Stage Of Spinodal Decomposition Research Articles

Fine-Tuning Melt Pools and Microstructures: Taming Cracks in Powder Bed Fusion—Laser Beam of a non-weldable Ni-base Superalloy

Powder Bed Fusion – Laser Beam (PBF-LB) of high γ’ strengthened Ni-base superalloys, such as CM247LC, is of great interest for high temperature applications in gas turbines. However, PBF-LB of CM247LC is challenging due to the high cracking susceptibility during PBF-LB processing (solidification cracking) and heat treatment (strain age cracking, mostly caused by residual stresses). This study focuses on understanding the impact of process parameters on microstructure, residual stresses and solidification cracking. Laser power (P), speed (v) and hatch spacing (h) were varied while the layer thickness (t) was fixed. The melt pool size and shape were found to be key factors in minimizing solidification cracking. Narrower and shallower melt pools, achieved using a low line energy density (LED = P/v ≤ 0.1 J/mm), gave low crack densities (0.7 mm/mm2). A tight hatch spacing (h = 0.03 mm) resulted in reduced lack of fusion porosity. Electron backscatter diffraction investigations revealed that parameters giving finer microstructure with 〈100〉 crystallographic texture had low crack densities provided they were processed with a low LED. Atom probe tomography elucidated early stages of spinodal decomposition in the as-built condition, where Cr and Al cluster separately. The extent of spinodal decomposition was found to be affected by the LED and the hatch spacing. Samples with low LED and small hatch spacing showed higher degrees of spinodal decomposition. X-ray diffraction residual stress investigations revealed that the residual stress is proportional to the volumetric energy density (VED = P/(v. h. t)). Although low residual stresses can be achieved by using low VED, there is a high risk of lack of fusion. Hence, other parameters such as modified scan strategy, build plate pre-heating and pulsed laser mode, must be further explored to minimize the residual stresses to reduce the strain age cracking susceptibility.

Spinodal strain glass in Mn-Cu alloys

Strain glasses (STGs), which are characterized by nanodomains of martensite formed via a strain glass transition, can produce many unusual properties not possessed by normal martensitic alloys. These nanodomains originate from the formation of short-range strain ordering by the disruption of otherwise long-range strain ordering or normal martensitic transformation through sufficient atomic/nanoscale random stress/strain field. So far the atomic/nanoscale randomness is known to be from either point defects, dislocations, or nanoprecipitates. Here we report a spinodal STG alloy Mn60Cu40, which stems from nanoscale composition modulations (5-20 nm) formed in the early stage of spinodal decomposition, which is identified by STEM-EDS and HRTEM. For short-time (<50 min) aged sample, a strain glass transition was identified by its typical signatures including invariance of global face-centered cubic (fcc) structure with cooling, frequency dependence of elastic moduli at STG transition temperature (Tg) following a Vogel-Fulcher relationship, non-ergodicity as manifested by zero-field-colling/field-cooling curves, and the formation of martensitic face-centered tetragonal (fct) nanodomains. For long-time (≥50 min) aged sample, a normal martensitic transition from fcc to fct appears with cooling, being consistent with literatures. As the result, a temperature vs. aging-time phase diagram of spinodal STG was established and shows a crossover from STG to martensite above a critical aging time. The spinodal STG exhibits a non-magnetic Elinvar behavior, i.e., nearly constant elastic modulus over a wide temperature range, together with high-damping capacity. We anticipate that the spinodal STG and associated novel properties may also be found in other metallic and ceramic spinodal materials.

Exploration of spinodal decomposition in multi-principal element alloys (MPEAs) using CALPHAD modeling

Researchers attributed the orderly arranged nanoscale phases observed in many multi-principal element alloys (MPEAs) to spinodal/spinodal-mediated phase transformation pathways. However, spinodal decomposition is not well understood in multicomponent systems. Although the theoretical background is available, CALPHAD databases were not used to explore the miscibility gap in MPEAs. In this work, we develop a CALPHAD framework utilizing the Hessian of free energy to study the stability of solid solutions in MPEAs. In particular, we utilize the geometry of higher dimensional Gibbs simplex in conjunction with the Hessian to calculate concentration modulations in early stages of spinodal decomposition. We apply this framework to a diverse set of multi-phase MPEAs that have been studied in the literature including TiZrNbTa (BCC/BCC), Fe15Co15Ni20Mn20Cu30 (FCC/FCC), Al0.5NbTa0.8Ti1.5V0.2Zr (BCC/B2), AlCo0.4Cr0.6FeNi (BCC/B2) and Al0.5Cr0.9FeNi2.5V0.2 (FCC/L12). We show that the MPEA systems are unstable only to certain concentration modulations which could be further explored to design microstructurally engineered alloys.

New insights into the hardening and pitting corrosion mechanisms of thermally aged duplex stainless steel at 475 °C: A comparative study between 2205 and 2101 steels

• Ferrite hardening is caused by α'-α phase separation. • In LDSS 2101, Cr nitrides impact pitting corrosion more than α'-evolution. • G-phase contributes to a decrease in pitting corrosion in long-term aging. • Spinodal decomposition is the main cause of the drop-in pitting corrosion of DSS 2205. In this study, the relationship between spinodal decomposition and the formation of Ni-rich clusters and G-phase in the ferrite on hardening and pitting corrosion of two thermally aged duplex stainless steels (DSSs) at 475 °C was investigated. Results indicate that, for 2205 DSS, pitting corrosion behavior is influenced by the presence and size of G-phase precipitates for longer aging times, but this contribution is masked by the advanced stage of spinodal decomposition in the ferritic structure. On the other hand, for 2101 DSS, the formation of Cr-richer nitrides impairs pitting corrosion resistance more than spinodal decomposition.

Structural origin of the weak germanate anomaly in lead germanate glass properties

AbstractBinary PbO–GeO2 glasses have been studied in detail from 5 to 75 mol% PbO using high‐resolution neutron diffraction, high‐energy X‐ray diffraction, 207‐Pb NMR, pycnometry, and thermal analysis. The Ge–O coordination number displays a broad maximum nGeO = 4.14(3) close to 27 mol% PbO. This is smaller than the maximum nGeO = 4.3 reported in CaO–GeO2 glasses but occurs at a similar composition. This structural behavior appears to explain the relatively weak germanate anomaly manifest in lead germanate glasses, for example as a maximum in the measured atom number density and a plateau in the glass transition temperatures. The structural role of Pb(II) is complex. On the one hand, short covalent Pb–O bonds and small Pb–O coordination numbers of ∼3 to 4 indicate glass network former character for Pb(II), associated with a stereochemically active electron lone pair. On the other hand, the presence of some GeO5 or GeO6 units, in addition to the majority GeO4 tetrahedral species, indicates some modifier character of Pb(II) at low PbO contents, giving rise to the observed weak germanate anomaly, as well as elongation and enhanced ionicity of the Pb–O bonds. Overall, the observed structural behavior of Pb(II) in lead germanate glasses appears as intermediate between that observed in lead silicate and lead borate glasses. Despite rapid quenching, at low PbO contents, the glasses studied exhibited nanoscale heterogeneity, evidenced by small‐angle X‐ray scattering consistent with the early stages of spinodal decomposition.

Correlation between X-Ray diffraction pattern and microstructure of surface of E690 high-strength steel induced by laser-shock processing

To examine the relationship between the X-ray Diffraction (XRD) pattern and microstructure of the surface of E690 high-strength steel induced by laser shocks, X-ray diffractometry and transmission electron microscopy (TEM) were used to detect the laser-impact zone on the steel surface to obtain its diffraction pattern and microstructural morphology, followed by the establishment of a surface microstructure response model of the E690 high-strength steel under laser shock. The grain size of the impacted surface decreased with an increase in laser power density (LPD). When the LPD reached 4.07 GW/cm2, Ostwald ripening was observed in the TEM images and the grain size increased during the later stages of spinodal decomposition. When the LPD was 5.09 GW/cm2, nanograins were detected on the surface of the laser-impacted area. The X-ray diffraction result on the surface of the E690 high-strength steel was consistent with the microstructural analysis using TEM, which proves that the microstructural response of E690 high-strength steel under laser shock can be described by the surface microstructure response model.

Interplay between Kinetics and Dynamics of Liquid-Liquid Phase Separation in a Protein Solution Revealed by Coherent X-ray Spectroscopy.

Microscopic dynamics of complex fluids in the early stage of spinodal decomposition (SD) is strongly intertwined with the kinetics of structural evolution, which makes a quantitative characterization challenging. In this work, we use X-ray photon correlation spectroscopy to study the dynamics and kinetics of a protein solution undergoing liquid-liquid phase separation (LLPS). We demonstrate that in the early stage of SD, the kinetics relaxation is up to 40 times slower than the dynamics and thus can be decoupled. The microscopic dynamics can be well described by hyper-diffusive ballistic motions with a relaxation time exponentially growing with time in the early stage followed by a power-law increase with fluctuations. These experimental results are further supported by simulations based on the Cahn-Hilliard equation. The established framework is applicable to other condensed matter and biological systems undergoing phase transitions and may also inspire further theoretical work.

Existence and Continuity of Inertial Manifolds for the Hyperbolic Relaxation of the Viscous Cahn–Hilliard Equation

We consider the hyperbolic relaxation of the viscous Cahn–Hilliard equation 0.1 $$\begin{aligned} \varepsilon \phi _{tt}+ \phi _t-\Delta (\delta \phi _t-\Delta \phi + g(\phi ))=0, \end{aligned}$$ in a bounded domain of $${\mathbb R}^d$$ with smooth boundary when subject to Neumann boundary conditions, and on rectangular domains when subject to periodic boundary conditions. The space dimension is $$d=1,$$ 2 or 3, but it is required $$\delta =\varepsilon =0$$ when $$d=2$$ or 3; $$\delta $$ being the viscosity parameter. The constant $$\varepsilon \in (0,1]$$ is a relaxation parameter, $$\phi $$ is the order parameter and $$g:{\mathbb R}\rightarrow {\mathbb R}$$ is a nonlinear function. This equation models the early stages of spinodal decomposition in certain glasses. Assuming that $$\varepsilon $$ is dominated from above by $$\delta $$ when $$d=2$$ or 3, we construct a family of exponential attractors for Eq. (0.1) which converges as $$(\varepsilon ,\delta )$$ goes to $$(0,\delta _0),$$ for any $$\delta _0\in [0,1],$$ with respect to a metric that depends only on $$\varepsilon $$ , improving previous results where this metric also depends on $$\delta $$ . Then we introduce two change of variables and corresponding problems, in the case of rectangular domains and $$d=1$$ or 2 only. First, we set $$\tilde{\phi }(t)=\phi (\sqrt{\varepsilon } t)$$ and we rewrite Eq. (0.1) in the variables $$(\tilde{\phi },\tilde{\phi }_t).$$ We show that there exist an integer n, independent of both $$\varepsilon $$ and $$\delta $$ , a value $$0<\tilde{\varepsilon }_0(n)\le 1$$ and an inertial manifold of dimension n, for either $$\varepsilon \in (0,\tilde{\varepsilon }_0]$$ and $$\delta =2\sqrt{\varepsilon }$$ or $$\varepsilon \in (0,\tilde{\varepsilon }_0]$$ and $$\delta \in [0,3\varepsilon ]$$ . Then, we prove the existence of an inertial manifold of dimension that depends on $$\varepsilon $$ , but is independent of $$\delta $$ and $$\eta $$ , for any fixed $$\varepsilon \in (0,(\eta -2)^2]$$ and every $$\delta \in [\varepsilon ,(2-\eta )\sqrt{\varepsilon }]$$ , for an arbitrary $$\eta \in (1,2)$$ . Next, we show the existence of an inertial manifold of dimension that depends on $$\varepsilon $$ and $$\eta $$ , but is independent of $$\delta $$ , for any fixed $$\varepsilon \in (0,\frac{1}{(2+\eta )^2}]$$ and every $$\delta \in [(2+\eta )\sqrt{\varepsilon },1]$$ , where $$\eta >0$$ is arbitrary chosen. Moreover, we show the continuity of the inertial manifolds at $$\delta =\delta _0,$$ for any $$\delta _0\in [0,(2-\eta )\sqrt{\varepsilon }]\cup [(2+\eta )\sqrt{\varepsilon },1]$$ . Second, we set $$\phi _t=-(2\varepsilon )^{-1}(I-\delta \Delta )\phi +\varepsilon ^{-1/2}v$$ and we rewrite Eq. (0.1) in the variables $$(\phi ,v)$$ . Then, we prove the existence of an inertial manifold of dimension that depends on $$\delta $$ , but is independent of $$\varepsilon ,$$ for any fixed $$\delta \in (0,1]$$ and every $$\varepsilon \in (0,\frac{3}{16}\delta ^2]$$ . In addition, we prove the convergence of the inertial manifolds when $$\varepsilon \rightarrow 0^+$$ .

In situ observation of the dynamics in the middle stage of spinodal decomposition of a silicate glass via scanning transmission electron microscopy

Real-space observations in the middle stage of spinodal decomposition have not been achieved because of the small sizes and unclear interfaces of the phases. Here, we performed in situ real-space experiments with heating to quantitatively reveal the local dynamics and structures of a calcium aluminosilicate glass in the middle stage of spinodal decomposition by scanning transmission electron microscopy. This glass separate into CaO–Al2O3–SiO2 phase and SiO2 phases. The observations revealed that the CaO–Al2O3–SiO2 phases with low Ca concentrations behaved as if they were in the middle stage, whereas the CaO–Al2O3–SiO2 phases with high Ca concentrations coarsened as if they were in the final stage. This coexistence of stages suggested that the behaviors of the phases depend not only on time, but also on their local relative concentrations. Differing from the well-known final stage of spinodal decomposition, the phases with relatively high Ca concentrations in the middle stage showed peculiar directional migration guided by the phases with relatively low Ca concentrations. These findings have not been observed before and thus have the potential to provide a new way to control the phase-separated structure.

Rayleigh–Benard Instability: a Study by the Methods of Cahn–Hillard Theory of Nonequilibrium Phase Transitions

This article is an attempt to study the process of Rayleigh–Benard convective instability by the methods used for mathematical modeling of critical phenomena as nonequilibrium phase transitions in their initial stages of spinodal decomposition. We show that it is possible to extend the formalism adopted in the Cahn–Hillard theory of nonequilibrium phase transitions and perfected on problems of highgradient crystallization to other types of problems, in particular, those pertaining to the Rayleigh–Benard convective instability. For the initial stage of instability, a model is constructed that represents it as a nonequilibrium phase transition due to diffusive stratification. It is shown that the Gibbs free energy of deviation from the homogeneous state (with respect to the instability under consideration) is an analogue of the Ginsburg–Landau potential. Numerical experiments, by means of boundary temperature control, have been conducted with regard to self-excitation of the homogeneous state. Numerical analysis shows that convective flows may appear and proceed from regular forms (the so-called regular structures) to nonregular flows through a chaotization of the process. External factors, such as temperature growth, may lead to chaos via period doubling bifurcations.

Phase-field simulation of spinodal phase separation in the Na2O-SiO2 glasses

The phase-field method was used for the kinetic simulation of the spinodal phase separation of glasses in the Na2O-SiO2 system. The miscibility gap and spinodal curve were calculated based on the previous interaction parameters of the liquid phase. The kinetic simulations showed that the resultant morphology depended on the initial concentration and the temperature. In the early stages of spinodal decomposition, the interconnected structure developed continuously and in the later stages began to coarsen. During the coarsening stage, the evolution of morphology of the microstructures could result in the discrete spherical particles as well as the interconnected structure, depending on the heat treatment condition. To analyze the phase separation rate, the amplification factors for the initial concentrations were calculated as a function of temperature and could explain the morphology developed from the present simulation. Also, the present work could explain the evolution of experimental morphologies available in the literature reasonably.

The Effect of Nonisothermality on the Early Stages of Spinodal Decomposition

A nonisothertmal model of spinodal decomposition is proposed for a binary system described by the Ginzburg–Landau energy. The initial stages of spinodal decomposition are investigated for a system of simultaneous equations describing the impurity and temperature redistribution. The dispersion equation and the instability growth rate of spinodal structures are obtained. The temperature dependence of the growth rate and the wave number corresponding to the maximum instability is found. The observed difference in the dispersion relations of isothermal and nonisothermal models shows that a criterion for the effect of temperature fluctuations on the spinodal decomposition is given by a dimensionless parameter Γ; for large values of Γ (Γ ≥ 1000), temperature fluctuations in the form of noise are certainly insufficient for spinodal decomposition due to a change in the dispersion structure of the equations, which suggests the need to take into account the nonisothermal behavior of the system.

Morphological Simulation of Phase Separation Coupled Oscillation Shear and Varying Temperature Fields

This paper explores the effect of the shear frequency and Prandtl number (Pr) on the procedure and pattern formation of phase separation in symmetric and asymmetric systems. For the symmetric system, the periodic shear significantly prolongs the spinodal decomposition stage and enlarges the separated domain in domain growth stage. By adjusting the Pr and shear frequency, the number and orientation of separated steady layer structures can be controlled during domain stretch stage. The numerical results indicate that the increase in Pr and decrease in the shear frequency can significantly increase in the layer number of the lamellar structure, which relates to the decrease in domain size. Furthermore, the lamellar orientation parallel to the shear direction is altered into that perpendicular to the shear direction by further increasing the shear frequency, and also similar results for larger systems. For asymmetric system, the quantitative analysis shows that the decrease in the shear frequency enlarges the size of separated minority phases. These numerical results provide guidance for setting the optimum condition for the phase separation under periodic shear and slow cooling.

Pattern formation mechanisms in sphere-forming diblock copolymer thin films

The order-disorder transition of a sphere-forming block copolymer thin film was numerically studied through a Cahn-Hilliard model. Simulations show that the fundamental mechanisms of pattern formation are spinodal decomposition and nucleation and growth. The range of validity of each relaxation process is controlled by the spinodal and order-disorder temperatures. The initial stages of spinodal decomposition are well approximated by a linear analysis of the evolution equation of the system. In the metastable region, the critical size for nucleation diverges upon approaching the order--disorder transition, and reduces to the size of a single domain as the spinodal is approached. Grain boundaries and topological defects inhibit the formation of superheated phases above the order--disorder temperature. The numerical results are in good qualitative agreement with experimental data on sphere-forming diblock copolymer thin films.&#x0D; Received: 22 August 2017, Accepted: 12 December 2017; Edited by: R. Dickman; Reviewed by: A. Peters, Dept. Chemical Engineering, Louisiana Tech Univ., Ruston, USA; DOI: http://dx.doi.org/10.4279/PIP.100001&#x0D; Cite as: L R Gómez, N A García, R A Register, D A Vega, Papers in Physics 10, 100001 (2018)&#x0D; This paper, by L R Gómez, N A García, R A Register, D A Vega, is licensed under the Creative Commons Attribution License 4.0.

Análisis de la descomposición espinodal en aleaciones Fe-32 y 40 %at. Cr utilizando el método de campo de fases basado en las ecuaciones lineal y no lineal de Cahn y Hilliard

La descomposición espinodal se estudió durante el envejecido de aleaciones Fe-Cr mediante la solución numérica de las ecuaciones diferenciales parciales lineal y no linear de Cahn y Hilliard usando el método de diferencias finito explícito. Los resultados de la simulación numérica permitieron describir apropiadamente el mecanismo, morfología y cinética de la descomposición de fases durante el envejecido isotérmico de estas aleaciones. La cinética de crecimiento de la descomposición de fases ocurrió muy lentamente durante las primeras etapas de envejecido, y se incrementó considerablemente con el tiempo de envejecido. La ecuación no lineal parece ser más apropiada para describir las primeras etapas de la descomposición espinodal que la ecuación lineal.

Lattice Boltzmann simulation of phase separation under dynamic temperature and shear: Coupling effects of shear convection and thermal diffusion.

This paper presents an exploration of the separation behavior and pattern formation in a shear binary fluid with dynamic temperature after slow cooling via coupled lattice Boltzmann method. The phase separation procedure can be divided into three different stages: spinodal decomposition, domain growth, and domain stretch. The effect of thermal diffusion was observed to be more significant than that of shear convection in the spinodal decomposition stage, while the opposite was observed in the domain growth stage. The slow cooling temperature field significantly prolonged the spinodal decomposition stage, and decreased the separated domain size in domain growth stage. The phase behavior and pattern formation from the disordered state into the coexistence state after slow cooling was investigated during the domain stretch stage. Two typical length scales were obtained according to the equilibrium of two phases, where the number of layers in the corresponding domains was controllable by adjusting the Prandtl number for systems of different scales. The manner in which various viscosities and thermal diffusivities influence the morphologies and kinetic characterizations of the materials was also demonstrated: numerical results indicated that decrease in viscosity can cause increase in the growth exponents of separation fronts and velocity of domain growth, as well as increase in thermal diffusion.

Kinetics of liquid-liquid phase separation in protein solutions exhibiting LCST phase behavior studied by time-resolved USAXS and VSANS.

We study the kinetics of the liquid-liquid phase separation (LLPS) and its arrest in protein solutions exhibiting a lower critical solution temperature (LCST) phase behavior using the combination of ultra-small angle X-ray scattering (USAXS) and very-small angle neutron scattering (VSANS). We employ a previously established model system consisting of bovine serum albumin (BSA) solutions with YCl3. We follow the phase transition from sub-second to 104 s upon an off-critical temperature jump. After a temperature jump, the USAXS profiles exhibit a peak that grows in intensity and shifts to lower q values with time. Below 45 °C, the characteristic length scale (ξ) obtained from this scattering peak increases with time with a power of about 1/3 for different sample compositions. This is in good agreement with the theoretical prediction for the intermediate stage of spinodal decomposition where the growth is driven by interface tension. Above 45 °C, ξ follows initially the 1/3 power law growth, then undergoes a significant slowdown, and an arrested state is reached below the denaturation temperature of the protein. This growth kinetics may indicate that the final composition of the protein-rich phase is located close to the high density branch of the LLPS binodal when a kinetically arrested state is reached.

A high-resolution analytical scanning transmission electron microscopy study of the early stages of spinodal decomposition in binary Fe–Cr

Spinodal decomposition (SD) is an important phenomenon in materials science and engineering. For example, it is considered to be responsible for the 475°C embrittlement of stainless steels comprising the bcc (ferrite) or bct (martensite) phases. Structural characterization of the evolving minute nano-scale concentration fluctuations during SD in the Fe–Cr system is, however, a notable challenge, and has mainly been considered accessible via atom probe tomography (APT) and small-angle neutron scattering. The standard tool for nanostructure characterization, viz. transmission electron microscopy (TEM), has only been successfully applied to late stages of SD when embrittlement is already severe. However, we here demonstrate that the structural evolution in the early stages of SD in binary Fe–Cr, and alloys based on the binary, are accessible via analytical scanning TEM. An Fe–36wt% Cr alloy aged at 500°C for 1, 10 and 100h is investigated using an aberration-corrected microscope and it is found that highly coherent and interconnected Cr-rich regions develop. The wavelength of decomposition is rather insensitive to the sample thickness and it is quantified to 2, 3 and 6nm after ageing for 1, 10 and 100h, which is in reasonable agreement with prior APT analysis. The concentration amplitude is more sensitive to the sample thickness and acquisition parameters but the TEM analysis is in good agreement with APT analysis for the longest ageing time. These findings open up for combinatorial TEM studies where both local crystallography and chemistry is required.

Imaging chemical concentration pattern and early stages of spinodal decomposition in the AgxNa1−xBr system by scanning force microscopy

In quasi binary systems like AgBr–NaBr the demixing from the homogeneous high temperature phase into separated phases is a complex process that depends on the ageing temperature as well as on the quench rate. Spinodal decomposition and nucleation processes can be distinguished which lead, however, to the same final equilibrium state. Using frequency modulated scanning force microscopy we aimed to distinguish the demixed phases and their morphologies on a nm-scale at room temperature for samples with different concentration. While no contrast between the different phases are observed in the usual topographic mode, a modified evaluation of Kelvin experiments allows the distinction of silver- and sodium enriched phases. Moreover, direct evidence is found for concentration fluctuations which are characteristic for spinodal decomposition.

Comparison of Monte Carlo and quasi-Monte Carlo technique in structure and relaxing dynamics of polymer in dilute solution

Structure and dynamics of polymer in solvent solution is an important area of research since the functional properties of polymer are largely dependent on the morphology of the polymers in solution. This structure related properties are especially important in case of surface science where the phase-separated morphology in the micro/nano scale dictates the properties of the product. Modeling polymers in solution is an efficient way to determine the morphology and thus the properties of the products. It saves time as well as helps to design novel materials with desired properties. Polymers in solution systems are generally modeled with bead spring model and Monte Carlo or importance sampling Monte Carlo simulations is used to find the optimal configuration where the energy of the system is minimized. Often in these simulations, random numbers are used in the Monte Carlo steps. Normally random numbers try to form clusters and do not cover the entire dimension of the system. Thus the minimum energy structures obtained from simulations with random numbers are not optimal configuration of the system. In the present work a lattice-based model is used for polymer solution system and importance sampling Monte Carlo is used for simulation. Quasi-random numbers generated from Hammersley sequence sampling (HSS) are used in the simulation steps for stochastic selection polymers and its movements. Quasi-random numbers obtained from HSS are random in nature and they have n-dimensional uniformity. They do not form clusters and the structural configuration obtained using quasi-random numbers are optimal in nature. The optimal configurations of the polymers as obtained from random number and quasi-random number are compared. The result shows that simulation with HSS attains a lower energy state after initial quench. At the late stage of spinodal decomposition, the structure factor decrease-showing Ostwald ripening which is not observed from simulation with random numbers.