元素掺杂对储氢容器用高强钢性能影响的第一性原理和分子动力学模拟

First principles and molecular dynamics simulations of effect of dopants on properties of high strength steel for hydrogen storage vessels

高压气态储氢是当前氢能储运的重要方式,而高强钢材料则是储氢容器主要采用的材料之一.然而,其内部杂质元素和固有缺陷常导致其力学性能下降,从而降低了容器的承压能力和存储寿命.目前元素掺杂对于高强度钢力学性能的影响机制尚不完全明确,基于此,本文应用第一性原理计算模拟方法研究了Fe-M及Fe-C-M(M=Cr,Mn,Mo,As,Sb,Bi,Sn,Pb)体系中元素掺杂对其机械性能的影响.结果表明,Mn掺杂使得高强钢的弹性模量、体模量和剪切模量等增强,而其余元素的引入均使得高强钢的3种模量减弱,其中非过渡金属元素对3种模量的影响大于过渡金属元素.电子结构分析表明,过渡金属元素与Fe晶格有着更好的相容性.分子动力学模拟结果进一步显示H原子的注入显著地破坏了Fe多晶掺杂C,Cr,Mn元素体系的晶格有序性,而Cr元素的掺入则可以显著提升体系的位错密度.综上,本文探究了掺杂元素对单晶和多晶Fe力学性能的影响,对Fe基材料掺杂及缺陷对强度影响的机理研究具有较强的指导意义.

High-pressure gaseous hydrogen storage is an important way of hydrogen energy storage and transport at present,while high-strength steel material is one of the main materials used for hydrogen storage vessels.However,their internal doping elements and inherent defects often lead their mechanical properties to decrease,thus reducing the pressure-bearing capability and storage life of the vessel.At present,the mechanism of doping elements influencing the mechanical properties of high-strength steels is still unclear.In this work,a firstprinciples approach is used to study the influence of elemental doping(Cr,Mn,Mo,As,Sb,Bi,Sn,Pb)on the mechanical properties of Fe single crystals and Fe-C systems.The results show that among the above elements,Mn doping can increase the elastic modulus,bulk modulus,and shear modulus compared with those of pure Fe,while the doping by remaining elements will reduce the three moduli above,with the non-transition metal elements having a greater effect on the three moduli than the transition metal elements.Electronic structure analysis shows that the transition metal elements have better compatibility with the Fe lattice.Molecular dynamics results further show that the injection of H atoms significantly disrupts the lattice ordering of the Fe polycrystalline doped by C,Cr,and Mn elements,while the doping of Cr elements can significantly enhance the dislocation density of the system.The effects of doping elements on the mechanical properties of single-crystal and polycrystalline Fe,which are studied in this work,are of great significance in guiding the mechanistic study of the effects of doping and defects on the strength of Fe-based materials.