Influence Of Rapid Solidification Research Articles

The Influence of Rapid Solidification on Corrosion Behavior of Mg60Zn20Yb15.7Ca2.6Sr1.7 Alloy for Medical Applications.

Biodegradable magnesium alloys with Zn, Yb, Ca and Sr additions are potential materials with increased corrosion resistance in physiological fluids that ensure a controlled resorption process in the human body. This article presents the influence of the use of a high cooling rate on the corrosion behavior of Mg60Zn20Yb15.7Ca2.6Sr1.7 alloy proposed for medical applications. The microstructure of the alloy in a form of high-pressure die-casted plates was presented using scanning electron microscopy in the backscattered electrons (BSEs) mode with energy-dispersive X-ray spectrometer (EDX) qualitative analysis of chemical composition. The crystallization mechanism and thermal properties were described on the basis of differential scanning calorimetry (DSC) results. The corrosion behavior of Mg60Zn20Yb15.7Ca2.6Sr1.7 alloy was analyzed by electrochemical studies with open circuit potential (EOCP) measurements and polarization tests. Moreover, light microscopy and X-ray photoelectron spectroscopy were used to characterize the corrosion products formed on the surface of studied samples. On the basis of the results, the influence of the cooling rate on the improvement in the corrosion resistance was proved. The presented studies are novel and important from the point of view of the impact of the technology of biodegradable materials on corrosion products that come into direct contact with the tissue environment.

Influence of Rapid Solidification and Optimized Process Parameters on the Microstructural Evolution of Additive Manufactured Titanium Alloy Grade 5 Composite

The study experimentally investigates the effects that Ytterbium Laser System process parameters, such as laser power, powder feed rate and traverse speed, has on the resultant microstructure of Ti- 6Al-4V grade 5 alloy. The deposition process was conducted employing a 3kW (CW) Ytterbium Laser System (YLS-2000-TR) machine, coaxial to the reinforcement powder. The laser scanning speed and power were varied between the intervals of 1-1.2 m/min and 900-1000 W. All other parameters kept constant where the rate of gas flow, the spot diameter, and the rate of powder flow. The microstructure was characterized by grain size and morphology by using Optical Microscopy (OM) and Scanning Electron Microscopy (SEM). The microstructural and mechanical properties were ascertained and the relationships with the process parameters were achieved. As a result of rapid cooling, the morphological features of α and α’ are distinctive and appear acicular. The structures appear coarsened. The metallurgy of the samples identifies with a morphology of multi-scale; with the coarsened alpha structures being reduced, plate-like, discrete and finer. The alpha grains closer to the fusion zone grew epitaxially, and the ones above these are acicular and lamellar. The results also indicated that slow traverse speeds increase the scale of columnar grains, while other process parameters were kept constant. Columnar microstructures became prevalent due to the dynamic temperature gradients/spikes, and sustainable cooling rates, pertaining to fabricating direct laser deposited Ti-6Al-4V grade 5 alloy. It was ascertained that by increasing the traverse speeds, the cooling rates increased, which resulted in a decrease in the width of the columnar grains.

Formation and wear property of broad-beam laser clad Fe-based coatings

Broad-beam laser cladding (BLC) is an efficient method for coating preparation with wide application. However, the fabrication of advanced alloys by BLC has been rarely reported. The coating quality, microstructure and wear performance of the FeBSiNb coatings prepared by BLC were investigated in this paper. The coating quality and wear property of the Fe-based coatings were effectively improved by optimizing process parameters. Under the influence of rapid solidification by BLC, the FeBSiNb coatings exhibited a composite phase structure consisting of a major component of intragranular α-Fe phase and intergranular Fe2B phase. The in-situ generation of Nb-B particles dispersed all over the coatings, not only enhancing the mechanical property, but significantly increasing the wear resistance. The different cracking characteristics and heterogeneous segregation strengthening mechanism of FeBSiNb coatings have also been discussed for elucidating the progressive coating quality and excellent wear resistance, respectively.

Influence of rapid solidification on mangnetostructural and magnetocaloric effect in Ni53Mn24Ga23 alloy

The present investigation is focused on the structural transformation, microstructure and magnetocaloric effect (MCE) of Ni53Mn24Ga23 alloy in the form of melt spun ribbons prepared by rapid solidification technique. The properties have been compared with bulk alloy prepared by conventional melting-casting route. The rapidly solidified alloys revealed higher magnetic entropy change (−8.5 J.Kg−1K−1) compared to that of bulk (−7.7 J.Kg−1K−1). The high magnetic entropy change and low thermal hysteresis are correlated to different magnetostructural behaviour.

Iron in solution with aluminum matrix after non-equilibrium processing: an atom probe tomography study

In this paper, we report on the influence of rapid solidification and severe plastic deformation on the solid solubility of Fe in Al. Atom probe tomography, for the first time, was performed on fine (3–4 μm diameter) and coarse (~100 μm) as-atomised Al-5 at.% Fe powder and cryomilled Al-5 at.% Fe powder. The atomised powders exhibited negligible Fe in solution with Al, whereas the cryomilled powder contained ~2 at.% Fe in solution. Moreover, our results suggest that severe plastic deformation is preferable to atomisation/rapid solidification for increasing the non-equilibrium solid solubility of Fe in Al.

Influence of rapid solidification on Sn–8Zn–3Bi alloy characteristics and microstructural evolution of solder/Cu joints during elevated temperature aging

The effects of rapid solidification on the microstructure and melting behavior of the Sn–8Zn–3Bi alloy were studied. The evolution of the microstructural characteristics of the solder/Cu joint after an isothermal aging at 150 °C was also analyzed to evaluate the interconnect reliability. Results showed that the Bi in Sn–8Zn–3Bi solder alloy completely dissolved in the Sn matrix with a dendritic structure after rapid solidification. Compared with as-solidified Sn–8Zn–3Bi solder alloy, the melting temperature of the rapid solidified alloy rose to close to that of the Sn–Zn eutectic alloy due to the extreme dissolution of Bi in Sn matrix. Meanwhile, the adverse effect on melting behavior due to Bi addition was decreased significantly. The interfacial intermetallic compound (IMC) layer of the solder/Cu joint was more compact and uniform. Rapid solidification process obviously depressed the formation and growth of the interfacial IMC during the high-temperature aging and improved the high-temperature stability of the Sn–8Zn–3Bi solder/Cu joint.

Influence of rapid solidification and lithium additions on microstructure and mechanical properties of aluminum based alloys

A series of aluminum-lithium or lightweight alloys containing up to 5 wt. % lithium was rapidly solidified from melt by chillblockmelt-spun technique. The resultant ribbons were studied by X-ray diffraction (XRD), scanning electron microscope(SEM) and deferential scanning calorimetry (DSC) techniques. The results showed that the structures of all melt-spunribbons were completely composed of two distinct phases’ aluminum rich phase and intermetallic compound (IMC) Al9.8-Li1.1phase. It is also found that melting point, solidus and liquidus temperatures of the lightweight alloys are lowered asthe Li content is increased. Additionally, elastic moduli, internal friction, thermal diffusivity and hardness measurements ofmelt-spun ribbons were examined by using dynamic resonance method and Vickers indenter for one applied load of 25grams of force for 5, 20, 40, 60, 80 and 99 seconds. Results interpreted in terms of the phase changes occurring in thealloy system. With the addition of Li, the Al rich phase is finer in grain size, and intermetallic compound is more uniformlydistributed. As a result, Young's modulus and micro-hardness of Lightweight are increased when Li is added into the Alalloy. The aim of the research planned in this work was to design the A1-Li family of alloys contribute to their increasinglybroad application in aeronautics, as an alternative for the aluminum alloys, which have been used so far.

The influence of rapid solidification on the microstructure of the 17Cr–9Ni–3Mo precipitation hardened steel

The 17Cr–9Ni–3Mo precipitation hardened (PH) steel was processed after re-melting using different cooling rates including copper plate chilling and the melt-spinning. The effect of different cooling rates and the sub-zero treatment on the microstructure of the 17Cr–9Ni–3Mo steel was studied. The microstructure and the phase composition of the steel was investigated using light microscopy (LM), scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS), transmission electron microscopy (TEM), the X-ray diffraction (XRD) and Mössbauer spectroscopy. The results show that the microstructure of 17Cr–9Ni–3Mo steel after rapid solidification consists of austenite and δ-ferrite. The quantity of austenite increases with the increase of cooling rate. Sub-zero treatment of the samples cooled at the rate of 4×104K/s and 2×105K/s reduces the quantity of austenite as a result of austenite → martensite transformation. For the samples cooled at the rate of 2×106K/s the quantity of austenite in the microstructure does not change when compared to the state before and after sub-zero treatment. The model for the formation of microstructures during rapid cooling was proposed.

Influence of the Reprocessing by Plasma Melting and Injection Molding on the Thermomechanical Properties of a Ni-Ti SMA Manufactured by VIM

ABSTRACTShape Memory Alloys (SMA) metallic materials that change their mechanical and physical properties with temperature variation and mechanical loading, surprising engineers and researchers. In this way, one can develop thermomechanical actuators capable, for example, of generating force by blocking the shape recovery or change the natural frequency of a mechanical system by blocking resonance. The processing of these SMA are countless, each one with its specific limitation and particularity. This study aims to evaluate the influence of rapid solidification of a Ni-Ti SMA that is originally manufactured by Vacuum Induction Melting (VIM) and reprocessed by Plasma Melting (PM) followed by injection molding into different metal molds (steel, brass, aluminum and copper). The influence of such a processing is analyzed through Differential Scanning Calorimetry (DSC) and Electrical Resistance as a function of Temperature (ERT) to determine the effects on transformation temperatures. The results demonstrate that by using the copper mold one can provide greater uniformity of the material properties. Thus, there is the possibility of obtaining different kinds of SMA mini-actuators by PM injection in a copper mold and that includes different shapes and sizes that can be studied further.

Influence of rapid solidification on microstructure, thermodynamic characteristic and the mechanical properties of solder/Cu joints of Sn–9Zn alloy

Rapidly solidified Sn–9Zn alloy foils were prepared by the melt-spinning method. The effects of rapid solidification process on the microstructure, thermodynamic characteristic, electrochemical corrosion properties and spreading properties of Sn–9Zn solder alloys were analyzed. The mechanical properties and fracture behaviors of the solder/Cu joints were also investigated. The results showed that the rapid solidification process could obviously refine the solidification structure of Sn–9Zn alloy and a fine netlike dendrite structure was formed due to the rapid branch of Sn phase. The Zn phase was distributed in Sn matrix in granular form. After rapid solidification, the pasty range decreased from 7K to 4K, the wettability was modestly improved, and the corrosion resistance of the rapid solidified alloy was improved significantly. The tensile shear strengths of the joints using the rapidly solidified solder were obviously higher than that of the joints using the as-solidified solders result from the formation of fine-grained intermetallic compound (IMC) with a needle pattern and more uniform IMC layer at the interface.

Microstructure and Mechanical Properties of Rapidly Solidified Al-Fe-Ni-Mg Alloys

Rapid solidification (RS) combined with following mechanical consolidation of RS powders is considered as a valuable commercial method for the production of a wide range of metallic materials having fine-grained structures. Reported research results for various alloys demonstrate better compositional homogeneity, smaller grain size and relatively fine precipitates distributed homogenously in RS alloys than that for the materials produced by conventional metallurgical processing. The effect of rapid solidification on the microstructure and mechanical properties of selected Al-Fe-Ni-Mg alloys have been investigated. The basic item of the research work was obtaining aluminum PM materials strengthened by highly-dispersed transition metal compounds and aluminum-magnesium solid solution. Rapid solidification (RS) of Al-4Fe-4Ni and Al-4Fe-4Ni-5Mg alloys was performed by means of gas atomizing of the molten alloy and the spray deposition on the rotating water-cooled copper roll. Using typical powder metallurgy (PM) methods, i.e. cold pressing, vacuum degassing and hot extrusion, the RS-flakes were consolidated to the bulk PMmaterials. For comparison purposes, the conventionally cast and hot extruded Al-4Fe-4Ni and Al-4Fe-4Ni-5Mg alloys were studied as well. Mechanical properties of as-extruded materials were examined by compression tests performed at 293 K – 873 K. It was found that relatively high strength of as-extruded PM materials was accompanied by high ductility of samples deformed by hot compression test. Structural observations confirmed beneficial influence of rapid solidification on effective refining of intermetallic compounds, although some inhomogeneity of fine precipitates distribution was observed. Nevertheless, it was considered that an effective increase of the microhardness and strength of tested RS materials mostly result from achieved dispersion of structural components and can be intensified by solid solution hardening due to Mg-addition.

Characterization of AM60 Magnesium Alloy Prepared by Rapid Solidification and Plastic Consolidation Technique

Magnesium and its alloys are attractive candidates for automotive and aerospace applications due to their relatively high strength and low density. However, their low ductility determined by hcp structure of material results in limitation of plastic deformation processing. In order to improve ductility as well as mechanical properties, structure refinement processes can be used. It is well known that effective refining of the material structure can be achieved by increasing the cooling rate during casting procedures, hence rapid solidification process (RSP) has been experimented for the fabrication of magnesium alloys. The present paper reports an experimental investigation on the influence of rapid solidification on the mechanical properties of AM60 magnesium alloy. In order to obtain RS material melt spinning process was applied in protective atmosphere, resulting in formation of RS ribbons. Following consolidation of the RS material is necessary to obtain bulk material with high mechanical properties, as so hot extrusion process was applied. It was noticed that application of plastic consolidation by hot extrusion is the most effective process to achieve full densification of material. For comparison purposes, the conventionally cast and hot extruded AM60 alloy was studied as well. The purpose of the present study was to investigate in detail the effect of rapid solidification and extrusion temperature on the structure and mechanical properties of the materials.

Influence of Rapid Solidification of Cu-P Intermediate Alloy on Wear Resistance of Al-Si alloy

Abstract The influence of rapid solidification of Cu-P intermediate alloy on the wear resistance of Al-Si alloy is studied. TEM analysis indicates that at the cooling speed of 105-106 °C/s, the microstructure of melt-spin Cu-P ribbon consists of nano-grains and a little amount of amorphous areas, and the grain size of Cu3P in Cu-P intermediate alloy is decreased from 5-40 μm to 30-50 nm. Results show that the wear resistance of Al-Si alloy modified by melt-spin intermediate alloy are better than that of Al-Si alloy modified by massive ones; wear rate is decreased from 0.86% to 0.39%. Therefore, melt-spin treatment of Cu-P intermediate alloy is effective to improve the wear resistance of Al-Si alloy.

Rapidly Solidified Al-6Si-3Cu Alloy

Rapid solidification processes, RSP, are powerful tools to induce microstructural modifications, which may improve mechanical properties of alloys. In this paper the influence of rapid solidification on the formation of the undesirable brittle intermetallic compounds promoted by Si and Fe in Al-6Si-3Cu (A319-type) alloy have been investigated. The alloy have been casted using both conventional method and water-cooled wedge-copper mould. The microstructures have been evaluated by using a combination of X-ray diffraction, optical, scanning and transmission electron microscopy, and by Vickers microhardness. By increasing the cooling rate the length of the intermetallic β-Al5FeSi phase decreased, accompanying the same tendency of the secondary dendritic arm spacing. These results are accompanied by an increasing in hardness. Moreover, the formation and growth of the Al2Cu phase have been suppressed. These microstructural and hardness changes with the rapid solidification might be attributed to the increased solid solution content of the elements in the Al matrix.

Influence of Rapid Solidification on the Microstructure and Mechanical Properties of NiAl-Based Near Eutectic Alloys

The effects of rapid solidification on the microstructure and mechanical properties of two kinds of NiAl based eutectics were investigated. Rapid solidification resulted in the following effects, which encompass the refinement of the cell size, lamellar spacing and precipitates, deviation from the equilibrium composition, solubility extension, and a transition from a Heusler phase to an Hf-rich solid solution phase. Except for the deviation from the equilibrium composition, these microstructural characteristics are all beneficial to the improvement of mechanical properties. As a consequence, the room temperature compression yield strength and compression ductility were improved significantly and high temperature strength improved slightly. The high temperature compressive flow behaviour can be described by the temperature-compensated power-law equations.

Influence of rapid solidification on the microstructure of AZ91HP alloy

This paper presents differences of microstructure between conventionally casting and rapidly solidified AZ91HP alloy. The experimental results showed that rapid solidification changed the morphology of microstructure. The grain size was refined and homogeneously distributed β-Mg 17Al 12 phase was obtained. High cooling rate increased nucleation sites of α-Mg, refined microstructure and decreased the proportion of brittle β-Mg 17Al 12 in the eutectic (α-Mg and β-Mg 17Al 12). The decrease of microporosity should be attributed to the grain refinement and application of copper mould.

Metastable microstructures in rapidly solidified zirconium alloys

Zirconium alloys exhibit a wide variety of phase transformations. The present review outlines some aspects of phase transformations, which are encountered in rapidly solidified zirconium alloys. The possibility of solidification of unalloyed zirconium directly into the low temperature phase is examined and the role that solidification microstructure plays in modifying the β to α martensitic transformation in rapidly solidified material is discussed. Zirconium alloys undergo two types of displacive transformations, namely, the martensitic transformation and the ω transformation. The influence of rapid solidification on the transition from the martensitic to the ω transformation is also discussed. Addition of transition metals are known to depress the melting point of zirconium alloys very drastically. As a consequence, glass forming abilities of a number of binary and ternary zirconium alloys are quite strong. A number of zirconium based metal-metal amorphous alloys have been synthesized using rapid solidification. In recent years, this work has been extended to bulk metallic glasses, which usually contain a larger number of alloying elements. Crystallization of these glasses and quasi-crystalline phase formation in these systems is also discussed.

Influence of rapid solidification on the damping behaviour of some magnesium alloys

Rapid solidification processing of magnesium alloys leads to changes in their microstructure. This paper describes the damping behaviour of Mg, a series of Mg-Ca alloys and QE22 alloy prepared by rapid solidification. We use the logarithmic decrement as the characteristic parameter. The strain dependence of the logarithmic decrement exhibits two regions. At lower strains the logarithmic decrement is strain independent. In the second region the logarithmic decrement depends strongly on strain amplitude. The amplitude independent logarithmic decrement for the specimens prepared by rapid solidification is higher than that for cast specimens. The amplitude independent logarithmic decrement for Mg-Ca alloys prepared by rapid solidification decreases with increasing Ca concentration. Possible mechanisms are discussed.

Thermal analysis study of the influence of rapid solidification on the precipitation kinetics of theδ′ (Al3Li) Metastable phase in an Al-Mn-Li Alloy

The precipitation kinetics of theδ′ (Al3Li) phase in two rapidly solidified and one conventionally cast samples of an Al-2.3Li-6.5Mn (in wt%) alloy are compared. Following high cooling rates, manganese is retained in solid solution in the aluminium matrix (αAl) up to 6.0 wt%, far beyond the thermodynamic equilibrium value (0.36 wt% at 500°). Extended solid solution of manganese in aluminium induces strain gradients, similar to those produed by dislocations. The effect of such gradients, the size of which is proportional to the solute atomic fraction, is to enhance lithium precipitation, by lowering the activation energy, as observed, and also by affecting the rate parameter. Kinetic thermal analysis has been performed in a series of nonisothermal DTA experiments, operated in the heat flux DSC mode. The precipitation of theδ′ (Al3Li) phase is evidenced by an exothermic peak whose characteristics were analyzed. The rate of transformation (precipitation) is assumed to obey the Johnson-Mehl-Avrami equation. The activation energy for the precipitation process, as well as the kinetic rate parameter have been evaluated for the rapidly solidified and the conventionally cast specimens. The activation energy for precipitation is lowered, from 105 kJ·mol−1 for the conventionally cast material, down to 77 kJ·mol−1 for a sample that exhibits manganese solid solubility extension of 6.00 wt%. The rate parameter for the precipitation reaction is reduced from about 1.40 for the slowly cast sample to 1.20 the rapidly solidified sample, as a result of additional stress-assisted precipitation.

Rapid solidification effects in martensitic Cu-Zn-AI Alloys

The effects of rapid solidification on martensitic transformations were studied in Cu-Zn-AI samples prepared by the method of melt-spinning, with an estimated cooling rate of about 106 K per second near the freezing point. A diffusionless solidification reaction L → β occurs, and a very fine-grained β structure is obtained, with highly structured grain boundaries. The average β grain diameter (∼5 µm) is about two orders of magnitude smaller than that obtained by conventional solid state solution and quench treatment. The β:β grain boundaries contain extraordinary features such as large steps, and the matrix dislocation density is abnormally high. The Ms temperature is depressed significantly in as-melt-spun ribbon material, but as the martensitic transformation is cycled, it shifts upward in temperature and obtains a more narrow hysteresis loop. The martensite has the usual 9R structure (ABCBCACAB stacking) found in bulk alloys, and while the morphology is similar to that in bulk alloys, it is finer in scale. It is suggested that the β → 9R transformation is affected through the combined influence of rapid solidification on parent β grain size, disorder, β:β grain boundary structure, internal stresses, and dislocation substructure. Shape memory behavior is qualitatively similar in the rapidly solidified alloys.