Application of 3D Balanced Growth Theory to the Formation of Bulk Amorphous Alloys

Since the emergence of amorphous alloys as a new class of materials, efficiency improvements have been made in optimizing the fabrication process, the mechanization of alloy formation, and the size of the alloys themselves. Amorphous alloys have been used in precision instruments as they possess excellent magnetic properties, corrosion resistance, wear resistance, high strength, hardness, toughness, high electrical resistivity, and electromechanical coupling properties. Because their hysteresis losses are lower than those of traditional transformer cores, the conversion efficiency of equipment has been significantly improved, thereby saving energy and protecting the environment. Hence, amorphous iron cores have replaced traditional materials. Amorphous alloys also show excellent performance as anti-corrosion and wear-resistant coatings. The process of preparing amorphous alloys starts with an amorphous alloy film obtained by evaporation deposition and then proceeds to the use of a high cooling rate ribbon spinning method to finally obtain a thin strip of an amorphous alloy. A widely used method of copper mold suction casting is then used to prepare the bulk amorphous alloy. The sizes of amorphous alloys have been continually increasing, which has resulted in increasingly serious challenges, such as cooling rate and thermal stability limitations. In addition, crystals can form at low cooling rates. The latent heat of crystallization is released when crystals are formed, which causes damage to the amorphous area so that the size of amorphous alloys is reduced. Because of these difficulties, new processes that eliminate the cooling rate gradient, such as 3D additive manufacturing, ultrasonic production, and mold design, combined with the concept of “entropy control” component design and the economic theory of “balanced development,” lead to a three-dimensional bulk amorphous alloy being proposed. The theory of balanced growth provides a new concept for the development and application of bulk amorphous alloys. This review offers a retrospective view of recent studies of amorphous alloys and provides a description of the formation of amorphous alloys and amorphous phases and the criteria required to predict the successful formation of amorphous alloys. Then, we address the problem of size limitation confronting current production methods. The three-dimensional balanced growth theory of bulk amorphous alloys was formulated from a flexible adaptation of the balanced growth theory of economics. We have confidence that the production and development of bulk amorphous alloys have a bright future.

The forming and crystallization behaviors of Zr50Ti5Cu27Ni10Al8 bulk amorphous alloy by laser additive manufacturing

Due to the small size and serious crystallization, the wider application of amorphous alloy materials is limited. In this paper, the bulk amorphous alloy with the size of 15 mm × 15 mm × 12 mm was made by selective laser melting technology. The characters of the composition and structure of the as-prepared bulk amorphous alloy and the thermal effect of the preparation process were analyzed. The results showed that the cooling rate of both the molten pool and the heat affected zone were much higher than the critical cooling rate of the amorphous alloy and, therefore, the cooling rate was not the reason for the crystallization in this experiment. The molten pool of the formed amorphous alloy block was completely amorphous. Due to the accumulation of structural relaxation, crystallization occurred in the heat affected zone, but the amorphous structure was still dominant. The increase in deposition layer had no obvious effect on crystallization.

Influence of Isothermal Heating on the Curie Temperature of FeCoB Bulk Amorphous Alloy

The article presents the results of research on the thermal treatment of amorphous alloys. As part of the work, an alloy with a chemical composition Fe63Co8Y8W1B20 was produced by rapid cooling. The method used to aspirate the liquid alloy into the copper mold was used. The produced material was subjected to annealing at 940K for 10 minutes. The alloy, after solidification and after heat treatment, was subjected to structure testing by means of X-ray diffraction. The soaking process led to the partial crystallization of the amorphous precursor. Using the Faraday magnetic balance, curves of the magnetic saturation polarization as a function of temperature were recorded, on the basis of their analysis, the Curie temperature of the produced materials was determined. Using the vibration magnetometer, the primary curves of magnetization and static magnetic hysteresis loops were measured. The alloy after the soaking process was characterized by higher Curie temperature and magnetically hard properties. The test results confirm the possibility of modifying the magnetic properties of high-temperature alloys through a suitably designed heat treatment.

Structure, Core Losses, Curie Temperature, Defects in the Structure of the Bulk Amorphous Alloy Fe55Co15W2Y8B20

This paper presents studies relating to the structure and soft magnetic properties of the bulk amorphous alloys Fe55Co15W2Y8B20. Samples were made using the method of injecting a liquid alloy into a copper water-cooled mold in the form of plates. The structure and microstructure were examined using X-ray diffractometry. Magnetic properties were investigated from static and dynamic measurements. For the samples, the core losses were measured. The influence of structure defects on the magnetization process in strong magnetic fields was also investigated. For this purpose, the theory developed by H. Kronm�ller was used. It was shown that the magnetization process in strong magnetic fields is associated with two-dimensional defects, so-called pseudo-location dipoles.

Effect of Niobium and Yttrium Modified Ti-Based Bulk Amorphous Alloy on Correlation of Plastic Deformation Energy and Ductility

A series of Ti40Zr25Cu9Ni8Be18)100-xTMx (x = 0, 1, 2, 3, 4 at.%, TM = Nb, Y) Bulk amorphous alloys were designed and prepared using the copper mold casting method. The microstructures, glass forming ability and mechanical properties of the alloys were investigated by means of X-ray diffractometry (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), differential scanning colorimetry (DSC), depth-sensitive nanoindentation and uniaxial compressive test. The Bulk amorphous alloys with different ductility were investigated by measuring their plastic deformation energy (PDE) of the first pop-in events during loading. The relationships between the PDE value, shear band formation and ductility in Bulk amorphous alloys have been investigated. The results show that the PDE value decreases by the Nb addition and promotes the generation of multiple shear bands easily, which increase the fracture strength and plasticity significantly. Substituting Nb with Y has exactly the reverse effect. A useful rule for preparing of Bulk amorphous alloys with high plasticity is herein proposed, whereby the chemical composition of the Bulk amorphous alloys can be tailored to possess a lower PDE value.

Synthesis of Bulk Amorphous Alloy from Fe-Base Powders by Explosive Consolidation

A Fe61Cr2Nb3Si12B22 amorphous alloy rod sample of 8.8 mm diameter has been successfully prepared through explosive consolidation. The structure and thermal stability of the as-synthesized sample have been analyzed through X-ray diffraction (XRD) and differential scanning calorimeter (DSC) analysis. The results demonstrate that the sample still retains an amorphous structure, and the glass transition temperature (Tg), the crystallization onset temperature (Tx), the supercooled liquid zone (ΔTx) (Tx − Tg) and the reduced glass transition temperatures (Trg) (Tg/Tm) are 784 K, 812 K, 28 K, and 0.556, respectively. Its microstructure has been investigated by optical microscopy (OM) and scanning electron microscopy (SEM). The average microhardness of the alumina compact is about 1069 HV.