本文關(guān)鍵詞： 有序相 低密度高強(qiáng)度鋼 第一性原理 電子結(jié)構(gòu) 力學(xué)性能　出處：《昆明理工大學(xué)》2017年碩士論文　論文類型：學(xué)位論文

【摘要】：低密度高強(qiáng)度鋼具有低密度、耐腐蝕、高強(qiáng)韌性等較好的綜合性能,該鋼在汽車、軍工、化工等領(lǐng)域具有巨大的潛力,同時(shí)在汽車輕量化和安全性上也具有廣泛應(yīng)用的前景。低密度高強(qiáng)度鋼中的有序相相主要為B2型的(Fe,Mn)Al和DO_3型的(Fe,Mn)3Al,然而這些有序相在低密度高強(qiáng)度鋼中含量較少,且在一定條件下才會(huì)生成。由于目前關(guān)于有序相的研究比較少,因此本論文通過(guò)理論計(jì)算與實(shí)驗(yàn)相結(jié)合的方法,計(jì)算了 Fe-Al金屬間化合物與Fe-Mn-Al合金的穩(wěn)定性、電子結(jié)構(gòu)、力學(xué)性質(zhì)和德拜溫度等,研究了 Fe-Al化合物的組織與力學(xué)性能,同時(shí)對(duì)Fe-Mn-Al-C鋼的組織與力學(xué)性能進(jìn)行了進(jìn)一步研究。這些研究可以為低密度高強(qiáng)高塑性特種鋼鐵新材料的工業(yè)化提供理論基礎(chǔ)與數(shù)據(jù)支持。本論文主要獲得了以下研究結(jié)果:這些Fe-Al化合物、DO_3型Fe-Mn-Al合金和B2型Fe-Mn-Al合金的結(jié)合能和形成焓均為負(fù)值,表明它們具有熱力學(xué)穩(wěn)定性;通過(guò)力學(xué)穩(wěn)定性判定條件表明這些合金具有結(jié)構(gòu)穩(wěn)定性。計(jì)算了這些化合物的體模量、剪切模量、楊氏模量、硬度及泊松比,研究表明:DO_3型Fe-Mn-Al合金具有較好的塑性和較低的強(qiáng)度,B2型Fe-Mn-Al合金的有較差的塑性和較高的強(qiáng)度。同時(shí)還研究了這些化合物的力學(xué)各向異性,發(fā)現(xiàn)它們都有較強(qiáng)的楊氏模量各向異性。通過(guò)對(duì)這些化合物的電子結(jié)構(gòu)與德拜溫度的研究,發(fā)現(xiàn)這些化合物的化學(xué)鍵主要是金屬鍵和共價(jià)鍵的作用,同時(shí)也有反鍵作用。通過(guò)實(shí)驗(yàn)合成了 Fe_3Al和FeAl化合物,研究了它們的組織和與學(xué)性能,表明FeAl合金具有較高的硬度和強(qiáng)度,而具有較差的塑性;Fe_3Al合金具有較低的硬度和強(qiáng)度,但有較好的塑性。最后,還研究了 Fe-Mn-Al-C鋼的組織與力學(xué)性能,研究表明該實(shí)驗(yàn)鋼為雙相鋼,以?shī)W氏體和鐵素體為基體。通過(guò)XRD物相分析,發(fā)現(xiàn)在組織中存在B2和DO_3的有序相,即使經(jīng)過(guò)較高溫度的固溶處理,B2和DO_3有序相依然能夠穩(wěn)定存在。隨著固溶溫度的升高,該鋼中有序相含量越來(lái)越低。通過(guò)室溫拉伸力學(xué)性能的研究,表明隨著固溶溫度的升高材料的抗拉強(qiáng)度降低,而延伸率增大。因此,可以推測(cè)有序相能夠提高鋼的強(qiáng)度而降低鋼的塑韌性。
[Abstract]:Low density high strength steel has good comprehensive properties, such as low density, corrosion resistance, high strength and toughness. It has great potential in automobile, military industry, chemical industry and so on. The ordered phase in low density and high strength steel is mainly composed of B _ 2 type Fe _ 2O _ MnAl and DO_3 type Fe _ (Fe). However, these ordered phases are less in low density and high strength steel, and can only be formed under certain conditions. Therefore, the stability, electronic structure, mechanical properties and Debye temperature of Fe-Al intermetallic compound and Fe-Mn-Al alloy were calculated by the method of theoretical calculation and experiment. The microstructure and mechanical properties of Fe-Al compounds were studied. At the same time, the microstructure and mechanical properties of Fe-Mn-Al-C steel have been further studied. These studies can provide theoretical basis and data support for industrialization of new special steel materials of low density, high strength and high plasticity. The main results of this thesis are as follows:. These Fe-Al compounds. The binding energy and formation enthalpy of DO_3 type Fe-Mn-Al alloy and B2 type Fe-Mn-Al alloy are both negative, which indicates that they have thermodynamic stability. The structural stability of these alloys was determined by mechanical stability. The bulk modulus, shear modulus, Young's modulus, hardness and Poisson's ratio of these compounds were calculated. The results show that the Fe-Mn-Al alloy has good plasticity and low strength. The b2-type Fe-Mn-Al alloy has poor plasticity and high strength. The mechanical anisotropy of these compounds has also been studied. It is found that they all have strong Young's modulus anisotropy. By studying the electronic structure and Debye temperature of these compounds, it is found that the chemical bonds of these compounds are mainly metal bonds and covalent bonds. Fe_3Al and FeAl compounds were synthesized by experiments and their microstructure and mechanical properties were studied. The results show that FeAl alloy has high hardness and strength. But with poor plasticity; Fe_3Al alloy has lower hardness and strength, but better plasticity. Finally, the microstructure and mechanical properties of Fe-Mn-Al-C steel are studied. The results show that the experimental steel is a dual phase steel. Using austenite and ferrite as the matrix, the ordered phase of B2 and DO_3 was found in the microstructure by XRD phase analysis, even after solution treatment at a higher temperature. The ordered phase of B2 and DO_3 can still exist stably. With the increase of solution temperature, the content of ordered phase in the steel becomes lower and lower. The tensile mechanical properties of the steel at room temperature have been studied. The results show that the tensile strength decreases and the elongation increases with the increase of the solution temperature. Therefore, it can be inferred that the ordered phase can increase the strength of the steel and decrease the ductility of the steel.
【學(xué)位授予單位】：昆明理工大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：TG142.1

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