Effect Of Solidification Rate Research Articles

3D X-ray Tomography Analysis of Mg–Si–Zn Alloys for Biomedical Applications: Elucidating the Morphology of the MgZn Phase

Temporary metal implants, made from materials like titanium (Ti) or stainless steel, can cause metabolic issues, raise toxicity levels within the body, and negatively impact the patient’s long-term health. This necessitates a subsequent operation to extract these implants once the healing process is complete or when they are outgrown by the patient. In contrast, medical devices fabricated from absorbable alloys have the advantage of being biodegradable, allowing them to be naturally absorbed by the body once they have fulfilled their role in facilitating tissue healing. Among the various absorbable alloy systems studied, magnesium (Mg) alloys stand out due to their biocompatibility, mechanical properties, and corrosion behavior. The existing literature on absorbable Mg alloys highlights the effectiveness of silicon (Si) and zinc (Zn) additions in improving mechanical properties and controlling corrosion susceptibility; however, there is a lack of comprehensive quantitative morphological analysis of the intermetallic phases within these alloy systems. The quantification of the complex morphology of intermetallic particles is a challenging task and has significant implications for the micromechanical properties of the alloys. This study, therefore, aims to introduce a robust set of morphometric parameters for evaluating the morphology of intermetallic phases within two as-cast Mg alloys with Si and Zn additions. X-ray Computed Tomography (XCT) was used to capture the 3D tomographic data of the alloys, and a novel pair of morphological parameters (ratio of convex hull to particle volume and convex hull sphericity) was applied to the 3D tomographic data to assess the MgZn phase formed in the two alloys. In addition to the impact of composition, the effect of solidification rate on the morphological parameters was also studied. Furthermore, Scanning Electron Microscopy (SEM) and Energy-Dispersive Spectroscopy (EDS) were employed to gather detailed 2D microstructural and compositional information on the intermetallics. The comprehensive characterization reveals that the morphological complexity and size distribution of the MgZn phase are influenced by both compositional changes and the solidification rate. However, the change in MgZn intermetallic particle morphology with size was found to follow a predictable trend, which was relatively agnostic of the chosen casting conditions.

A high-strength Al-Cu-Sc alloy fabricated by rapid solidification and direct aging

The effect of solidification rates and heat treatment on the microstructure and mechanical properties of Al-Cu-Sc alloys was investigated. The results demonstrate that rapid solidification (RS) effectively prevents the formation of the W phase, which is common in conventional solidification (CS) alloys. Additionally, the supersaturated Cu solute within the RS matrix facilitates direct aging, leading to uniform and fine θ′ precipitates. Although the number density of θ′ is slightly lower than in the CS Al-Cu + T6 alloy, the dense Al3Sc nanodispersoids compensate for the strength loss in another aspect. As expected, the RS Al-Cu-Sc + aging alloy exhibits superior tensile strengths and ductility. The improvement in strength can be primarily attributed to Orowan strenthening and precipitation strengthening, related to Al3Sc nanodispersoids and θ′ precipitates.

Investigation of the formation mechanism between β-NiAl and C14-Laves phases in laser additive manufacturing of nickel-based superalloy

The microstructure of laser additively manufactured nickel-based superalloy was analyzed using multi-scale characterization. The phase composition of the as-deposited sample was determined. The formation mechanisms of β-NiAl and C14-Laves phases were studied in depth. The crystallographic orientation relationship between the β-NiAl and C14-Laves phases was elucidated. The formation of the β-NiAl phase exacerbates the elemental segregation at the interface, leading to the generation of micro-strain and dislocations that provide nucleation sites for the C14-Laves phase. In addition, the effect of solidification rate on the precipitation of precipitated phases from the alloy was excluded. The present work contributes to understanding the precipitation behavior of β-NiAl and C14-Laves phases in nickel-based superalloys.

Strength and ductility dual-enhancement of Ni36Co30Fe11Cr11Al6Ti5Nb1 high entropy alloy by directional solidification

Ni36Co30Fe11Cr11Al6Ti5Nb1 high entropy alloys (HEAs) were prepared by directional solidification. The effect of solidification rate on microstructure evolution and mechanical properties was systematically investigated. Results show that the microstructure has a dendritic morphology with uniform orientation. FCC phase rich in Co, Cr and Ni is formed in the dendrite. Laves phase rich in Nb and Ti and FCC phase rich in Ni and Ti are formed between dendrites. With the increase of solidification rate, the dendrites are gradually refined. Tensile results show that the yield strength and elongation increase with the increase of solidification rate. The yield strength and elongation at 100 μm/s are 606.2 MPa and 27.6 %, respectively, achieving an excellent combination of strength and plasticity. Fine-grain strengthening, second-phase strengthening and solid-solution strengthening are the dominant strengthening mechanisms. The dendrites growing along the directional direction reduce the transverse grain boundaries and avoid the rapid propagation of cracks.

The influence of cooling rate on microstructure and magnetic properties of cast Fe-6.5wt%Si steel

Fe-6.5wt%Si steel samples of different thicknesses (1 mm, 2 mm, and 5 mm) were prepared by arc-melting and suction-casting with sub-rapid solidification rates. The microstructures and magnetic properties of the samples were studied, and the effect of solidification rates were discussed. Results show that columnar crystals are generated with a <100> fiber texture after casting. Ordered phases B2 and D03 are inhibited by sub-rapid solidification, and such an effect is clear in the 1 mm thick sample with the largest cooling rate. With decreasing cooling rate, the grain size increases, with the mean values being 66.6±30.8 μm, 93.0±42.8 μm, and 149.7±66.8 μm, and the intensity of the <100> texture increases, with the values being 3.14 mrd, 3.56 mrd, and 5.85 mrd, respectively. The 5 mm thick sample with the lowest cooling rate exhibits the best magnetic properties (B8=1.30 T, B50=1.55 T, P1/50=2.19 W/kg, P1/400=37.85 W/kg).

Effect of solidification rate on dendrite segregation and mechanical properties of Cu–15Ni–8Sn alloy prepared by directional solidification

Effect of solidification rate on dendrite segregation and mechanical properties of Cu–15Ni–8Sn alloy prepared by directional solidification

Effect of Solidification Rate on Microstructure and Mechanical Characteristic of Gray Cast Iron

Effect of Solidification Rate on Microstructure and Mechanical Characteristic of Gray Cast Iron

Effects of solidification rate and heat treatment on microstructure characterization and hot tensile strength of single crystal CMSX-4 superalloy

Single crystal CMSX-4 Ni-based superalloy, consisting of rhenium and hafnium elements, were directionally solidified at three different withdrawal rates of 2, 3, and 4 mm/min through a Bridgman furnace. After that a full solution heat treatment was followed by two step aging at 1140 °C/6 h and 870 °C/20 h respectively. Microstructural characteristics, e.g. the primary and secondary dendrite arm spacing, the size and volume fraction of γ ́ phase, and percentage of porosity were analyzed using the optical microscopy (OM) and scanning electron microscopy (SEM) equipped with an energy dispersive spectroscopy (EDS) detector. It was found that an increase in the withdrawal rate of the as-cast specimens led to a reduction in the values of primary and secondary dendrite arm spacing, the percentage of porosity and also size of γ ́. In addition, at higher withdrawal rates, the γ/γ ́ eutectic phase is distributed from a continuous and blocky shaped to fine scattered islands. Nevertheless, the minimum volume fraction of eutectic was obtained at the withdrawal rate of 3 mm/min. Heat-treatment of the specimens associated with formation of a noticeable cuboidal γ’-precipitates, which was about 70% at withdrawal rate of 3 mm/min. Furthermore, the aged specimens indicated the lower γ/γ ́ eutectic phase compared to as-cast specimens, while the percentage of porosity increased for aged specimens. Eventually, the highest ultimate tensile strength of the single crystal CMSX-4 at 870 °C was measured to be 1170 MPa which was obtained at a withdrawal rate of 3 mm/min, due to the high volume fraction of the γ ́ phase and the lower values of γ/γ ́ eutectic phase.

The Effect of Solidification Rate on the Corrosion Resistance of Die-Cast AZ91 Magnesium Alloy.

To increase the utilization of die-cast Mg alloys with various shapes in a variety of environments, the corrosion behaviors of commercial die-cast Mg alloys with different thicknesses were investigated in neutral and alkali solutions at ambient temperature. A decrease in the thickness of a specimen leads to an increase in cooling and solidification rates, which, in turn, decreases the size of the eutectic β phases and the interphase distance, thus improving the hardness of the specimen. Specimens with relatively large β phases were more corroded under neutral conditions due to severe galvanic corrosion at the interface between α-Mg and the β phases, whereas they were protected by passivation films formed on the substrate in the alkaline solution. However, in the case of the alloy with thin thickness and high solidification rate, the fine β phases improved corrosion resistance by forming a net structure that acted as a barrier to corrosion propagation of the α matrix. These results suggest that the size and distribution of the eutectic phases should be appropriately controlled, depending on the environment.

Effect of Solidification Rates at Sand Casting on the Mechanical Joinability of a Cast Aluminium Alloy

Implementing the concept of mixed construction in modern automotive engineering requires the joining of sheet metal or extruded profiles with cast components made from different materials. As weight reduction is desired, these cast components are usually made from high-strength aluminium alloys of the Al-Si (Mn, Mg) system, which have limited weldability. The mechanical joinability of the cast components depends on their ductility, which is influenced by the microstructure. High-strength cast aluminium alloys have relatively low ductility, which leads to cracking of the joints. This limits the range of applications for cast aluminium alloys. In this study, an aluminium alloy of the Al-Si system AlSi9 is used to investigate relationships between solidification conditions during the sand casting process, microstructure, mechanical properties, and joinability. The demonstrator is a stepped plate with a minimum thickness of 2.0 mm and a maximum thickness of 4.0 mm, whereas the thickness difference between neighbour steps amounts to 0.5 mm. During casting trials, the solidification rates for different plate steps were measured. The microscopic investigations reveal a correlation between solidification rates and microstructure parameters such as secondary dendrite arm spacing. Furthermore, mechanical properties and the mechanical joinability are investigated.

The Effect of Solidification Rate on the Microstructure and Mechanical Properties of Pure Magnesium

Magnesium, Mg, has been widely investigated due to its promising potential as magnesium alloys for various applications, particularly as biomedical implantation devices among other medical applications. This work investigates the influence of different cooling rates on the strength of pure Mg. The cooling rates were set to cover a low cooling rate LCR (0.035 °C/s) in an insulated furnace, a moderate cooling rate MCR (0.074 °C/s) in uninsulated-ends furnace, and a high cooling rate HCR (13.5 °C/s) in liquid CO2. The casting process was accomplished using a closed system of melting and cooling due to the reactivity-flammability of magnesium in order to minimize processing defects and increase the safety factor. The as-cast samples were metallographically examined for their microstructure, and properties such as impact strength, hardness, and tension were determined. Increasing the solidification rate from 0.035 °C/s to 0.074 °C/s increased the hardness from 30 to 34 Rockwell Hardness and the UTS from 48 to 67 MPa. A higher solidification rate of 13.5 °C/s further enhanced the hardness to 48 Rockwell Hardness and the UTS to 87 MPa in comparison to the 0.074 °C/s cooling rate. Additionally, the fracture behavior and morphology were investigated. It was found that in general, the mechanical properties tended to improve by refining the grain structure.

Segregation Phenomenon of As-Cast and Heat Treatment Microstructures in Investment Casting of IN738LC Superalloy

The effect of solidification rate on micro-segregation in investment casting of IN738LC superalloy was studied. In Ni-based superalloys, the micro-segregation of solute atoms is formed due to limited diffusion during cast and solidification. The microstructure of cast Ni-based superalloys is largely divided into dendrite core of initial solidification and interdendrite of final solidification. In particular, mosaic shaped eutectic γ/γ’ and carbides are formed in the interdendrite of the final solidification region in some cases. The micro-segregation phenomena formed in regions of dendrite core and interdendrite including eutectic γ/γ’ and carbides were analyzed using OM, SEM/EDS and micro Vickers hardness. As a result of analysis, the lack of (Cr, W) and the accumulation of Ti were measured in the eutectic γ/γ’, and the accumulation of (Cr, Mo) and the lack of Ti were measured in the interdendrite between dendrite and eutectic. Carbides formed in interdendritic region were composed of (Ti, W, Mo, C). The segregation applied to each microstructure is mainly due to the formation of γ’ with Ni3(Al,Ti) composition. The Ni accumulation accompanied by Cr depletion, and the Ti accumulated in the eutectic region as a γ’ forming elements. The Mo tends to diffuse out from the dendrite core to the interdendrite, and the W diffuse out from the interdendrite to the dendrite core. Therefore, the accumulation of Mo in the interdendrite and the deficiency of W occur in the eutectic region located in the interdendrite. Heat treatment makes the degree of the micro-segregation decrease due to the diffusion during solid solution. This study could be applied to the heat treatment technology for the micro-segregation control in cast Ni-based superalloys.

Effects of solidification rate on the leaching behavior of metallic impurities in metallurgical grade silicon

Precipitation of the impurity phase during the solidification of metallurgical grade silicon melt determines the distribution law and occurrence state of impurities in silicon, while also determining the removal efficiency of impurities during the leaching process. In this research, distribution and occurrence states of inclusions in silicon at different solidification rates were detected via an electron probe microanalyzer (EPMA). Results have shown that the size of the inclusions becomes larger following electric resistance remelting, and some new impurity phases are generated, such as the VSi2 phase, TiSi2 phase, Si-Fe-Al-Ni-Zr phase, and Si25FeAl2Ca16NiCu2 phase. It is seen that there are clear boundaries between different phases. In addition, based on agitation leaching of 4.0 mol·L−1 HCl and 2.0 mol·L−1 HF mixed acid, it was found that most of the impurities in industrial silicon were effectively removed during this process. The impurities in the industrial silicon decreased from 5233.0 ppmw to 181.7 ppmw. The precipitation of the Si-Fe-Al-Ni-Zr (Cu) phase was the main factor providing improved efficiency of impurity removal, which exposed the impurity elements to the greatest extent. Industrial silicon was subjected to resistance remelting at different solidification rates, and the removal effects of impurities were also different. The impurity removal effect was optimal at a solidification rate of 1 °C/min, as the impurities were reduced to 131.9 ppmw.

Effect of solidification rate and Al content on solid solution in Mg–Al–Zn alloy

Mg–Al–Zn alloys with different Al content and different cooling conditions were prepared. The solid solution content of Al and Zn in the alloy was determined by electrochemical phase separation. The results show that Al has a large amount of solid solution, while Zn has a very low amount. Al can play a role in solid solution strengthening, while Zn is very small. Al has a repulsive effect on Zn and reduces the solid solubility of Zn. The higher the Al content it has, the larger the Al solid solution and the smaller the Zn solid solution we observe. The higher the solidification cooling rate is, the greater the solid solution amount of Al and Zn is.

Investigation of the effect of solidification rate on microstructure of Al-0.13Si-0.3Fe DC-cast alloy using EBSD and DSC techniques

Abstract Direct chill (DC) casting is used to cast aluminum alloy ingots. Casting speed influences the distribution and types of iron intermetallics in aluminum ingot microstructure. This study attempted to identify and quantify the iron intermetallic phases in the microstructure of laboratory scale DC Al- 0.13Si-0.3Fe samples using differential scanning calorimetry, scanning electron microscopy, electron backscatter diffraction, and energy dispersive X-ray spectroscopy. Both stable and non-stable iron intermetallic phases were observed but to different extents in all alloy samples’ microstructure. Two different types of iron-rich, AlFeSi globular particles were observed in the alloy samples’ microstructure. As a result, an attempt was made to understand the formation temperature and composition of these small, globular particles. DSC results confirmed that the enthalpy change of phase formation is dependent mainly on the volume fraction of the iron intermetallic phase in the microstructure. A good agreement was observed between the quantitative analysis results and the DSC analysis, which supports the reliability of the quantitative methods used in this study. The results obtained in this study bridge existing gaps in literature on the effect of cooling rate on the selection of iron intermetallic phases, in general, and in the AlSiFe globular particles, in particular.

Solidification rate driven microstructural stability and its effect on the creep property of a polycrystalline nickel-based superalloy K465

Different solidification rates may cause a significant difference in microstructure and creep property in different locations of turbine blades in aircraft engines. In this study, the effect of solidification rate on microstructural stability and creep property was revealed in a polycrystalline nickel-based superalloy K465. The K465 alloy was cast as a turbine blade, solid bars and hollow tubes. A larger cross section size caused a slower solidification rate in the blade shank and bar than that of the blade airfoil and tube. Microstructural characteristics and corresponding stress rupture properties under 975 °C/225 MPa were investigated after thermal exposure at 900 °C for 300–1000 h. Plate-like μ phase formed only in the interdendritic regions of the blade shank and the bar, but not in the blade airfoil and the tube after thermal exposure. The precipitation of μ phase was mainly responsible for the much worse stress rupture property of the bar in comparison with the tube. The microsegregation degree, chemical composition of γ matrix and precipitates including γ′ phase and various carbides, and dislocation configurations were examined. Compared to the tube, a slower solidification rate caused a higher degree of microsegregation, coarser γ′ precipitates and carbides, as well as a much higher dislocation density in the bar after standard solution treatment. The formation of μ phase was stress-induced and attributed to the remaining dislocations in the interdendritic regions. A longer solution treatment was suggested to effectively suppress the formation of μ phase in the bar and blade shank for practical applications. These results provide a guidance for the manufacturing and evaluation of microstructural degradation of turbine blades made from conventionally cast polycrystalline nickel-based superalloys.

Effects of Solidification Rate on Microstructure and Mechanical Properties with Sb at Different Ratio of AZ91 Quality Mg Alloy

Mevcut kullanim alanlari gun gectikce artis gosteren Mg alasimlarinin, teknolojik gelismelere uyum saglayabilmesi icin mekanik ozellikler bakimindan daha fazla gelistirilmesi gerekliligi ortaya cikmistir. Gunumuzde cozunebilir biyo-malzeme olarak saglik alaninda da kullanilmaya baslayan Mg ve alasimlarina kazandirilan fiziksel ve mekanik ozellikler malzemenin kullanim omrunu tayin etmektedir. Dolayisiyla bu calismada, AZ91 serisi Mg alasimina farkli oranlarda (%0.2 - %0.5 ve %1.0) Sb elementi ilavesi ve katilasma hizinin da etkisiyle mekanik ozelliklerinin gelistirilmesi amaclanmistir. Yapilan calismanin neticesinde sonuclar incelendiginde; AZ91 alasiminin genel olarak tane yapisinin α-Mg ve tane sinirlari boyunca yayilan β-Mg 17 Al 12 fazindan olustugu saptanmistir. Hizli sogumanin tane yapisinda kuculmelere sebep oldugu bununla birlikte tane sinirlarinda bulunan Mg 17 Al 12 intermetalik fazinin incelip parcalandigi tespit edilmistir. Tespit edilen bu etkilerin neticesinde de alasimin cekme, akma ve uzama degerlerinde a rtisin oldugu gozlenmistir. Bununla birlikte AZ91 alasimina ilave edilen Sb ile yapida Mg 3 Sb 2 fazi olusmustur. Bu intermetalik fazin yapida meydana getirdigi degisiklikler ile alasimin mekanik ozelliklerinde artis izlenmistir. AZ91 alasiminin cekme dayanimi Sb ilavesi ile 163 MPa seviyelerinden 217 MPa seviyelerine kadar iyilesmistir. Sb ilavesiyle AZ91 alasiminda sertlik degerleri yaklasik 57 HV degerlerinden 81 HV degerlerine yukselmistir.

Effect of Solidification Rate on the Microstructure and Strain-Rate-Sensitive Mechanical Behavior of AlCoCrFeNi High-Entropy Alloy Prepared by Bridgman Solidification

Effect of Solidification Rate on the Microstructure and Strain-Rate-Sensitive Mechanical Behavior of AlCoCrFeNi High-Entropy Alloy Prepared by Bridgman Solidification

Effect of solidification rate on microstructure and toughness of Ca-Ti modified high boron high speed steel

In this work, the effect of solidification rate on the microstructure and impact toughness of high boron high speed steel is systematically investigated. The theoretical and experimental results indicate that the as-cast microstructure of high boron high speed steel consists of α-Fe matrix and eutectic borocarbide. Without Ca-Ti addition, borocarbide presents a continuous and reticular structure. After Ca-Ti modification, borocarbide possesses an isolated, fine structure. Besides, cooling rate obviously affects the extent of spheroidization. In modified high boron high speed steel, calcium possesses surface activity, which restrains the growth of eutectic borocarbide during solidification. Titanium exists in the form of dispersedly distributed TiC particles which act as heterogeneous nuclei for eutectic borocarbide. The impact toughness of high boron high speed steel is remarkably improved by Ca-Ti modification, which can be further improved by cooling rate. The effect of cooling rate on improving of the toughness can provide a scientific basis for the foundry process designing.

Prediction of crack tip plasticity induced due to variation in solidification rate of weld pool and its effect on fatigue crack propagation rate (FCPR)

Effect of solidification rate on crack tip plastic zone size at various crack lengths was calculated analytically and numerically by simplified Sih’s and Irwin’s models, respectively. Influence of plastic zone size is explained in terms of COD and elastic stress intensity factor within valid range of small scale yielding approximation. Up to plastic zone size range of 4–5 mm, a good agreement between numerical and analytical plastic zone size and elastic stress intensity factor for all weldments was observed. For high loads and greater crack lengths, experimentally obtained COD values were found 15–19 % more than simulation ones due to rapidly induced plasticity at high crack dimensions. Solidification rate showed a significant influence on FCPR, for solidification rates 13.75 °C/s, 6.97 °C/s and 4.32 °C/s the obtained fatigue strength was 35.29 MPa, 36.26 MPa and 41.32 MPa, respectively.