摘要
采用分子动力学方法对 6种不同压强下Pd82Si18 高温熔体快速凝固形成非晶固体的过程进行模拟,并采用团簇类型指数法和逆向追踪法对其进行微结构特征和遗传演化分析.研究结果表明:加压能够提高体系的玻璃转变温度,在高压条件下,凝固形成的结构中存在大量的二十面体,中心原子为Pd的二十面体与中心原子为Si的二十面体更易形成嵌套共享联结中程序.遗传分析结果表明加压有利于提高团簇的遗传起始温度和遗传分数,以Si原子为中心的团簇比以Pd为中心的团簇具有更强的遗传能力,对玻璃形成能力的影响更大.
Abstract
Compared with traditional glass,metallic glass(MG)has excellent properties,such as high strength,high hardness,high fracture toughness,good soft magnetic properties and corrosion resistance due to its unique structure.Such properties enable it to be used in optics,electronics,construction and other fields,making it a highly promising new material with great application potential.As the properties of amorphous alloys are closely linked with their local structures,microstructure characteristics have always been a research focus in the amorphous field.Previous studies show that the onset temperature of heredity and the hereditary fraction of characteristic clusters can be used to effectively evaluate the glass-forming ability.In order to obtain the relationship between the microstructure characteristic and cluster evolution of amorphous alloy,and reveal the formation of glass,the glass transition processes of the Pd82Si18 alloy under different pressure conditions are simulated by using the molecular dynamics method,and the heredity and evolution of the Pd82Si18 amorphous alloy are analyzed by using the cluster-type index method and the reverse tracking method.The simulation results show that the glass transition temperature of the Pd82Si18 alloy can be increased when the pressure is higher,and a large number of icosahedra are formed in the solidified alloy when the pressure is sufficiently high.Icosahedron is a kind of structure that widely exists in amorphous materials and has been studied for quite a long time.In this work,a detailed comparative analysis of two icosahedra is conducted and the heritability of clusters with different chemical compositions under high pressure is studied.The results show that it is easier for icosahedra with central atom Pd and those with central atom Si to form a medium-range order in the Pd82Si18 amorphous alloy.An increase in pressure conduces to the increase of both onset temperature of heredity and hereditary fraction.Combined with the results of cluster heredity analysis at 0 GPa,the Si-centered clusters have stronger heritability than Pd-centered clusters,thus the former ones have a greater influence on the glass-forming ability.These findings are of significance in understanding the relationship between microstructure evolution and glass formation,and also providing certain guidance for designing amorphous alloys.
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