增塑機(jī)理便成為本論文的主要目標(biāo)。 本文系統(tǒng)研究了Fe-6.5wt%Si合金中有序無(wú)序轉(zhuǎn)變過(guò)程及其對(duì)各種力學(xué)性能的影響,明確了高硅鋼的脆性本質(zhì)；在此基礎(chǔ)上分析了冷卻速度及形變過(guò)程對(duì)有序相的影響,為高硅鋼塑性的改善提供了方法和思路；探索了有序相定量計(jì)算方法,研究了高硅鋼整個(gè)制備過(guò)程中有序相的演變規(guī)律,為逐步增塑法制備高硅鋼薄板提供了理論依據(jù)。得到的主要結(jié)論如下： (1)確定了Fe-6.5wt%Si合金有序無(wú)序轉(zhuǎn)變溫度,A2-B2和B2-D03的相轉(zhuǎn)變溫度分別為760℃和640℃。B2有序相是在A2無(wú)序相的基礎(chǔ)上發(fā)生Fe和Si原子的近鄰有序化而形成的,B2相的長(zhǎng)大符合經(jīng)典的晶粒長(zhǎng)大的動(dòng)力學(xué)公式；而D03有序相是在B2相的基礎(chǔ)上,進(jìn)一步發(fā)生Fe和Si原子的次近鄰有序化而形成的。當(dāng)DO3相長(zhǎng)大到一定程度,疇內(nèi)發(fā)生分解,沿100方向析出另一種Si原子占位的D03’有序相,從而形成了規(guī)則排列的條狀襯度。 (2)在D03相區(qū)做有序化處理,會(huì)使Fe-6.5wt%Si合金的力學(xué)性能惡化。將無(wú)序化后的Fe-6.5wt%Si合金分別在不同相區(qū)(B2和D03相區(qū))保溫不同時(shí)間,得到不同有序相含量的合金。在B2相區(qū)保溫過(guò)程中,流變應(yīng)力沒(méi)有明顯的規(guī)律性,合金的顯微硬度值基本保持穩(wěn)定,且均表現(xiàn)出良好的塑性：而在D03相區(qū)保溫過(guò)程中,顯微硬度與流變應(yīng)力在lh以內(nèi),隨時(shí)間的延長(zhǎng)呈上升趨勢(shì),超過(guò)lh之后,基本保持穩(wěn)定,而且合金的塑性隨著有序化時(shí)間的延長(zhǎng)是逐漸變差的,且均為脆性解理斷裂。 (3)熱處理或制備過(guò)程中快的冷卻速度,例如淬火、空冷和快速凝固,可以抑制D03脆性有序相的形成,有利于提高合金的力學(xué)性能。而在慢冷條件下,比如爐冷和普通澆鑄,D03有序相充分形成并長(zhǎng)大,有序化程度和有序相含量均很高。D03有序相的存在降低了超位錯(cuò)的可動(dòng)性,位錯(cuò)容易在晶內(nèi)或者晶界處聚集,并發(fā)生反應(yīng)形成位錯(cuò)網(wǎng)絡(luò),從而進(jìn)一步阻礙了位錯(cuò)的運(yùn)動(dòng),容易引起應(yīng)力集中,導(dǎo)致合金塑性降低,容易引起脆性穿晶斷裂或沿晶斷裂。 (4)形變過(guò)程可以破碎B2或D03有序相,不斷減小有序疇尺寸,降低有序相含量及有序度,即發(fā)生形變誘導(dǎo)無(wú)序化。形變誘導(dǎo)無(wú)序化是超位錯(cuò)滑移的結(jié)果,合金的無(wú)序化是從滑移面上的反相疇界(APBs)開(kāi)始的。大量超位錯(cuò)的運(yùn)動(dòng)會(huì)逐漸擴(kuò)大無(wú)序化面積,降低合金有序度。當(dāng)合金在高溫?zé)o序相區(qū)經(jīng)過(guò)形變后,高密度位錯(cuò)缺陷的存在將會(huì)阻礙空冷過(guò)程中有序相的形成,降低有序相的含量。 (5) Fe-6.5wt%Si合金在中溫有序相區(qū)變形的過(guò)程中表現(xiàn)出顯著的加工軟化現(xiàn)象,其加工軟化機(jī)制為形變誘導(dǎo)無(wú)序化和動(dòng)態(tài)回復(fù)。在中溫形變過(guò)程中,有序相的含量、尺寸及有序度不斷降低：在形變后期產(chǎn)生了大量的位錯(cuò)胞和亞晶組織,發(fā)生了明顯的動(dòng)態(tài)回復(fù),使位錯(cuò)密度大大降低,有效消除了部分加工硬化。兩方面的作用使合金得到了有效的軟化。 (6)嘗試?yán)秒娮友苌浞e分強(qiáng)度對(duì)Fe-6.5wt%Si合金中的有序相進(jìn)行定量計(jì)算,并給出了相應(yīng)的計(jì)算公式。通過(guò)驗(yàn)證實(shí)驗(yàn)證明了該方法的合理性和可行性。利用電子衍射積分強(qiáng)度定量法對(duì)Fe-6.5wt%Si合金整個(gè)制備加工過(guò)程中有序相的變化做定量分析。結(jié)果表明,在合金的鑄造-鍛造-熱軋-溫軋-冷軋過(guò)程中,有序相的含量是逐漸降低的,為逐步增塑法制備高硅鋼薄板提供了理論依據(jù)。
[Abstract]:Fe-6.5wt%Si alloy (also called high silicon electrical steel) has high permeability, high resistivity, soft magnetic properties of low iron loss and nearly zero magnetostriction coefficient of excellent, to improve electrical efficiency, is of great significance to reduce equipment noise and save energy. But the alloy brittleness at room temperature and low processing performance seriously its applications in the industrial field. The research group has passed gradually plasticizing process successfully prepared 0.05-0.1min thick cold rolled sheet, then to further clarify the nature of brittleness of high silicon steel, in-depth analysis of the impact factors of high silicon steel, study on preparation process of gradually plasticizing mechanism has become the main target of this thesis.
This paper studies the Fe-6.5wt%Si alloy orderdisorder transition process and its impact on the mechanical properties, the brittle nature of high silicon steel; on the basis of analysis of the influence of cooling rate and deformation phase of order, provides methods and ideas for the improvement of high silicon steel; to explore the quantitative calculation method of ordered phase on the whole, high silicon steel during the preparation of ordered phase evolution, gradually plasticizing preparation of high silicon steel sheet provides a theoretical basis. The main conclusions are as follows:
(1) determine the order disorder transition temperature of Fe-6.5wt%Si alloy, A2-B2 and B2-D03 phase transition temperature were 760 degrees and 640 degrees.B2 ordered phase is between Fe and Si atoms in A2 disordered phase based on nearest neighbor ordering and the formation and growth of B2 phase dynamics formula accord with the classic grain growth; and D03 ordered phase is in B2 phase on the basis of subneighbouring further Fe and Si atoms orderly formed. When DO3 grew up to a certain extent, in the domain decomposition, along the 100 direction precipitated another Si atom occupying the D03 ordered phase, thus forming a regular arrangement of strip contrast.
(2) do the ordering in the D03 phase, will deteriorate the mechanical properties of Fe-6.5wt%Si alloy. Fe-6.5wt%Si alloy disorder after respectively in different phase (B2 and D03 phase) for different holding time, different alloy ordered phase. In the insulation of B2 phase in the process of rheological stress the obvious regularity, the microhardness values remained stable, and showed a good plasticity: while in the D03 phase insulation process, the microhardness and the flow stress within LH, with time increased, more than LH, stable, and ductility of the alloy with the extension of the ordered time is gradually deteriorated, and are brittle cleavage fracture.
(3) heat treatment or preparation process of fast cooling speed, such as quenching, cooling and rapid solidification, can inhibit the D03 brittle phase formation, is conducive to the improvement of the mechanical properties of the alloy. In slow cooling conditions, such as furnace cooling and ordinary casting, D03 ordered phase fully formed and grew up orderly the degree and the ordered phase has a high content of.D03 ordered phase reduces the mobility of superdislocations, dislocation or easily gathered in the grain boundaries, and reacts to form dislocation network, further hampering the dislocation movement, easy to cause the stress concentration, resulting in the plasticity of the alloy decreases, easily lead to brittle transgranular fracture and intergranular fracture.
(4) the deformation process can be broken or B2 D03 ordered phase, decreasing ordered domain size, lower ordered phase content and degree of order, namely deformation induced disordering. Deformation induced disordering is super dislocation slip the disordered alloy from sliding on the surface of the antiphase boundary (APBs) began. A large number of super dislocation movement will gradually expand the disordered area, orderliness of alloys. When the alloy in high temperature disordered phase zone after deformation, high density dislocations will hinder the air cooling process of ordered phase formation, reduce the content of the ordered phase.
(5) showed a significant softening deformation process of ordered phase zone of Fe-6.5wt%Si alloy in the temperature of the softening mechanism induced by disordering and dynamic recovery deformation. In the process of warm deformation, the content of the ordered phase, the size and the degree of order decreased continuously produced a large number of dislocation cells and subgrains the organization has an obvious deformation stage, the dynamic recovery, the dislocation density is greatly reduced, effectively eliminating the part of work hardening. The two aspects of the role of the alloy has been effectively softening.
(6) try to use the electron diffraction integral intensity of ordered phases in Fe-6.5wt%Si alloy were quantitatively calculated, and the corresponding formulas are given. Experimental results indicate the rationality and feasibility of this method. The quantitative analysis of the ordered phase change by electron diffraction integral intensity quantitative method of Fe-6.5wt%Si alloy in the preparation process. The results show that the alloy casting - forging and hot rolling temperature and cold rolling process, the content of ordered phase is reduced gradually, gradually plasticizing preparation of high silicon steel sheet provides a theoretical basis.

【學(xué)位授予單位】：北京科技大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2015
【分類號(hào)】：TG142.1

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本文編號(hào)：1640810