Grain Refinement Of Aluminum Research Articles

Grain Refinement of Aluminum and Aluminum Alloys by Sc and Zr

Rare earth elements and transition elements are widely used in aluminum alloys, magnesium alloys and copper alloys due to their unique microalloying effects. With regard to in-depth research on the grain refinement characteristics of rare earth elements and transition elements, the combination of grain refinement and microalloying in the master alloys has a great impact on the theories and technical research of refinement, and the broadening of the application field of master alloys. This paper first summarizes the grain refinement mechanisms and analyzes the effects of rare earth elements and transition elements on the grain refinement of aluminum and aluminum alloys, and summarizes the elements suitable for the preparation of Al-M master alloys and their refinement mechanism.

Grain Refinement Mechanisms of TiC0.5N0.5 Nanoparticles in Aluminum.

In this study, TiC0.5N0.5 nanoparticles (NPs) are shown to induce a remarkable grain refinement of aluminum at various cooling rates. The grain refinement mechanisms are systematically investigated by microstructure observation, edge-to-edge matching (E2EM) model prediction, and first-principles calculations. The experimental results suggest that as the cooling rates increase from 10 K/s to 70 K/s, a transition from intergranular to intragranular distribution of NPs occurs and the Al/TiC0.5N0.5 interface varies from incoherent to coherent. Based on the E2EM analysis combined with first-principles calculation, it is found that TiC0.5N0.5 can act as a potent nucleant for the heterogeneous nucleation of α-Al. By analyzing the NP effects on the nucleation and growth of α-Al, the grain growth restriction and nucleation promotion mechanisms are proposed to elucidate the refinement phenomena at low and high cooling conditions, respectively.

Grain refinement of aluminium 4032 alloy with the impact of vibration using Taguchi technique and analysis of variance (ANOVA)

The major criteria covered in this study are Grain Refinement parameters and tensile strength of Aluminum 4032 alloy using the Taguchi technique and analysis of variance. The Taguchi technique of orthogonal L9 design experiment is carried out utilising an orthogonal array to define good refinement on alloy material and decrease vibration error for output prediction. Variation of supply input DC voltage from 20, 23, 26 V, amplitude from 4, 5, 6 V, and frequency from 15, 30, 45 kHz. With a water supply around it and copper coil wrapping on the outside circumference, the die was ready for the refining process. The refining process focuses on the alloying components Si, Fe, Cu, Zn, Mg, Ni, and Cr. Analysis of variance (ANOVA) is a statistical approach for determining the best level of variables for the verification of the optimal design parameters through confirmation tests. It is a decision tool for identifying the variation of process parameters. The goal of this research is to use vibration to improve tensile strength, hardness, and grain size refinement.

Effect of Adding Lanthanum to Al – 5% Ti – 1% B Master Alloy on the Efficiency of Grain Refinement in Aluminum and Al – 7% Si Alloy

Effect of Adding Lanthanum to Al – 5% Ti – 1% B Master Alloy on the Efficiency of Grain Refinement in Aluminum and Al – 7% Si Alloy

The grain refinement of aluminium by a new as-cast Al–Ti–TiCN composite

A new type of composite refiner Ti/TiCN is prepared by loading submicron-TiCN particles onto Ti micron-particles and added to industrial pure aluminium. Refining mechanism has been characterised in detail by optical microscopy, scanning electron microscopy and transmission electron microscopy coupled with energy disperse X-ray spectra. These experimental results show that Ti/TiCN inoculation is more effective in refining pure aluminium than Ti and TiCN added separately. The relationship between grain size and growth restriction factors of aluminium matrix containing Ti/TiCN refiner is d = 70.2 + 1190.8/Q. According to the free growth theory, aluminium matrix with Ti/TiCN inoculation has the largest solidification driving force to promote grain nucleation under the same growth restriction factors (Q = 0.5,1, 5, 12, 20 K) compared to Ti and TiCN refiners.

Experimental investigation on the effect of microstructure modifiers and heat treatment influence on A356 alloy

The use of aluminum and its alloys has grown dramatically due to the demand for increased performance and fuel economy. Cast aluminum alloys are light weight and can be cast into complex shapes and thus they have attracted significant attention as potential replacements for castiron and steel in bulky components. Compared to other aluminum alloys, refined A356 alloy is particularly attractive for various automotive applications. Grain refinement of aluminum gives a number of technical advantages, including reduced cracking, better homogeneity, better mechanical deformation characteristics and improved mechanical properties. Microstructural study is carried out to analyse he mechanical properties of the composite. In the present work, cast A356 alloy with added copper was studied with their unique mechanical behaviour and microstructure. This is carried out in both as cast condition and heat treated condition and properties are investigated.

Grain refinement of 24 karat gold (99.99 wt.% pure) and 22 karat gold (Au-5.8wt.%Cu-2.5wt.%Ag) by Au-6wt.%Ti grain refiner

In this paper, the 24 karat (99.99 wt.% pure) and 22 karat gold (Au-5.8wt.%Cu-2.5wt.%Ag) were grain refined with Au-6wt.%Ti master alloy and the mechanism of grain refinement was studied. The Au-6wt.%Ti master alloy containing Au2Ti and Au4Ti intermetallic particles was added into 24 karat and 22 karat gold at various addition levels of Ti (0.1, 0.2 and 0.3 wt.%) for grain refinement. The intermetallic particles undergo peritectic reaction with liquid Au in sequence to nucleate α-Au solid. It is observed that both the 24 karat gold and 22 karat gold showed efficient grain refinement at the lowest addition level of Ti (0.1 wt.%). However, 22 karat showed better grain-refining efficiency than 24 karat at all addition level of Ti studied. The mechanism of grain refinement of gold in this study matches with the “Peritectic theory” and “Solute paradigm” proposed for the grain refinement of aluminium. It is also observed that increasing the master alloy addition level to 0.2 and 0.3 wt.% Ti coarsening in the grain size in both 24 karat and 22 karat, but significant in the case of 24 karat gold due to recalescence effect. The grain-refined 24 karat and 22 karat gold at 0.1 wt.% Ti showed improvement in the hardness in comparison to the un-grain refined one.

Grain refinement in ultrasonicated binary aluminium alloys

Abstract Combined effect of solute concentration and ultrasonic treatment on the grain refinement of aluminium based alloys is studied. Silicon, copper, and nickel solutes are used. Upon ultrasonic treatment, grain refinement in Al-3 wt.%Ni alloy is more pronounced than that in Al-3 wt.%Si alloy, although the growth restriction factor of solute silicon is twice that of nickel in pure aluminium. These observations spurred this investigation about the grain refinement mechanisms operating in Al-based hypoeutectic alloys. Grain refining efficiency of different solutes is analyzed using the growth restriction factor and constitutional supercooling parameter, both calculated from Scheil-Gulliver solidification simulation. It is observed that grain refinement occurring from ultrasonic treatment in near-eutectic alloys is better explained by using the constitutional supercooling parameter rather than the growth restriction factor.

A New Understanding Toward Effect of Solute Ti on Grain Refinement of Aluminum by Al-Ti-B Master Alloy: Kinetic Behaviors of TiB2 Particles and Effect of Solute Ti

实验研究了Ti添加量对Al-Ti-B中间合金细化工业纯Al晶粒效果的影响,建立了Al熔体中TiB_2粒子动力学行为模型,模拟分析了Al-Ti-B中间合金细化工业纯Al过程中TiB_2粒子的溶解、粗化和快速长大行为及溶质Ti的影响。实验和模拟结果表明,Al-Ti-B中间合金细化工业纯Al过程中,TiB_2粒子的动力学行为对中间合金细化能力的影响不可忽视,溶质Ti能有效抑制Al熔体中TiB_2粒子的溶解、粗化和快速长大行为,影响Al-TiB中间合金的细化能力。

Microstructures and Properties Evolution of Al-Cu-Mn Alloy with Addition of Vanadium

The effect of the vanadium addition on the microstructure, the precipitation behavior, and the mechanical properties of the Al-5.0Cu-0.4Mn alloy has been studied. The as-cast Al-5.0Cu-0.4Mn alloy was produced by squeeze casting and the heat treatment was carried out following the standard T6 treatment. It is shown that, with the addition of V, grain refinement of aluminum occurred. During heat treatment, the addition of V accelerates the precipitation kinetics of θ′ (Al2Cu) phase along the grain boundaries, and promotes the growth rate of the θ′ in the α(Al) matrix. Meanwhile, the addition of V retards the precipitation of T (Al20Cu2Mn3) phase. The tensile strength of the Al-5.0Cu-0.4Mn alloy increases with the increase of V content, which can be explained by combined effects of the solid solution strengthening and precipitate strengthening. However, excessively high V addition deteriorates the mechanical properties by forming brittle coarse intermetallic phases.

A Novel Method to Achieve Grain Refinement in Aluminum

A significant grain refinement of pure aluminum is achieved upon addition of TiCN nanoparticles (NPs). Unlike the conventional inoculation, NPs can induce the physical growth restriction through the formation of NP layer on the growing grain surface. An analytical model is developed to quantitatively account for the NP effects on grain growth. The NP-induced growth control can overcome the inherent limitations of inoculation and shed light on a potential method to achieve grain refinement.

The critical effect of Fe on the grain refinement of aluminium via Al-5Ti-1B addition

The influence of Fe on the nucleation potency of TiB2 particles was investigated by employing grain refinement of high purity aluminium in this study. Experiment results showed that without Fe, high purity aluminium cannot be refined by 0.8wt.% addition of Al-5Ti-1B. However, high purity aluminium containing 0.08wt.% Fe can be refined effectively by 0.2wt.% addition of Al-5Ti-1B, its grain size was about 206µm in diameter. Fine equiaxed grains of about 153µm in diameter can be obtained for high purity aluminium containing 0.08wt.% Fe and 0.006wt.% Ti. Grain refinement mechanism should include nucleation and dendrite remelting and multiplication. Both nucleation and dendrite remelting and multiplication played essential role on the grain refinement of aluminium. The effect of Fe was linked to increase active nuclei by segregation on TiB2 surface and then to promote nucleation of α-Al. The performance of Ti was to enhance the dendrite remelting and multiplication by forming small conglomeration zones of Ti atoms concentrated around TiB2 particles.

Relationships of diboride phases in Al–Ti(Zr)–B alloys

The relationships of diboride phases in Al–Ti(Zr)–B alloys with a variable Ti/B ratio close to the stoichiometry of TiB2 were studied. The formation of diboride solid solutions was confirmed. A grain refinement mechanism is proposed as that diboride particles in the Al–Ti–B master alloys reacting with aluminium upon adding into an aluminium melt and release titanium into the melt through forming a (Ti,Al)B2 solid solution and maintain a thin dynamic Ti rich layer on the surfaces of the (Ti,Al)B2 particles, which nucleates α-Al grains in solidification. The poisoning effect of zirconium on grain refinement of aluminium by Al–Ti–B master alloys is also discussed.

Grain refinement of Al-Mg-Sc alloy by ultrasonic treatment

In foundry practice, ultrasonic treatment has been used as an efficient technique to achieve grain refinement in aluminium and magnesium alloys. This article shows the strong effect of pouring temperature and ultrasonic treatment at various temperatures on the grain refinement of Al-1 wt% Mg-0.3 wt% Sc alloy. Without ultrasonic treatment, a fine grain structure was obtained at the pouring temperature of 700 °C. The average grain size sharply decreases from 487 ± 20 to 103 ± 2 μm when the pouring temperature decreases from 800 to 700 °C. Ultrasonic vibration proved to be a potential grain refinement technique with a wide range of pouring temperature. A microstructure with very fine and homogeneous grains was obtained by applying ultrasonic treatment to the melt at the temperature range between 700 and 740 °C, before pouring. Cavitation-enhanced heterogeneous nucleation is the mechanism proposed to explain grain refinement by ultrasound in this alloy. Moreover, ultrasonic treatment of the melt was found to lead to cast samples with hardness values similar to those obtained in samples submitted to precipitation hardening, suggesting that ultrasonic treatment can avoid carrying out heat treatment of cast parts.

On the Understanding of Aluminum Grain Refinement by Al-Ti-B Type Master Alloys

Al-Ti-B type master alloys have been widely used in the grain refinement of aluminum since 1940s. The introduction of Al3Ti and TiB2(AlB2) particles reduces the grain sizes down to about 200 micrometer level and makes aluminum alloys castable. However, the mechanism for the grain refinement is still not clear, though it is believed that TiB2 particles in the presence of Al3Ti nucleate α-Al grains during solidification. This paper presents our finding on the formation of (Ti,Al)B2 solid solution, which leads to a proposed theory on grain refinement by Al-Ti-B type master alloys that upon addition into aluminum melt stable TiB2 particles react with aluminum slowly and release titanium into the melt. The titanium thus released in combination with titanium in the melt through dissolution of Al3Ti particles maintains a dynamic titanium-rich layer on the surface of (Ti,Al)B2. This layer offers a low crystal mismatch with α-Al and promotes the nucleation of aluminum grains.

Production and Performance of Al-Ti-C Grain Refiners with Addition of K2TiF6 and Elemental Carbon

Abstract AlTiC master alloys were improved greatly and used as a new type in grain refinement of aluminum and aluminum alloys. In the present work, Al-Ti-C grain refiners with different Ti/C ratios were in-situ produced by the addition of K2TiF6 and elemental carbon powder mixture to the commercial pure aluminum. The effects of casting temperature and Ti/C ratio on the grain refinement process were investigated by the so-called Alcoa Cold Finger test and respective optimum conditions were determined. The results indicate that the produced Al-Ti-C master alloys contain TiC and TiAl3 particles within the aluminum matrix. The proper conditions for evaluating the efficiency of the produced Al-Ti-C master alloy to obtain a minimum grain size are: Temperature of 1300 °C, holding time of 20 minutes, and a Ti/C 0.60 wt.-%

Microstructural Evolution and Grain Refining Efficiency of Al-10Ti Master Alloy Improved by Copper Mold Die Casting

The microstructural evolution and grain refining efficiency of sub-rapidly solidified (SRS) Al-10Ti master alloy has been studied. The results show that the mean size of Al3Ti particles in the SRS Al-10Ti master alloy decreased significantly and the morphology changed from strip-like to blocky and short rod-like compared with the conventional Al-10Ti master alloy. Grain refining experiments show that the SRS Al-10Ti master alloy is more effective than the conventional master alloy for refining Al-7Si alloy. The conversion rate of columnar to fine equiaxed grain structure in the Al-7Si alloy was promoted by the addition of SRS master alloy, and the microhardness of Al-7Si alloy increased. The mechanisms of grain refinement of aluminum by inoculation with improved Al-10Ti master alloy are discussed based on the solute theory. The decrease in size, increase in quantity, and change in morphology of Al3Ti particles are considered as the reasons for the improvement of microstructure and microhardness.

Microstructure characteristic and grain refining performance of Al–5Ti–1B master alloy improved by copper mould die casting

The influence of subrapid solidified processing parameters on the microstructure characteristic and grain refining efficiency of Al–5Ti–1B master alloy has been studied. The results show that the mean size of Al3Ti particles in Al–5Ti–1B master alloy decreases significantly after copper mould die casting. The morphology of Al3Ti particles changed from plate-like to blocky and petaloid. Compared with conventional Al–5Ti–1B master alloy, the phase constitution of subrapidly solidified Al–5Ti–1B master alloy does not change, and the improved master alloy shows a better grain refining efficiency. The microhardness of the pure aluminium refined by conventional and improved Al–5Tu–1B obeys the Hall–Petch relation, and the material constant kH is in the range of 84·02–91·80 MPa μm1/2. The mechanisms of grain refinement of aluminium by inoculation with improved Al–5Ti–1B master alloy are discussed based on the duplex nucleation theory and growth restriction effects in aluminium alloys.

Effect of Zirconium Addition on the Grain Size and Mechanical Behavior of Aluminum Grain Refined by Titanium Plus Boron (Ti+B) in the as Cast and Cold Extruded Conditions

Aluminum and its alloys are the second most commonly used metal for a variety of industrial applications. They normally solidify in coarse grain columnar structure which tends to reduce their mechanical behavior and surface quality. It was found that this large grain size structure can be refined by using titanium, Ti, or titanium plus boron, Ti+B, and using the latter resulted in reducing the amount of Ti to fifth its values although boron itself is not a grain refiner. This is why it is becoming customary in the aluminum foundry to add Ti or Ti+B to their melt before solidification. The available literature reveals that most of the work is directed towards the metallurgical aspects and little was directed on the mechanical aspects. To the best of the authors knowledge, no work was directed on the aspects of grain refiners on the formability of metals. In this paper, the effect of addition of Zr on the mechanical properties of commercially pure aluminum grain refined by Ti+B in the as cast and extruded conditions is investigated. Comparison between the addition of Zr alone or Zr+Ti+B is also investigated. It was found that addition of Ti+B either alone or in the presence of Zr resulted in grain refinement of aluminum both in the as cast and in the cold extruded conditions. The maximum reduction in grain size was 53.22% and 76.92%, respectively. Similarly, it was found that addition of Ti+B either alone or in the presence of Zr to Al resulted in improvement of its Vickers's hardness, However addition of Zr alone to Al resulted in decrease of its hardness in the as cast conditions but increase in the extruded condition .The maximum increase was in the case of adding both of them in the extruded condition being 94.59 %, (from Hv 37 to Hv72). Similarly the ultimate tensile strength, UTS, was improved at all additions except when Ti+B or Zr is added alone. On the whole it may be concluded that addition of Zr to Al grain refined by Ti+B resulted in enhancement of its grain size and improvement of its hardness, mechanical strength and ductility in the cold extruded conditions and resulted in slight decrease of its ductility when added in the as cast condition.

Grain refinement of pure aluminium and Al–7Si with Al–3B master alloy

The potential of AlB2 particles in the grain refinement of aluminium alloys with and without Si was investigated in an effort to develop potent grain refiners for Al–Si based foundry alloys. The Al–Si alloys are grain refined with the Al–3B alloy, whereas pure aluminium is not. The cast grain size in the former decreases with increasing Si content. The addition of 200 ppm B into the Al–7Si alloy, the basis of most commercial foundry alloys, produces remarkably fine grains with no fading effect. The Al–B system relies on a eutectic reaction L→α (Al)+AlB2 at 659·7°C to offer grain refinement, which occurs predominantly via heterogeneous nucleation of α (Al) grains on AlB2 particles thus made available. The grain refinement starts at a critical Si content enough to depress the liquidus temperature of the alloy sufficiently below the eutectic reaction temperature. The grain refining efficiency improves with increasing Si content owing to a decreasing liquidus temperature, which in turn facilitates the formation of an increasing number of solid nuclei. Alloys with insufficient level of Si to displace the liquidus temperature of the alloy below the eutectic reaction temperature cannot take advantage of this reaction and thus enjoy grain refinement. This is clearly why pure aluminium with a liquidus point above the eutectic reaction temperature is not grain refined with the Al–3B alloy at all.