Effect Of Solidification Rate Research Articles

Effect of solidification rate on the phase structure and electrochemical properties of alloy Zr 0.7Ti 0.3(MnVNi) 2

In this work, the alloy Zr 0.7Ti 0.3Mn 0.4V 0.4Ni 1.2 is selected and prepared through both arc-melting and melt-spinning processes at different solidification rates. The electrochemical tests have indicated that higher solidification rates lead to a higher discharge capacity when the solidification rates were <10 m s −1 and a lower discharge capacity when solidification rates were >10 m s −1. When solidification rates get higher, the cycling stability improves, but the activation property and the high-rate dischargeability of the melt-spun alloy both get worse noticeably. The XRD results indicate that the as-cast alloy and the melt-spun alloys all contains two Laves phases, C14 and C15, but the phase composition and phase abundance of the alloys are quite different from each other. The SEM and EPMA results indicate that the microstructure of melt-spun alloy is a uniform mixture of very fine dendritic and columnar crystalline structures, while the as-cast alloy is of much coarser dendritic crystalline structure with noticeable composition segregation. It is the difference in phase composition, phase abundance, and microstructure that results in the noticeable difference in electrochemical properties.

The effect of solidification rate on the microstructure and electrochemical properties of Co-free [formula omitted] alloys

In this work, Fe-containing Co-free Ml(NiMnAlFe) 5 alloy samples were prepared by both arc-melting and melt-spinning processes at different solidification rates, and tested for electrochemical performance. The electrochemical tests indicated that higher solidification rates led to a better cycling stability, but lower discharge capacity and high-rate dischargeability. The X-ray diffraction results indicated that the as-cast alloy and the melt-spun alloys were both of the CaCu 5 -type structure single phase, but the lattice constants of the alloys were varying. The scanning electron microscope and EPMA results indicated that the microstructure of melt-spun alloy formed at the relative lower solidification rate (5 m/ s) was of very fine dendritic structure and that for the alloy formed at a relative higher solidification rate (15 m/ s) was of cellular structure, and both had a more homogeneous composition than the as-cast alloy, which had a typical dendrite structure with noticeable composition segregation. The Co-free MlNi 4.1 Mn 0.35 Al 0.3 Fe 0.25 prepared by melt-spinning at 15 m/ s rate is a promising candidate for low-cost electrode alloy.

The Effect of Solidification Rates and Thermal Gradients on Directionally Solidified Microsturucture in the Ni-Base Superally GTD111M

Morphological evolution and growth mechanism at the solid/liquid interface during solidification were investigated in the Ni-base superalloy GTD111M by directional soldification and quenching(DSQ) technique. The experiments were conducted by changing solidification rate(V) and thermal gradient(G) which are major solidification process variables. High thermal gradient condition could be obtained by increasing the furnace temperature and closely attaching the heating and cooling zones in the Bridgeman type furnace. The dendritic/equiaxed transition was found in the G/V value lower than <TEX>$0.05<TEX>$\times$</TEX>10{^3}^{\circ}C$</TEX>s/<TEX>$\textrm{mm}^2$</TEX>, and the planar interface of the MC-<TEX>${\gamma}$</TEX> eutectic was found under <TEX>$17 <TEX>$\times$</TEX> 10{^3}^{\circ}C$</TEX> s/<TEX>$\textrm{mm}^2$</TEX>. It was confirmed that the dendrite spacing depended on the cooling rate(GV), and the primary spacing was affected by the thermal gradient more than solidification rate. The dendrite lengths were decreased as increasing the thermal graditne, and the dendrite tip temperature was close to the liquidus temperature at <TEX>$50 \mu\textrm{m}$</TEX>/s.

Effects of solidification rate and ageing on the microstructure and mechanical properties of AZ91 alloy

Sand-cast plates of a commercial AZ91C alloy have been used for the study. Varying the solidification rate by placing large cast-iron chills in the mould produced a range of secondary dendrite arm spacing (SDAS) within the cast plates. The plates were solution heat-treated, quenched and aged at 165 °C for up to 350 h. The SDAS (μm) varied with the solidification time, tf (s), as SDAS=5.3 tf0.43. The tensile ductility in the as-quenched (T4) condition did not depend on the solidification rate whilst in the T6 condition it tended to decrease for slowly solidified material (SDAS>50 μm). The yield strength and hardness increased and the ductility decreased with ageing. The fracture mode changed from predominantly transgranular in the T4 condition to predominantly intergranular in the T6 condition. The properties of the sand-castings are compared with those of high-pressure diecastings and the possible strengthening mechanisms are discussed. A number of areas that require more research are pointed out.

Microstructure evolution of Ni, Cr, Al–TaC in situ composite directionally solidified under a high temperature gradient

The effect of solidification rate on the solidified structure, solute segregation and microstructures such as TaC rods volume fraction, TaC rods average spacing, TaC average transverse area and γ′ phase were experimentally investigated under a high temperature gradient by employing a method of directional solidification with liquid metal cooling. Three types of the solidified structure were identified: planar, cellular and dendritic. Both solidified structure and solidification rate had an effect on the eutectic morphologies. The TaC rods volume fraction could be changed with increasing solidification rate. TaC average inter-rods spacing and TaC average transverse areas decreased, the PS (parameter of shape) of γ′ tends to one and the size of γ′ phase decreased with increasing solidification rate.

The effect of solidification rate on the structure of magnesium-aluminium eutectic grains

A magnesium-aluminium alloy of eutectic composition was solidified under two different cooling conditions, producing a low and a high growth rate of the eutectic solid-liquid interface. The high growth rate specimen contained smaller eutectic grains and cells, with a smaller interphase spacing compared with the low growth rate specimen. The high growth rate specimen also contained some primary Mg17Al12 dendrites, suggesting that the coupled zone is skewed towards the Mg phase with increased undercooling. A lamellar eutectic morphology was observed in the low growth rate specimen, while the morphology was fibrous in the high growth rate specimen.

A rationale for the quality index of Al-Si-Mg casting alloys

The quality index introduced on empirical grounds by Drouzy, Jacob and Richard1 is widely used by the casting industry as a tool for predicting the effect of solidification rate, chemical additions and heat treatment on the ductility and tensile strength of Al-7Si-Mg casting alloys. A drawback of the approach is its lack of physical justification. A simple analytical model is used to derive the quality index charts for A1-7Si-0.4 Mg alloys and to provide a physical meaning to the parameters involved. It is shown that the quality index relates to the fraction of uniform deformation available to the material. The application of the concept to Cu-containing alloys is also discussed.

Relationship between η phase formation and solidification rate in directionally solidified IN792 + Hf alloy

The effect of solidification rate on the formation of η phase in a directionally solidified IN792 + Hf superalloy was studied. A Cr rich ‘precipitate free zone’ adjacent to the eutectic (γ + γ′) was noticed in the quenched directionally solidified microstructure of the alloy. The formation of the precipitate free zone was due to the solidification of eutectic (γ + γ′) which consumed a large amount of the γ′ forming elements and increased the ratio of (Ti + Hf + Ta + W)/Al in the residual liquid. The high ratio of (Ti + Hf + Ta + W)/Al in the final residual liquid induced the formation of η phase and hence η phase always appeared at the boundary between the eutectic regions and the dendrite core regions. The ratio of (Ti + Hf + Ta + W)/Al was decreased by the diffusion of elements between the residual liquid and the surrounding area. A lower solidification rate favoured the back diffusion and decreased the ratio of (Ti + Hf + Ta + W)/Al in the residual liquid, and hence reduced the formation of η phase.

Influence of solidification rate on precipitation and microstructure of directional solidification IN792 + Hf superalloy

The effect of solidification rate on the precipitation and microstructure of directional solidification IN792 + Hf alloy was studied. The solidification sequence and the initial precipitation temperature of different phases were determined by the observation of the quenched microstructure combined with the differential thermal analysis measurement. The script carbide was turned into faceted carbide with the drop of solidification rate. It was concluded by microstructure analysis that the faceted carbide was pushed by the γ solid front before it was captured. The incorporation of γ phase into the faceted carbide was due to the dendrite growth of the carbide toward one point and the mergence of the dendrites. Some long carbide bars were formed along the grain boundaries by continual reaction of eutectic (γ + MC carbide) at a solidification rate of 0.5 μm/s. Two zones, the γ′ forming elements enriched zone and depleted zone, were found in the residual liquid area. Eutectic γ/γ′ nucleated in the γ′ forming elements enriched zone. The η-phase precipitation was controlled by the ratio of (Ti + Hf + Ta + W)/Al in the residual liquid. The growth of eutectic γ/γ′ increased the ratio and induced the η-phase precipitation. A lower solidification rate decreased the ratio by sufficient diffusion and hence efficiently suppressed the η-phase precipitation.

一方向凝固法によるYBCO/Ag複合超伝導体中のAg分布に及ぼす凝固速度の影響

一方向凝固法によるYBCO/Ag複合超伝導体中のAg分布に及ぼす凝固速度の影響

Effect of Solidification Rate and Temperature Gradient on the Changes of Mushy Zone Length in Pb-36mass%Sn Binary Alloys during Upward Directional Solidification.

Upward directional solidification experiments have been carried out on Pb-36mass%Sn binary alloys with varying the solidification rate and temperature gradient. Results show that due to solute convection, the length of the mushy zone was not constant even when the dendritic growth at a constant temperature gradient was maintained during upward directional solidification. The length of the mushy zone decreased with increasing fraction solidified if solute convection occured. At a constant solidification rate, the greater the temperature gradient is, the greater the change of length of mushy zone is. At a constant temperature gradient, the smaller the solidification rate is, the greater the change in length of the mushy zone is. Effect of solute convection on the length of the mushy zone during upward directional solidification is responsible for the composition change of Sn at ahead of the mushy zone. If the composition at ahead of the mushy zone changes greatly as increasing the fraction solidified, the change of length of the mushy zone is greater.

A rationale for the quality index of Al-Si-Mg casting alloys

The quality index introduced on empirical grounds by Drouzy, Jacob and Richard1 is widely used by the casting industry as a tool for predicting the effect of solidification rate, chemical additions and heat treatment on the ductility and tensile strength of Al-7Si-Mg casting alloys. A drawback of the approach is its lack of physical justification. A simple analytical model is used to derive the quality index charts for A1-7Si-0.4 Mg alloys and to provide a physical meaning to the parameters involved. It is shown that the quality index relates to the fraction of uniform deformation available to the material. The application of the concept to Cu-containing alloys is also discussed.

Microsegregation of manganese and silicon in high manganese ductile iron

Manganese is known as an inexpensive element and a potent promoter of hardenabilty in ductile iron but it also segregates severely and encourages the formation of carbides in the matrix. Thus, it is suggested that when the Mn content is high, attempts should be made to minimise the Mn segregation. In the present work the effect of solidification rate and homogenisation treatment on the severity of segregation of Mn and Si in several types of wear resistant high Mn ductile iron was investigated. It is demonstrated that increasing the solidification rate, leading to a high nodule count, decreases not only the heterogeneity of these elements but also the carbide content.

The effect of cooling rate from the melt on the recrystallization behavior of aluminum alloy 6013

In most commercial operations, the plant metallurgist likely has little control over the solidification rate of the process. However, solidification rate is affected by the dimensions of the ingot, and product form (plate ingot vs extrusion billet, for example) determines the dimensions of the ingot to be cast. Consequently, understanding the effects of solidification rate might be useful in explaining differences in microstructure that are often observed in various product forms cast from equivalent compositions. To provide this microstructural information, the effect of cooling rate from the melt on the microstructural changes in hot-rolled and solution heat treated (SHT) aluminum alloy 6013 was investigated. The range of cooling rates in this investigation is comparable to what might be observed through the thickness of a plate ingot. Over the cooling rate range investigated (0.5 to 5 K/s), recrystallization behavior of the alloy appears to be primarily affected by the size and number density of the coarse α(AlFeMnSi) constituent particles, which act as sites for particle stimulated nucleation (PSN) of recrystallized grains. At intermediate cooling rates (1.5 K/s), the resistance to recrystallization is at a minimum. As the cooling rate increases beyond 1.5 K/s, the number of particles available for PSN decreases; thus, there is a decrease in the fraction of recrystallized grains after heat treating. On the other hand, as the cooling rate is decreased from 1.5 K/s, the size of the constituents increases; however, their number decreases, once again leading to a decrease in the fraction of recrystallized grains observed after heat treatment.

Effect of Solidification Rate on the Microstructure of a Ni-Base Superalloy

The effect of solidification rate on the solidified structure, solute segregation and microstructures such as carbide, gamma'gamma eutectic, gamma' phase and dendrite arm spacing was experimentally investigated employing a method of partially directional solidification and subsequent quick quenching. Three types of the solidified structure were identified: cellular, cellular-dendritic and developed dendrite-type, and the width of a mushy zone was narrowed when solidification rate increased from 2.5 mu m/s to 125 mu m/s. The carbide morphologies were affected by both solidified structure and solidification rate, it formed into bar-type in the cellular structure, and Chinese script-type in the dendrite structure. The increase of solidification rate caused a lot of gamma'/gamma eutectic and the change of gamma' phase from cubic into cubic-round. The dendrite arm spacing decreased and the segregation of Cr, Al, Co, Mo, Ti was alleviated with increasing solidification rate.

Effect of solidification rate and metal feedability on porosity and [formula omitted] particle distribution in an Al-Si-Mg (359) alloy

In the production of particle-reinforced metal-matrix composite castings, particle sedimentation during the melting process and particle redistribution during solidification can lead to particle segregation in the as-cast structure, the effects of which, in addition to those of porosity, can be highly detrimental to the properties and quality of the casting. Solidification rate and metal feedability are considered mainly responsible for the two problems. The present work reports on the influence of these factors on the particle distribution and porosity in 359 alloy composites reinforced with SiC and Al 2O 3 particles. The results show that the microporosity observed in 359/SiC (p) composites is a consequence of pore nucleation at the SiC particle sites and hindered liquid metal flow due to particle clustering; the former is responsible for the skewed porosity distribution profiles typically observed in these composites, similar to the type I distributions observed in A356 alloy. In the 359/Al 2O 3(p) composite, limited feedability and the wider range or larger particle sizes of the alumina particles result in the bell-shaped porosity profile observed, as well as the larger maximum pore size range (100–180 μm 2 against 0–40 μm 2 for the SiC (p) composites). The interparticle distance distributions for the SiC (p) composites show that finer dendrite arm spacings (DASs) produce a more uniform distribution of the SiC particles, while higher spacings lead to particle clustering, usually at separations of about 5 μm, the probability increasing with increase in SiC (p) content. In the 359/Al 2O 3(p) composite, the distribution profile changes from a normal, random distribution to an exponential type as the DAS is increased. Together with the microstructural observations, the distributions indicate that particle pushing is the dominant phenomenon in the SiC (p) composites during solidification, whereas in the Al 2O 3(p) composite, mechanical trapping of the particles takes place at smaller DASs, that changes to particle pushing at larger spacings.

Effect of solidification rate (0.1–100°C s −1) on the microstructure, mechanical properties and fractography of two AlSi-10vol.%SiC particle composite castings

The present work was performed on two Duralcan SiC-particle-reinforced composites containing 10 vol.% SiC particles. The result show that the as-cast properties of these composites are basically controlled by the solidification rate. Higher solidification rates promote homogeneous distribution of the SiC particles. The fracture mode in these composites is complex. The crack propagates through the matrix and through the particle-matrix interface owing to the opening up of voids. Extension of cracked SiC particles and voiding depends on the localized stresses and interfacial strength.

Structural and Morphological Investigation of Vanadium White Cast Irons

The metallurgical structure of a new family of cast irons has been studied in relationship to phase equilibria and solidification morphology. These alloys contain vanadium and chromium in proportions optimised to enhance, principally, the formation of eutectic VC carbides. Investigational work consisted of differential thermal analysis experiments, characterisation of the phases and directional solidification experiments. The stability of solidification carbides during a slow cooling process was examined. The effect of solidification rate was examined by measuring the average secondary arm dendrite spacings. A comparison was established with results for high carbon steels.

ラネー銅触媒組織とアクリロニトリル水和反応における触媒活性におよぼす母合金凝固速度の影響

ラネー銅触媒組織とアクリロニトリル水和反応における触媒活性におよぼす母合金凝固速度の影響

Study on formation of channel-type segregation

The formation condition of channel-type segregation was investigated systematically using unidirectionally solidified Al-Mg and Al-Mg-Cu alloys. In the Al-Mg alloys, the liquid density (ρL) in the solid-liquid region, which is directly related to the formation of channel-type seg-regation, decreases with the progress of solidification. Addition of copper offsets this density decrease. The effects of solidification rate, temperature gradient, composition, and inclination angle of specimens on the formation of channel-type segregation were studied in detail Channel-type segregation similar to that in steel ingots and directionally solidified superalloys appeared in these aluminum alloys below the critical solidification rate,Rc. The experimental results showed thatRc depended mainly on the thermal and solutal density change of the interdendritic liquid and the inclination angle of the solidification interface to the horizontal plane