本文關(guān)鍵詞： σ相 拓?fù)涿芏严?釩鐵 原子半徑比 電子因素　出處：《上海大學(xué)》2016年博士論文　論文類型：學(xué)位論文

【摘要】：通常情況下結(jié)構(gòu)材料,特別是含有過(guò)渡金屬元素的鈷基或鎳基高溫合金以及高鉻鐵素體鋼等材料中,拓?fù)涿芏薛蚁嗟某霈F(xiàn)將嚴(yán)重破壞其性能,研究σ相的形成機(jī)理具有重要的科學(xué)意義及工程實(shí)用價(jià)值。深入認(rèn)識(shí)該相的形成機(jī)理還有助于更好理解過(guò)渡金屬的合金化行為,實(shí)現(xiàn)對(duì)其析出進(jìn)行調(diào)控,可以有效規(guī)避該相對(duì)材料性能可能造成的致命危害。迄今為止,對(duì)σ相的形成規(guī)律及機(jī)理認(rèn)識(shí)尚不清晰,相關(guān)研究主要集中在電子濃度及電負(fù)性等因素,較少涉及原子尺寸。單純從電子因素角度出發(fā)的相關(guān)研究并不能解釋?duì)蚁嗟男纬蓹C(jī)理且欠缺物理科學(xué)意義。本論文提出二元過(guò)渡金屬σ相的形成同時(shí)受制于電子因素和原子尺寸因素,其化學(xué)鍵合為共存的金屬鍵和非飽和共價(jià)鍵,后者居主導(dǎo)地位,正是由于共價(jià)鍵的存在并配合以恰當(dāng)?shù)脑映叽绮艜?huì)導(dǎo)致拓?fù)涿芏薛蚁嗟纳�。本論文提出采用價(jià)電子總數(shù)(VET)概念描述過(guò)渡金屬σ相中的化學(xué)鍵合,基于金屬玻璃、二十面體準(zhǔn)晶和拓?fù)涿芏严嘣诙坛逃行蚍秶鷥?nèi)局域結(jié)構(gòu)非常相似的特點(diǎn),引入金屬玻璃高效堆積模型,提出原子尺寸參數(shù)R=rs/rl和1/R=rl/rs(rs和rl分別為較小原子和較大原子的半徑)用以表征Frank-Kasper配位多面體形成的幾何要求以及對(duì)σ相形成的影響。結(jié)果表明:在限定過(guò)渡金屬范圍內(nèi),12≤VET≤15能夠涵蓋目前所有存在σ相的二元合金體系,在此范圍內(nèi)滿足0.896R0.955、1.0471/R1.116或0.976R1與11/R1.025條件時(shí)將有利于σ相的形成。在12≤VET≤15的范圍內(nèi),上述幾何條件還可以有效區(qū)分σ相,Laves和μ相。將該方法拓展至過(guò)渡金屬二元系中的Laves相,我們進(jìn)一步提出了d電子總數(shù)(DET)參數(shù),發(fā)現(xiàn)1/R1.116可以作為L(zhǎng)aves相液相析出的必要條件之一,滿足該條件且處于5DET10范圍內(nèi)的過(guò)渡金屬二元系傾向于形成Laves相�；讦蚁嘈纬蓪�(duì)應(yīng)著特定的原子尺寸參數(shù)范圍這一特性,我們提出通過(guò)引入原子尺寸與σ相二元系組元差異較大的第三元素,通過(guò)造成原子尺寸參數(shù)的顯著改變進(jìn)而影響σ相的穩(wěn)定性,最終實(shí)現(xiàn)抑制σ相析出的目的。在Fe-V合金體系驗(yàn)證實(shí)驗(yàn)結(jié)果表明,較大原子半徑Al元素引入后可以有效抑制σ相的形成,且Al含量的臨界成分與理論計(jì)算值吻合較好。相關(guān)研究成果為二元、三元甚至多元合金中σ相的析出控制提供了一種新的思路。針對(duì)現(xiàn)有直筒爐電鋁熱法冶煉釩鐵出現(xiàn)的合金強(qiáng)度高,難破碎及細(xì)粉率高的難題,本論文基于這一思路提出了一種新的梯度式電鋁熱冶煉釩鐵的工業(yè)化生產(chǎn)技術(shù),該技術(shù)在工業(yè)化實(shí)際生產(chǎn)實(shí)踐中顯著改善了電鋁熱法冶煉FeV50的破碎性能。
[Abstract]:In general, structural materials, especially cobalt-based or nickel-base superalloys containing transition metal elements and high-chromium ferrite steels, the appearance of topological dense 蟽 phase will seriously damage their properties. It is of great scientific significance and practical value to study the formation mechanism of 蟽 phase. It is also helpful to understand the alloying behavior of transition metals and to regulate the precipitation of transition metals. So far, the formation law and mechanism of 蟽 phase are not clear, and the related studies mainly focus on the factors such as electron concentration and electronegativity, etc. Atomic size is less involved. The related studies from the angle of electronic factors alone can not explain the formation mechanism of 蟽 phase and lack of physical scientific significance. In this paper, it is proposed that the formation of 蟽 phase in binary transition metals is constrained by electrons at the same time. Factor and atomic size factor, Their chemical bonds are coexisting metal bonds and unsaturated covalent bonds, the latter being dominant. It is due to the existence of covalent bonds and the proper atomic size that the topological dense stack 蟽 phase is formed. In this paper, the concept of valence electron sum (VET) is used to describe the chemical bonding in the transition metal 蟽 phase, which is based on metallic glass. The local structure of 20 hedron quasicrystal and topological dense phase is very similar in the short range order range, so the metal glass high efficiency stacking model is introduced. It is proposed that the atomic dimension parameters Rnrsrl and Rnrrrrr _ s and r _ l are smaller atoms and larger atomic radii respectively) to characterize the geometric requirements of the formation of Frank-Kasper coordination polyhedrons and their effects on the formation of 蟽 -phase. The results show that the transition metal norm is limited to the transition metal norm. Weinai 12 鈮，

本文編號(hào)：1522864