Fe-Mn-Al-C低密度高强度钢中有序相的性质及对钢力学性能影响的研究

发布时间：2018-01-24 04:01

本文关键词： 有序相低密度高强度钢第一性原理电子结构力学性能　出处：《昆明理工大学》2017年硕士论文　论文类型：学位论文

【摘要】：低密度高强度钢具有低密度、耐腐蚀、高强韧性等较好的综合性能,该钢在汽车、军工、化工等领域具有巨大的潜力,同时在汽车轻量化和安全性上也具有广泛应用的前景。低密度高强度钢中的有序相相主要为B2型的(Fe,Mn)Al和DO_3型的(Fe,Mn)3Al,然而这些有序相在低密度高强度钢中含量较少,且在一定条件下才会生成。由于目前关于有序相的研究比较少,因此本论文通过理论计算与实验相结合的方法,计算了 Fe-Al金属间化合物与Fe-Mn-Al合金的稳定性、电子结构、力学性质和德拜温度等,研究了 Fe-Al化合物的组织与力学性能,同时对Fe-Mn-Al-C钢的组织与力学性能进行了进一步研究。这些研究可以为低密度高强高塑性特种钢铁新材料的工业化提供理论基础与数据支持。本论文主要获得了以下研究结果:这些Fe-Al化合物、DO_3型Fe-Mn-Al合金和B2型Fe-Mn-Al合金的结合能和形成焓均为负值,表明它们具有热力学稳定性;通过力学稳定性判定条件表明这些合金具有结构稳定性。计算了这些化合物的体模量、剪切模量、杨氏模量、硬度及泊松比,研究表明:DO_3型Fe-Mn-Al合金具有较好的塑性和较低的强度,B2型Fe-Mn-Al合金的有较差的塑性和较高的强度。同时还研究了这些化合物的力学各向异性,发现它们都有较强的杨氏模量各向异性。通过对这些化合物的电子结构与德拜温度的研究,发现这些化合物的化学键主要是金属键和共价键的作用,同时也有反键作用。通过实验合成了 Fe_3Al和FeAl化合物,研究了它们的组织和与学性能,表明FeAl合金具有较高的硬度和强度,而具有较差的塑性;Fe_3Al合金具有较低的硬度和强度,但有较好的塑性。最后,还研究了 Fe-Mn-Al-C钢的组织与力学性能,研究表明该实验钢为双相钢,以奥氏体和铁素体为基体。通过XRD物相分析,发现在组织中存在B2和DO_3的有序相,即使经过较高温度的固溶处理,B2和DO_3有序相依然能够稳定存在。随着固溶温度的升高,该钢中有序相含量越来越低。通过室温拉伸力学性能的研究,表明随着固溶温度的升高材料的抗拉强度降低,而延伸率增大。因此,可以推测有序相能够提高钢的强度而降低钢的塑韧性。
[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.
【学位授予单位】：昆明理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG142.1

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