Addition Of Grain Refiner Research Articles

Directional solidification of Cu with dispersed W nanoparticles: A molecular dynamics study in the context of additive manufacturing

Directional solidification, resulting in the development of columnar grains, is prevalent in laser-additive manufacturing of metal parts. The addition of grain refiners or inoculants enables the control of the nucleation process and columnar-to-equiaxed transition. In this study, we applied molecular dynamics simulations to investigate the directional solidification in liquid copper inoculated with tungsten nanoparticles. The interaction of the solidification front with inert nanoparticles resulted in either their engulfment in the Cu matrix or their pinning by grain boundaries. Analysis of the forces acting on the nanoparticles and the temperature field provides conditions for engulfment, determining the feasibility of copper matrix composites. By global cooling reflecting the thermal dynamics characteristics of additive manufacturing, a columnar-to-equiaxed transition can be captured at the nanoscale, with heterogeneous nucleation occurring at the nanoparticle surfaces. The conditions for the onset of heterogeneous nucleation were assessed on the basis of nanoparticle size and interpreted in terms of classical nucleation theory. Our results highlight the critical role of W-nanoparticle wetting by Cu solid grains in increasing grain refinement efficiency and suppression of columnar growth in additive manufacturing.

Enhancing the strength and structure of Al–Si alloys for biomedical applications through the addition of Sr and Zr grain refiners on secondary AlSi7Mg aluminum alloys

The biomedical industry needs Aluminium alloys with superior corrosion resistance properties for limited applications. The use of Al–Si alloys is often seen as non-bio-compatible alloys due to their lower corrosion resistance properties. The present study aims to enhance the properties of such Al–Si alloys through modification of the Si phases with Strontium (Sr) and Zirconium (Zr) through grain size modification. The present study included the preparation of an Al–Si aluminium alloy utilizing a mixture of different scraps. To refine the grain structure, variable concentrations of Sr and Zr grain refiners were added to the alloy using a stir-casting process. The qualities, including porosity, density, tensile strength, yield strength, and hardness, were assessed according to ASTM standards. The grain size and distribution of intermetallic compounds were investigated by performing a microstructural examination using scanning electron microscopy (SEM) and X-ray diffraction (XRD) techniques, to determine the impact of Sr and Zr. The results demonstrate that the inclusion of Sr and Zr grain refiners effectively enhances the grain structure, leading to enhanced microstructural and mechanical properties of the secondary aluminium alloys. This study contributes valuable insights into optimizing the grain refining process for secondary aluminum alloys, offering potential advancements in their industrial applications, particularly in the biomedical industry, where the demand for high-performance biocompatible aluminum materials is steadily increasing.

Fundamentals of Ultrasonic Treatment of Aluminum Alloys

High integrity cast aluminum components require the use of molten metal processing technologies prior to casting. These include processes such as degassing to reduce porosity, filtration to reduce inclusion content, addition of grain refiners to refine the grain structure, and the addition of chemical modifiers to alter the morphology of eutectic phases. Ultrasonic treatment (UST) is a novel processing method through which ultrasonic energy is introduced into molten metal for the purpose of degassing as well as modifying the cast microstructure. To optimize the use and applications of UST, it is necessary to examine the fundamental mechanisms and the limiting values of controlling parameters. The effectiveness of UST to perform a desired application within a molten metal is highly dependent on temperature, volume of liquid metal, and the state of the frequency in use. The mechanisms of ultrasonic energy imparted within molten metal will be discussed as well as the benefits of UST during molten metal processing.

The Effects of Cooling Rate on Microstructure Formation during Solidification of 319 Alloy

This work assesses the effect of cooling rate (T˙\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\dot{T}$$\\end{document}) on the solidification kinetics and microstructural evolution of a 319 aluminum alloy with and without the addition of Al–5 wt%Ti–1wt%B grain refiner. Directionally solidified samples were produced under various cooling rates (from 0.05 to 40 °C/s). Microstructure coarsening was then quantitatively analyzed by measuring grain size (GS) and primary (λ1), secondary (λ2) and average (λL) dendrite arm spacing. The results show that polarized optical images can be used to identify dendrite fragments between neighboring primary dendrites, allowing a more accurate microstructural analysis after the addition of grain refiner. The results also show that, for a given T˙\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\dot{T}$$\\end{document}, although GS is reduced after the addition of grain refiner, the respective values of λ1, λ2 and λL remain practically the same. In other words, the grain refiner only affects nucleation and not grain growth. Experimental growth equations are proposed to represent this behavior. Furthermore, λL is shown to be a good parameter for evaluating microstructural refinement.

Effect of Al5Ti1B and Al8B on the microstructure, wear and corrosion behavior of CuZn19Al6 bronze alloy

In this study, the effects of Al5Ti1B and Al8B grain refiners added to CuZn19Al6 manganese bronze alloy used in the aviation industry on the microstructure, mechanical properties and corrosion resistance of the alloy were investigated. Al5Ti1B grain refiner reduces the grain size of the alloy by ∼49%, while Al8B grain refiner is more limited. As a result of the addition of Al5Ti1B, an increase in hardness was observed due to the decrease in grain size, while it was determined that the Al8B grain refiner can be dissolved in the alloy and might be increased the hardness with secondary phases. It has been observed that the addition of both grain refiner increases the wear resistance while decreasing the friction coefficient of the alloy. However, no linear change was observed in both the friction coefficient and the wear rate depending on the wear test parameters. According to the potentiodynamic polarization and EIS impedance measurement results, the decrease in grain size with the addition of Al5Ti1B increased the corrosion resistance of the alloy. However, the addition of Al8B master alloy reduced the corrosion resistance of the alloy.

Grain Refinement of Cast Aluminum by Heterogeneous Nucleation Site Particles with High Lattice Matching

A number of studies have been carried out to identify the mechanism of grain refinement in cast aluminum alloys by addition of grain refiners containing potent heterogeneous nucleation site particles. Although some mechanisms and theories have been proposed, in this review, the role of heterogeneous nucleation site particles on grain refining performance will be focused. The content of this article is as follows. First, the morphology of Al3Ti particles in the Al–Ti refiners is presented, since the grain refining performance of the Al–Ti refiners is affected by the morphology of the Al3Ti particles. Evaluation methods of lattice matching between heterogeneous nucleation site and crystallized phase are, then, discussed. Since we conclude that M value is potentially applicable to predict the effective heterogeneous nucleation site, M value at elevated temperatures is described. Next, fragmentation behavior of Al3Ti particles caused by deformation of the refiners is presented, because the number density of the Al3Ti heterogeneous nucleation site particles is increased by the fragmentation of Al3Ti particles. At the same time, the morphology of the Al3Ti particles, which affects the grain refining performance, can be changed. The concept of grain refiners with high-symmetry L12 modified (Al1−xMex)3Ti intermetallic compound particles, fabrication method and some results on grain refining performance are also given. Finally, application of heterogeneous nucleation for other fields are described.

Effects of PMMT on microstructure and macrosegregation of large-sized 6061 alloy billet

The pulsed magnetic field melt treatment (PMMT) was applied in the direct chill (DC) casting of 6061 alloy billets with a diameter of 430 mm. The results indicated that the billet solidification structure was refined and homogenised. The grain size was reduced by 20.4% in the billet centre. Meanwhile, the PMMT can reduce the addition of grain refiner. The negative macrosegregation in the billet centre was reduced significantly. This can be attributed to the melt structure being changed by the energy of the pulsed magnetic field, which leads to the temperature of the melt variation and increased nucleation rate. This study may offer a promising method for the high-quality large-sized 6061 alloy billets preparation with less grain refiner.

Microstructural Evolution of a High-Strength Zr-Ti-Modified 2139 Aluminum Alloy for Laser Powder Bed Fusion

The demand for high-performance aluminum components drives research into the design of novel alloys that can be processed by laser-based additive manufacturing. In recent years, the addition of grain refiners proved to be an effective strategy to reduce the hot-cracking of high-strength Al alloys. In this study, the solidification and aging behavior of an Al2139 alloy doped with additions of Zr and Ti for L-PBF was investigated. These elements favored the formation of a fine-grained structure free of cracks. The formation of Al3(Zr,Ti) inoculants was predicted by Scheil simulations and observed as cuboidal particles in the center of α-Al grains. The microstructure of the as-built material featured fine and fully equiaxed grains, which appeared comparatively finer at the edge (300–600 nm) and coarser (0.8–2.0 μm) at the center of the molten pools. In both cases, there was evidence of Cu and Mg micro-segregations at the grain boundaries. The microhardness of 109.7 HV0.5 in the as-built state was increased to 186.1 HV0.5 after optimized T4 heat treatment, responsible for the precipitation of many rod-shaped Zr- and Ti-based second phases and quasi-spherical Cu-, Mn-, and Fe-rich particles. Prolonged exposure carried out to simulate high-temperature service caused a drop in microhardness and marked modification of the microstructure, evidenced by the rearrangement and subsequent spheroidization of Cu- and Mg-rich particles at the grain boundaries.

Effect of process variables and melt treatment conditions during cooling slope semi solid slurry generation process of Al-7Si-0.3 Mg alloy

Simulation studies on semi solid slurry preparation of A356 alloy employing cooling slope technique, with the help of an existing multiphase and multiscale model, are presented here. The constituent phases considered in the multiphase model are the liquid melt of A356 alloy, near spherical primary Al grains, and air. The numerical study features prediction of slurry morphology, for a desired set of process conditions of cooling slope slurry formation technique. In particular, the effects of melt pouring temperature into the slope, slope angle variation and addition of grain refiner and modifier within the melt on the thermophysical and morphological properties of the generated slurry are studied. Attempts are made to gain insight into the transport phenomena of cooling slope slurry generation process, with respect to volume fraction of constituent phases, morphological evolution of solidifying primary Al grains, viscosity distribution, temperature field, velocity field, macro and micro segregation, and isothermal coarsening kinetics of α-Al grains. The efficacy of the multiphase model is validated by performing relevant experiments.

Effect of Addition of Grain Refiner and Modifier on Microstructural and Mechanical Properties of Squeeze Cast A356 Alloy

Effect of Addition of Grain Refiner and Modifier on Microstructural and Mechanical Properties of Squeeze Cast A356 Alloy

Observing the Effect of Grain Refinement on Crystal Growth of Al and Mg Alloys during Solidification Using In-Situ Neutron Diffraction

The present research uses in-situ neutron diffraction to examine the effect of grain refinement on grain growth during solidification of Al-5 wt.% Cu and Mg-5 wt.% Zn alloys. The alloys were grain refined through additions of Al-5Ti-1B and Zr, respectively. The in-situ neutron diffraction experiments were carried out by heating the alloys to temperatures above the liquidus and subsequently cooling in 5 or 10 °C temperature steps to temperatures below solidus, while being irradiated by thermal neutrons. With the addition of grain refiners, grain size reductions of 92% were observed for both the Al-5 wt.% Cu and Mg-5 wt.% Zn alloys. The refined and unrefined Al-5 wt.% Cu alloys contained α-Al with Al2Cu along the grain boundary regions. Differences in Al2Cu morphology were observed in the grain refined alloys. The Mg-5 wt.% Zn alloy contained MgZn intermetallic phases with primary Mg. The refined Mg-5 wt.% Zn-0.7 wt.% Zr alloy contained Mg, MgZn and Zn2Zr phases. In-situ neutron diffraction enabled quantification of individual plane solid fraction growth for the α-Al and Al2Cu phases in the Al-Cu alloys, and for α-Mg in the Mg alloys. For the unrefined Al-5 wt.% Cu, the coarse microstructure resulted in a rapid solid fraction rise at temperatures just below liquidus followed by a gradual increase in solid fraction until the sample was fully solid. The grain-refined Al-5 wt.% Cu alloys showed a columnar to equiaxed microstructure transition and a more gradual growth in fraction solid throughout solidification. For the Mg-5 wt.% Zn alloy, the more packed (0002) and (101¯1) α-Mg plane intensities grew at a slower rate than the (101¯0) plane intensity, resulting in an irregular grain structure. With the addition of the Zr grain refiner, the Mg-5 wt.% Zn-0.7 wt.% Zr alloy had (101¯0), (0002) and (101¯1) planes intensities all increasing at similar rates, especially at the early stages of solidification. FactSage™ (version 6.4, Montréal, QC, Canada) equilibrium solidification models followed the fraction solid curves developed by tracking the fastest growing planes of the Mg alloys.

Investigation of the effect of the addition of grain refiner and modifier addition on wear properties in sand and permanent mould casting of A357 and A380 aluminium alloys

ABSTRACT The aim of this study is to improve the tribological behaviour of aluminium alloys by using grain refiner and modifier. The effects of Al5Ti1B grain refiner and Al10Sr modifier additives on friction and wear properties on A380, A357 alloys produced by pouring sand andpermanent mould casting were investigated. Abrasion tests were carried out under dry conditions against St1040 steel disc using a pin-disk system with 20 N load and 1.0 m/s sliding speed. It was determined that grain refiner and modifier additives decrease the friction coefficient and increase the wear resistance. It was determined that the samples produced by permanent mould casting method decreased the friction resistance by 9% and the abrasion resistance increased by 40% compared to the samples produced in sand mould. The lowest wear rate was obtained in A380 alloy with TiB and Sr added with a value of 4.87 × 10–11 m2/N.

Novel approach to additively manufacture high-strength Al alloys by laser powder bed fusion through addition of hybrid grain refiners

Grain refinement is effective in restraining hot tearing, reducing anisotropy, eliminating defects, improving processability, and enhancing the mechanical properties of high-strength aluminum components additively manufactured by laser powder bed fusion (LPBF). However, achieving the desired strength and ductility in LPBF-fabricated high-strength aluminum alloys post grain refinement is a predominant challenge. We have therefore designed and developed a novel hybrid grain refiner (solute/ceramic nanoparticles) which can effectively refine grains and enhance the mechanical properties of LPBF-fabricated high-strength aluminum alloys. Adding a Ti/TiN hybrid grain refiner to the LPBF-fabricated 7050 alloy can produce ultrafine grains with an average size of 775 nm, resulting in an ultimate tensile strength and ductility of up to 408–618 MPa and 13.2–8.8%, respectively. These tensile properties are comparable to those of conventional wrought 7XXX alloys. During LPBF processing, the hybrid grain refiner exhibited interesting synergistic grain refinements and strengthening mechanisms between the solute and the ceramic nanoparticles. During solidification, not only in-situ particles formed by the chemical reaction of the solute in liquid Al and the externally added ceramic nanoparticles can act as the nuclei of α-Al respectively, but also solute can inhibit the agglomeration of ceramic nanoparticles to promote their nucleation efficiency. Moreover, the strength can be further improved by doping the solute atoms at the ceramic nanoparticle/Al interface. The improvement in elongation benefited from the uniform dispersion of the various particles.

In-situ microstructural control of A6082 alloy to modify second phase particles by melt conditioned direct chill (MC-DC) casting process – A novel approach

• High shear melt conditioning in the sump during direct chill casting of A6082 billet. • Novelty of maintaining 2–7 °C above alloy liquidus as the sump thermal condition. • In-situ control of solidification during casting by intensive melt shearing. • Precise tailoring of as-cast microstructure to modify second phase particles. • Potential for industries to eliminate homogenisation and use recycled Al alloys. Controlling the formation of noncompact second phase particles during direct chill (DC) casting of aluminium alloys with grain refiner addition remains challenging, as it results in energy intensive homogenisation and deformation problems. In this work, we employed a novel strategy in the DC casting of A6082 alloy to produce billets with a fine-scale dispersion of second phase particles. The strategy involves maintaining 2–7 °C above alloy liquidus as a thermal condition in the sump by in-situ melt conditioning (MC) using a rotor-stator high-shear device operated at a critical rotation speed. As a result, in-situ control of solidification behaviour is achieved to precisely tailor the as-cast microstructure. The billet grain refinement is attained by MC-DC casting without the deliberate addition of chemical grain refiners. The microstructure of the MC-DC cast billet at the critical rotation speed showed a fine-scale dendritic structure with refined secondary dendrite arm spacing (SDAS). The solidification front proceeded with a shallow sump and a corresponding shorter solidification time, higher cooling rate, higher temperature gradient, and smooth solidification rate profile. The ideal fine-scale dendrites with low SDAS divided the remaining eutectic liquid into fine-scale and isolated liquid pockets, resulting in fine-scale, compact morphology, and uniform distribution of second phase particles in the as-cast microstructure. The MC-DC casting process showed the ability to increase the cast house production rate by increasing the casting speed without bleeding the billet. The present approach could be beneficial for eliminating or reducing the homogenisation practice and may also introduce significant flexibility in using recycled Al alloys in the industry.

Development of Al-Mg-Si alloy performance by addition of grain refiner Al-5Ti-1B alloy.

Aluminum alloys are the most essential part of all shaped castings manufactured, mainly in the automotive, food industry, and structural applications. There is little consensus as to the precise relationship between grain size after grain refinement and corrosion resistance; conflicting conclusions have been published showing that reduced grain size can decrease or increase corrosion resistance. The effect of Al-5Ti-1B grain refiner (GR alloy) with different percentages on the mechanical properties and corrosion behavior of Aluminum-magnesium-silicon alloy (Al-Mg-Si) was studied. The average grain size is determined according to the E112ASTM standard. The compressive test specimens were made as per ASTM: E8/E8M-16 standard to get their compressive properties. The bulk hardness using Vickers hardness testing machine at a load of 50 g. Electrochemical corrosion tests were carried out in 3.5 % NaCl solution using Autolab Potentiostat/Galvanostat (PGSTAT 30).The grain size of the Al-Mg-Si alloy was reduced from 82 to 46 µm by the addition of GR alloy. The morphology of α-Al dendrites changes from coarse dendritic structure to fine equiaxed grains due to the addition of GR alloy and segregation of Ti, which controls the growth of primary α-Al. In addition, the mechanical properties of the Al-Mg-Si alloy were improved by GR alloy addition. GR alloy addition to Al-Mg-Si alloy produced fine-grained structure and better hardness and compressive strength. The addition of GR alloy did not reveal any marked improvements in the corrosion properties of Al-Mg-Si alloy.

Globularization of Primary Phase of Al–7Si–0.3Mg Alloy During Cooling Slope Processing and Isothermal Holding

This study is aimed towards process design for semi-solid slurry generation of Al–7Si–0.3Mg alloy using cooling slope as a slurry maker, and subsequent isothermal holding to promote globularization of slurry microstructure. The study primarily reports globularization mechanism of cooling slope processed semi-solid slurry of the alloy, and efforts are directed to establish process control by investigating the effect of coarsening during isothermal holding on the shape, size and distribution of primary Al grains. As an outcome of this study, we propose a modified Lifshitz–Slyozov Wagner equation to quantify the effect of coarsening mechanisms prevailing during isothermal holding of the said alloy slurry. The evolution of primary phase morphology due to addition of grain refiner has also been studied and ideal processing condition is identified for the end goal of component development through rheo pressure die casting route.

Influence of Mn and TiB<sub>2</sub> on the Microstructural Evolution of the Primary α-Al Grains and Fe Containing Intermetallic in the Wrought Al-Mg-Si Alloy

The most popular aluminium alloy used for the automotive applications is the wrought-Al alloy, where its popularity arises from its intrinsic characteristics such as, excellent formability, crash resistance, corrosion resistance and excellent specific strength. In the coming decades the use of aluminium alloys is expected to increase within automotive and aerospace industries, where this will source for an upsurge in Al recycling. Problems arise during Al recycling, where there is a steady build-up of Fe content, as this is recognised as being an impurity element. Fe has very little solubility in Al in its solid state and precipitation of these Fe intermetallics (IMC), in the Al matrix decrease mechanical properties, due to the Fe IMC brittle nature. These Fe-rich IMC also have very little cohesion to the Al matrix and can separate from the Al matrix resulting in the development of voids, where the initiation of microcracks becomes ostensible when subjected to thermomechanical processing. In order to curtail the damaging effect of the Fe IMC it so of importance to alter the nucleation and growth characteristic of the Fe rich IMC during solidification. Addition of trace elements and the manipulation of cooling rates have shown to be an effective technique to alter the Fe IMC morphology. In order observe the morphological evolution of the Fe IMC, various experiments were conducted using Al-1Si-1Mg-1Fe alloy with the addition of Mn and TiB2-based commercial grain refiner. Microstructural analysis of the primary α-Al and Fe IMC are observed and the morphological evolution of the Fe IMC is analysed with respects to the addition of Mn and TiB2. How the addition of these trace elements influence the growth characteristics and chemistry of the Al melt is also presented in this work.

Improving aluminum strength with chemical modification based on titanium and boron elements

In general, Al5TiB is added to hypoeutectic Al-Si alloys with Si levels <12%. The addition of Al5Tib grain refiner to hypoeutectic Al-Si alloy has been shown to be effective in increasing the mechanical properties of the alloy. While the addition of Al5TiB grain refiner to the Al-11% Si alloy master has never been done. This study aims to determine the effect of adding Al5TiB grain refiner to the microstructure and mechanical properties of Al-Si eutectic alloys (Si 11%). The mechanical property to be known after the addition of Al5TiB grain refiner is hardness. In this research Al-11% Si material was used. Al5TiB grain refiner added to Al-11% Si material to determine changes in microstructure and the value of violence that occurs. The results showed that the addition of Al5TiB would produce a large number of fine grains with a uniform distribution and shortening the distance between dendrite arms. The results of the hardness test showed that the hardness tended to increase with increasing levels of Al5TiB grain refiner added. The decreasing in the value of hardness in the addition of Al5TiB grain refiner with 0, 15% is due to the addition of Al5TiB grain refiner has exceeded its maximum limit.

Improvement of Al–Si Hypoeutectic Cast Alloy Properties by Forging with Grain Refiner and Modifier

In this paper, the microstructures and mechanical properties (i.e., impact, tensile and hardness) of four different hypoeutectic Al–Si cast alloys were studied before and after forging process. The effect of adding various grain refiners and grain modifiers on the properties were also studied. Results indicated that, in combination with grain refiner and modifier, the hypoeutectic Al–Si cast alloys have microstructures consisting of uniformly distributed α-Al dendrites, inter-dendritic network of fine eutectic silicon and fine precipitation of CuAl2 particles in the inter-dendritic area after 50% reduction in forging. The combined addition of grain refiner and modifier to the alloy demonstrated improved mechanical properties in as-cast condition as opposed to those alloyed with individual grain refiner or modifier. The improved mechanical properties of hypoeutectic Al–Si cast alloys were linked to reduced primary dendrites, uniform distribution of eutectic silicon and inter-dendritic precipitation of small CuAl2 particles after forging.

The Effect of Al2O3 Nano Particles on Characteristics of Mg-Al-5TiB Grain Refiner Composites Produced by Stir Casting Method

High needs for light material with good mechanical characteristics made magnesium and its alloys as an alternative choice because of magnesium’s low density, 1.74 gr/cm3. However, its use is limited by its low strength and ductility. In this experiment, a fabrication process of the composite which is Mg-Al-5TiB as Matrix with the addition of Nano Al2O3 as a reinforced with volume fraction varied from 0.10 Vf-% to 0.25 Vf-% by stir casting method. The composites then were characterized by both microstructure and mechanical properties. The microstructure was analyzed by an optical microscope and scanning electron microscope link to energy-dispersive spectra to analyze the phases present in composites and confirmed by X-Ray Diffraction. The XRD shows some phases such as Mg, MgO, MgAl2O4, and B2O3. The optimum mechanical properties of composites were obtained at the addition of 0.2 Vf-% Al2O3, where the tensile strength, elongation, wear rate and impact strength were 46.1 MPa, 14%, 0.3x10-5 mm3/s, and 0.06 J/mm2. The hardness of composites was value, 40.1 HRH. The porosity maximum was found at the addition of 0.25 Vf-% with the value of 9.37% caused by nano Al2O3 particle forming clustering (porosity is related to clustered particles) and inhibiting liquid metal moving rate. The addition of grain refiner makes solidification went faster and refined the grains.