Microstructure Of Ingot Research Articles

Fabrication and Microstructure of Zn-Sn Target Material Alloy

In this paper, Zn-Sn target material alloys were prepared in an electric resistance furnace. The effects of cooling condition on casting macro-defect, microstructure and segregation of ingots during solidification have been investigated by SEM and EDX analyses. The results show that the alloys casted in air-cooled and water-cooled steel moulds have not apparent casting macro-defects. The measured Sn concentration of alloys is very close to the nominal composition. The microstructures of Zn-Sn alloys are consisting of Zn-rich primary dendrite phase and divorced eutectic Sn-rich phase. The ingots solidified in water-cooled steel moulds have smaller grains than in air-cooled moulds.

Microstructure and Properties of As-Cast Cu-20Ni-5Sn Alloy

Cu-20Ni-5Sn alloy has not only high content of Ni melted point 1453°C, but also low melting point elements of Sn melted at 231.9°C, therefore, the grain structure of alloy as-cast is in perfect dendrite that lends to form segregation and inverse segregation of Sn, so that the hot rolling (cogging) processing is restricted. The influence of casting methods, cooling rate and heat treatment on the microstructures and properties of as-cast Cu-20Ni-5Sn alloy were investigated. The results show that, compared to the ingot casted in iron mold and graphite mold, the microstructure of Cu-20Ni-5Sn ingot prepared by horizontal continuous casting is the finest and the Sn segregation level is in lowest. The microstructure of the ingot casted in graphite mold is in the most perfected dendritic and with the highest segregation of Sn, the microstructure of ingot in iron molding is in the middle. The ingots must be homogenized before cold-processing. Homogenization treatment can eliminate Sn segregation and dissolve the non-equilibrium phase of ingots.

Preparation of bilayer hollow billets by horizontal electromagnetic continuous casting

The possibility for producing a bimetallic hollow billet by means of direct connection of liquid phases was investigated. Bilayer hollow billets with diameter of 83 mm and external thickness of 6 mm were fabricated by horizontal electromagnetic continuous casting. Surface features and microstructures of ingots were observed and the effect of rotating magnetic field on grain size was studied. The results show that when the casting speed is 120 mm min−1 and input current intensity is 100 A, bilayer hollow billets with well surface features combine the external and internal alloys by metallurgical bonding, and the defect free bonding interface can be seen clearly.

The Formation Mechanism of Equiaxed Crystals in Pure Aluminum Solidification Structure under the Al-Ti-C Master Alloy

The influence of different solidified velocities on the structure of pure aluminum during the process of refinement by Al-5Ti-0.6C master alloy was studied and the impact mechanism was discussed. The results show that at the same solidified velocity, with the increase of the amount of Al-5Ti-0.6C master alloy, in the solidified structure of pure aluminum, columnar crystals will gradually decrease, while equiaxed crystals will gradually increase. But in the case when the level of addition is the same, the faster the solidified velocity, the greater the number of equiaxed crystals will be in the ingot microstructure. The formation of equiaxed crystals is the result of the dual role of dissociation of crystal particles and heterogeneous nucleation of “TiC particle---Ti transition zone”.

Remelting treatment and heredity phenomenon in the formation of Fe78Si9B13 amorphous alloy

The microstructures of Fe78Si9B13 ingots including the primary master alloy (PMA) and secondary melted alloy (SMA), as well as the precipitates in the annealed amorphous ribbons spun from PMA and SMA ingots have been investigated. The presented data show that SMA ingot performances a better glass forming ability (GFA) than PMA ingot, indicating that remelting treatment can improve the GFA of Fe78Si9B13 alloy. The metastable Fe23B6 phase forms in SMA ribbons after annealing at 600°C and 700°C. The lattice parameter a0 of α-Fe in the annealed SMA ribbons is higher than that in the annealed PMA ribbons, similar to the higher a0 of α-Fe in SMA ingot than that in PMA ingot. The variation of lattice parameter a0 of α-Fe in the present ingots and annealed ribbons shows a heredity phenomenon, which is closely associated with the Fe23B6 structural units (distorted tri-capped trigonal prism clusters) in the melts.

Stereological Characterization of TiC Carbides in Bottom Skull after Melting of Ti-6Al-4V-0,5C Alloy in Vacuum Induction Furnace

This paper presents the microstructural characteristics of skull formed during melting of Ti-6Al-4V alloy with 0.5 wt% content of carbon in vacuum induction furnace using water-cooled copper crucible. The microstructure of ingot obtained as a result of skull melting is comprised of TiC carbides evenly distributed in the matrix, which consists of lamellar precipitations of α and β phases. The depth of carbon penetration towards the bottom skull was determined. At the plane section area of bottom skull, three clearly visible zones with diverse area fraction and sizes of carbides that occur in them were found. The effect of area fraction of carbides on hardness of individual zones at the bottom skull with reference to hardness of obtained ingot was also characterized.

Microstructure and mechanical properties of low frequency electromagnetic casting 7075 aluminum alloy

This work explores the microstructure of low frequency electromagnetic casting (LFEC) 7075 aluminum alloys and investigates the effect of heat treatment process on its mechanical properties via the mechanical properties test, X-ray diffraction and transmission electron microscopy. It was found that the grains of LFEC ingot were finer and more evenly distributed than that of the conventional direct chill cast (DC) ingots. The microstructure of LFEC ingot extruded kept their original as-cast structure with small and fine grains. With the same extrusion ratio, the average grain diameters of LFEC and conventional DC extruded were about 10 and 20 μm, respectively. LFEC extruded also had a better aging property, since the regime of T6 treatment peak value aging was at 120 ◦C for 24 h, the tensile strength and hardness (HV) of the LFEC extruded were 673.50 MPa and 194.62, respectively, which were all higher than those of the conventional DC extruded, indicating that the process regime can be applied in the industrial production.

Effects of the Parameters of Sloping Plate Process on Microstructures of A2017 Alloy

In this paper, effects of the parameters of sloping plate process on microstructures of A2017 alloy were investigated, and semisolid ingot of A2017 alloy was prepared. The grain size of the ingot prepared by the wavelike sloping plate is much smaller than that prepared by the flat sloping plate. The primary grain becomes rounder and smaller with the increment of the sloping plate length. High preheating temperature of the plate reduces the nucleation rate of the melt and leads to coarse microstructure. When the casting temperature is 720°C, the sloping angle is 45°, and the wavelike plate length is between 400mm and 500mm, semisolid ingot of A2017 alloy with fine and homogeneous microstructures can be obtained. The reheated microstructure of semisolid ingot is mainly composed of spherical solid grains and the melted liquids and is suitable for semisolid forming.

Extrusion of AlCuMg Alloys with Simultaneous Solution Heat Treatment

Extrusion of AlCuMg Alloys with Simultaneous Solution Heat Treatment In the work, the experiments on extrusion of high-strength aluminium alloys (2014 and 2024) with solution heat treatment on the press were performed. The experimental study describes extrudates microstructure and mechanical properties in dependence on alloy chemical composition, mode of homogenization treatment and temperature-speed extrusion conditions. The optical microscopy and SEM/EDS characterization were supported by DSC analysis, enabling to determine the solidus temperatures of the alloys. The investigations revealed that minimal contents of the main alloy additions (Cu, Mg), high-temperature homogenization and increased extrusion temperatures contributed to achieving high solutioning ratio of the alloys, guarantying improved mechanical properties of the extrudates. The high-temperature homogenization allowed achieving uniform microstructure of ingots with fine particles of intermetallic phases. The significant increase in solidus temperatures of the homogenized alloys enabled more effective solutioning on the run-out table. The maximal permissible metal exit speed was increased and the extrusion force was reduced in comparison to the conventional extrusion technology. The proposed solutions will allow for industrial producing AlCuMg extrudates of improved mechanical properties in the shortened technological cycle with heat treatment on the press.

Slow Cooling Treatment of High-Alloyed Superalloy

The very poor hot workability of high-alloyed GH4742 superalloy is represented in the aspects of very narrow available deformation temperature range, high deformation-resistant force and poor ductility. In this paper, a special heat treatment to change the ingot microstructure is proposed to improve the hot workability of the GH4742 superalloy. The' phase with a appropriate size and morphology and tortuous grain boundary were obtained by slow cooling in the ' two phases region after solution treatment. Modified microstructure induces that the hot deformation flow stress of GH4742 superalloy was decreased effectively and hot deformation plasticity was increased obviously.

Microstructure of cast ingots of Cu – V alloys after vacuum melting by different methods

The microstructure and microhardness of ingots from Cu – V and Cu – V – Fe alloys obtained by three melting methods, i.e., induction melting and electric arc melting with consumable and nonconsumable electrodes, are studied. The microstructures of the ingots are compared.

Prediction Model of Solidification Structure for Electroslag Remelting Slab Ingot

The method based on solidification mathematical model and Flemings formula was adopted to simulate electroslag remelting process. The simulation results show that the depth of the molten pool become deeper with increasing of melting speed, and when the ingot gets to the certain height, the system is in the quasi-steady state, the pool shape doesn’t change. With increasing of melting speed, secondary dendrite spacing become wider too and secondary dendrite spacing become wider gradually from the surface to center of ingot if melting speed is const. According to the simulated dendrite spacing, micro-structure of slab ingot is estimated to if meeting the demand of solidification quality, and if it can’t meeting this demand, technological conditions(melting speed)should be modified, and recalculating secondary dendrite spacing, controlling solidification structure.

A Study on the Microstructure of AISI M2 High Speed Steel Manufactured by Continuous Casting

Continuous casting has been widely applied in the production of steels and other metals. However, it has been rarely used in producing high speed steels, which are still manufactured by the conventional method of mould-casting. Thus, little is known about the microstructure of high speed steels made by the continuous casting technology. In the present work, AISI M2 steel is produced by horizontal continuous casting and the difference of solidification microstructure of ingots by different casting technologies has been examined. The results show that the networks of M2C eutectic carbides are greatly refined in the ingot by continuous casting compared to that by mould casting. Meanwhile, the morphology of M2C eutectic carbides changes from the plate-like type to the fibrous one, due to the increasing cooling rates. Compared with the plate-like M2C, the fibrous M2C in continuous casting ingots is less stable and decomposes faster at high temperatures, spheroidizing obviously after heating and refining dimensions of carbides.

Variation of the microstructure of ingots of DC cast alloy 7050 during homogenization

The structure of ingots of aluminum alloy 7050 after casting and homogenization is studied by the methods of differential scanning calorimetry, light and scanning electron microscopy, and x-ray diffractometry.

Effect of initial as-cast microstructure of AZ91D magnesium alloy on its semisolid microstructure

The effect of initial as-cast microstructure of AZ91D alloy on its semisolid microstructure has been investigated. The uniformities of semisolid microstructures of cast ingots with different diameters have also been examined. The results indicate that the initial as-cast microstructure has large effect on the semisolid microstructure: the finer the as-cast microstructure, the smaller and more spheroidal the primary particles in the resulting semisolid microstructure. For the alloys with grain sizes of 70–100 μm, one dendrite in the as-cast microstructure frequently evolves into one spheroidal primary particle in the semisolid microstructure during partial remelting. But for the alloys having grain sizes of larger than 100 μm, one dendrite always separates into two or more particles with large-size difference and irregular morphologies. The microstructure inhomogeneity of cast ingots must result in the inhomogeneity of their semisolid microstructures and these two inhomogeneities are enhanced as the ingot diameter increases. The microstructure inhomogeneity can be decreased to some extent after being partially remelted. But to obtain a uniform semisolid microstructure, it is necessary to achieve a uniform as-cast microstructure.

Effect of slow cooling treatment on hot deformation behavior of GH4742 superalloy

The very poor hot workability of high-alloyed GH4742 superalloy is represented in the aspects of very narrow available deformation temperature range, high deformation-resistant force and poor ductility. In this paper, a special heat treatment to change the ingot microstructure is proposed to improve the hot workability of the GH4742 superalloy. The γ′ phase with an appropriate size and morphology and tortuous grain boundary were obtained by slow cooling in the γ + γ′ two phases region after solution treatment. Modified microstructure induces that the hot deformation flow stress of GH4742 superalloy was decreased effectively and hot deformation plasticity was increased obviously.

MULTISCALE MODELING OF THE VACUUM ARC REMELTING PROCESS FOR THE PREDICTION ON MICROSTRUCTURE FORMATION

The final solidification structures of Vacuum Arc Remelting (VAR) ingots depend on the temperature distribution and fluid motion within the molten pool. In this paper, a three-dimensional multi-physics macroscale model for VAR is developed, based on the modular CFD software PHYSICA. This model is used to provide estimates of process parameters and to study complex physical phenomena, such as liquid metal flow with turbulence, heat transfer, solidification, and magnetohydrodynamics in the VAR process. The macromodel is coupled to a microscale solidification model. The micromodel combines stochastic nucleation and a modified decentred square/octahedron method to describe dendritic growth with a finite difference computation of solute diffusion. The resulting multiscale model allows prediction of the formation of microstructures in the solidifying mushy zone. This gives a better understanding of the whole VAR process from operational conditions to final ingot microstructures, as well as an essential first step in defect prediction.

Thermoelectric properties and microstructure of large-grain Mg2Sn doped with Ag

AbstractMg2Sn ingots, doped p-type by the addition of 0–1.0 at. % Ag, were prepared by the vertical Bridgman method at growth rates ∼0.1 mm/min. The crystalline quality and microstructure of ingots were analyzed by X-ray diffraction, scanning electron microscopy and energy-dispersive X-ray spectroscopy. The single-phase Mg2Sn ingots consist of highly oriented large grains. Measurements of the Hall coefficient, Seebeck coefficient α, and electrical conductivity σ in the temperature range 80–700 K were conducted to study the dependence on the silver content, and to determine the thermoelectric power factor α2σ which reached a maximum value 2.4×10-3 W m-1 K-2 at 410 K for 1.0 at.% Ag content.

Revisiting the glass-forming ability of Ti–Ni–Si ternary alloys

The compositional dependence of glass-forming ability (GFA) was investigated for the Ti–Ni–Si ternary alloys. Glassy ribbons varied with different thicknesses were fabricated via single-roller melt spinning. The optimized glass-forming composition was located at Ti 57Ni 35Si 8, with a critical thickness of about 200 μm for complete glass formation. By characterizing the microstructure of arc-melted ingots of the Ti–Ni–Si ternary alloys, we demonstrate that the glass formation of the Ti 57Ni 35Si 8 alloy correlates with the ( L → Ti 2Ni + TiNi + Ti 5Si 3) ternary eutectic reaction. In addition, the eutectic composition of the ( L → Ti 2Ni + TiNi + Ti 5Si 3) ternary and ( L → TiNi + Ti 5Si 3) pseudo-binary eutectic reaction was determined to be in the vicinity of Ti 63Ni 31Si 6 and Ti 53Ni 37Si 10, with the invariant reaction temperature at 1243 and 1424 K, respectively.

Investigation of Homogenization Treatment in Al- Li- Cu- Zr Alloys

Aluminum-Lithium alloys were developed as major replacements for existing aluminum alloys to reduce the weight of aircraft and aerospace structures. Mechanical properties of Al-Li alloys greatly depend on solidification conditions. Other than reducing the microsegregation, homogenization treatment has other effects on the microstructure of Al-Li ingots. In this research, effects of homogenization treatment at constant temperature (500°C) on the precipitation in the microstructure of Al-1Li-3Cu-0.1Zr (wt %) and Al-2Li-3Cu- 0.1Zr (wt %) specimens have been investigated. Results show that homogenization at 500°C for 24 hours not only increases the hardness and phases precipitating in grain but also reduces microsegregation of Fe in grain boundaries.