Progress in Composition Design and Preparation Methods of Large Amorphous Alloys
Amorphous alloy,also known as metallic glass(MG),is a new type of multifunctional material.It has a special atomic structure,with long range disorder and short-range order.Compared with traditional crystalline materials,amorphous alloy has a series of more excellent physical,chemical and mechanical properties,such as high strength,high hardness,high elastic limit,high wear resistance,high corrosion resistance and excellent catalytic properties,due to the absence of defects such as grains,grain boundaries and dislocation.Therefore,bulk amorphous alloys are regarded as one of the alloys with the most potential for development,showing a wide range of application prospects in the fields of micro-electro-mechanical systems,national defense equipment,precision machin-ery,aerospace,biology and medical,electronic information and chemical industry,etc,which have attracted extensive attention of many scholars.In order to prepare amorphous alloys,high external cooling rate and excellent glass forming ability are needed,so the size of amorphous alloys is much smaller than traditional metal materials,which greatly limits the engineering application of amor-phous alloys.In the early stage,bulk amorphous alloys were prepared by increasing the cooling rate.With the development of science and technology,the research on the appearance size of amorphous alloy have entered a new stage.In view of how to break through the size limitation of amorphous alloy,researchers have tried various methods and achieved some results,which will greatly promote the engineering application of amorphous alloy.These methods can be divided into alloy composition design and preparation techniques,including high-glass-forming alloy composition design based on empirical guidelines,high-throughput preparation and characteriza-tion,machine learning,low-temperature thermoplastic bonding,welding,spark plasma sintering,and 3D printing.Based on the study of existing alloys with high glass forming ability,a series of characteristics have been summarized to guide the design of alloys with high glass forming ability according to empirical rules.However,it often takes a long time to develop a new alloy component.In view of the problem of long research and development cycle of alloy components,researchers have applied the method of high-through-put preparation and characterization in the background of material genome engineering to the design of alloy components,which have greatly improved the efficiency of amorphous alloy research and development.This method can find alloy components with excellent glass forming ability and properties in a short time,and its feasibility has been proved.In recent years,with the rapid development of computing science and artificial intelligence,machine learning,as one of data analysis methods,has also been applied to material sci-ence due to its ability to analyze large amounts of and multidimensional data.Machine learning can be used for multi-dimensional anal-ysis of a large number of accumulated failed and successful experimental data.This method can be used to identify potential or elusive correlations between material data to guide the design of new alloy components.The combination of machine learning and high-through-put preparation characterization,in which the former is used to delineate the composition range,and the latter is used to rapidly screen the composition,will greatly promote the development of amorphous alloys.When the temperature rises to the supercooled liq-uid region,the amorphous alloys show superplasticity,and the viscosity decrease.According to above characteristic,low temperature thermoplastic bonding can be carried out to break through the size limitation of amorphous alloys.In addition,by means of hot com-pression and plastic deformation,researchers have successfully prepared giant bulk metallic glass(BMG)with a diameter of more than 100 mm and 3D components with complex structures.No defects are found in the samples,the density,structure,compressive properties and microhardness are consistent with those of the as-cast samples.Spark plasma sintering(SPS)can sinter powder samples into blocks with good density,which has the advantages of low sintering temperature,short sintering time,fast heating speed,amor-phous powder,which is also one of the ideas to break through the size limit of amorphous alloy.3D printing can be used to form block samples without molds,and had been used to produce bulk amorphous alloys in recent years.3D printing can break through the limit of cooling rate in the preparation process of amorphous alloy,so as to prepare BMG with larger size and complex structure.Welding technology is widely used to join all kinds of metal,and its category is also multifarious.In order to obtain larger bulk amorphous al-loys,various welding techniques have been applied to the preparation of BMG,such as ultrasonic welding,laser welding,friction welding,explosive welding and electron beam welding.All these welding techniques have their own characteristics and have been suc-cessfully utilized to weld amorphous alloys.Based on the perspective of engineering application,this paper systematically reviewed the research progress of morphology and size increase of amorphous alloys in recent years,and forecasted the development prospect of these methods for obtaining large size amorphous alloys.
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