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There is a lack of information in the literature about the effects of the solidification cooling (Ṫ) and growth (v) rates on both microstructure and mechanical properties of Al-Si-Zn alloys. Moreover, the relation between microstructural parameters and mechanical behavior is valuable information to evaluate the potential of Al-Si-Zn alloys. New applications can be attained when Zn is added to Al-Si alloys, due to the reduction in the liquidus temperature, TL, and improvement in mechanical properties. The present study investigates the evolution of microstructure and the corresponding effects on microhardness of Al-7wt.%Si-(10, 15, 20) wt.%Zn alloys, directionally solidified under unsteady-state conditions. The microstructure of the Al-7%Si-x%Zn alloys is shown to be characterized by a dendritic α-Al matrix, with the interdendritic region composed of α-Al, Si, and an AlFeSi-type intermetallic. The decrease in Ṫ and v resulted in coarsening of the dendrites. Dendritic scaling laws are experimentally determined relating primary, secondary, and tertiary dendritic spacings to Ṫ and v. The main mechanism of reinforcement is shown to be related to the supersaturated solid solution. The hardness of the Al-7%Si-10%Zn alloy is not influenced by refinement of the dendritic spacings, however, each further increment of about 5% Zn to this alloy resulted in a hardness increase of about 30 HV.

Al–10Si–Mg alloy have been used for die casting and additive manufacturing. In this study, solution-treated Al–10Si–Mg and Al–10Si alloys (mass%) were heat-treated at several temperatures and the linear dimensional changes arising from the heat-treatments were investigated. A theoretical model for calculating the linear dimensional change in Al–Si–Mg ternary alloys was proposed, and the theoretically and the experimentally determined linear dimensional changes were compared. It was found that the linear dimensional changes of Al–10Si–Mg and Al–10Si alloys were almost the same. In both alloys, the linear dimensional changes increased with the decrease of the heat-treatment temperature. The linear dimensional changes of Al–10Si–Mg and Al–10Si alloys agreed well with the values estimated by the proposed theoretical model.

Structural and phase transformations in a commercial multicomponent aluminum–lithium alloy have been studied electron-microscopically upon storage after mega-plastic deformation by high-pressure torsion. It has been shown that the arising deformation structure of the alloy is unstable, and upon subsequent storage at room temperature it is transformed via a complex reaction of in situ recrystallization and decomposition of the supersaturated solid solution. The character of the transformation is determined by the regime of the previous mega-plastic deformation and by the duration of the storage.

Solid solutions of Zn as an alloy element in Mg matrixes are expected to show improved corrosion resistance due to the electrode potential being positively shifted. In this study, a supersaturated solid solution of Mg-Zn alloy was achieved using mechanical alloying (MA) combined with laser sintering. In detail, supersaturated solid solution Mg-Zn powders were firstly prepared using MA, as it was able to break through the limit of phase diagram under the action of forced mechanical impact. Then, the alloyed Mg-Zn powders were shaped into parts using laser sintering, during which the limited liquid phase and short cooling time maintained the supersaturated solid solution. The Mg-Zn alloy derived from the as-milled powders for 30 h presented enhanced corrosion potential and consequently a reduced corrosion rate of 0.54 mm/year. Cell toxicity tests confirmed that the Mg-Zn solid solution possessed good cytocompatibility for potential clinical applications. This study offers a new strategy for fabricating Mg-Zn solid solutions using laser sintering with MA.

The microstructures and mechanical properties of Al-3.35Cu-1.2Li-0.4Mg-0.4Zn-0.3Mn-0.1Zr (mass fraction, %) alloy with Sc addition or free Sc were investigated through tensile test, SEM, EPMA and TEM. The addition of 0.082% (mass fraction) Sc element leads to the formation of Cu-rich and Sc-contained nano-sized Al3(ScZr) particles and W phase particles. The Al3(ScZr) particles can inhibit recrystallization to a certain extent and impede recrystallized grain growth during solution treatment. It is found that W phase cannot dissolve in supersaturated solid solution during the solution heat treatment, and the Cu content in the solutionized matrix is decreased, which causes a decrease in the fraction of Cu-contained strengthening precipitates with T1 (Al2CuLi) and θ′ (Al2Cu) under T8 aging condition. Due to the formation of the W phases, the small Sc addition causes a little reduction in the strength.

To elucidate the growth, a kind of non-reversible dimensional change occurring in heat treatments or long-term services, of AlSi10Mg alloy products fabricated by selective laser melting (SLM), the dimensional and microstructural changes arising from a heat treatment at 423 K for 1800 ks were investigated. In as-built state, there were no Si precipitates in the α-Al cells near the top of the specimen and the concentration of the solid solution Si in the α-Al phase was higher than 1.6 wt%. However, some of the supersaturated solid solution Si in the α-Al phase near the bottom of the specimen precipitated during SLM processing. After the heat treatment, the Si precipitates increased in number and coarsened, and the concentration of the solid solution Si in α-Al cells almost became zero. The linear dimensional change arising from the heat treatment was 0.17%, which was much higher than that of gravity cast AlSi10Mg alloy. This linear dimensional change occurred mainly due to the precipitation of the supersaturated solid solution Si in the α-Al phase.

The precipitation kinetics of the GP zones in a supersaturated solid solution depends on the level of its supersaturation which induces a driving force. The magnitude of this driving force increases with the increasing of the undercooling and the increasing of the solute supersaturation. At a given temperature, the increasing of the supersaturation accelerates the precipitation of the GP zones. In an Alxat.%Ag alloy, the transformation kinetics depends on the contribution of the driving force and on that of the thermal activation which is preponderant.

The decomposition of supersaturated solid solution in the Cu–0.06 wt% Zr alloy has been investigated. Upon aging of the initially quenched alloy the homogeneous precipitation of particles is dominating. The decomposition begins from the precipitation of a metastable copper–zirconium phase, the particles of which have the shape of nanodimensional disks. An increase in the aging temperature results in the formation of coarser rodlike particles of the Cu5Zr equilibrium phase. Aging of the deformed alloy is characterized by the predominance of the heterogeneous precipitation of particles at subboundaries and dislocations, and the decomposition begins at a lower temperature. The particle size is less by an order of magnitude than that in the quenched state. The precipitation of nanodimensional particles at dislocations retards the formation of recrystallization centers.

The effect of heavy deformation on precipitation strengthening in a commercially available 6082 alloy was studied. Three levels of deformation were applied to a supersaturated solid solution (including two accumulative roll bonding cycles) followed by artificial ageing at the conventional temperature. The sample with the lowest accumulative strain was the only one that exhibited a strengthening effect. However, the initial examination of deformation induced dislocation structures has shown no differences between various deformation levels. In-situ heating TEM experiments were performed on all specimens to verify the impact of defects on precipitation and the results followed the behaviour of the bulk specimens. Then, dislocation structures were re-examined. It was found that the appearance of dislocation structures depend on the specimen thickness since in the thinnest area of observation dislocation density is significantly reduced in specimens after accumulative roll bonding. The mechanism of precipitates nucleation and further growth is discussed in the light of these observations.

The effect of Mg content on the precipitation behavior and resultant mechanical properties of high Zn-content Al–Zn alloy was studied by adding Mg to Al–20Zn alloy. The dynamic precipitation of Zn and η phases occurred in the Al–Zn–Mg alloys during hot rolling. The Zn phase promoted the precipitation of the η phase, which increased in size with increasing Mg content. Mg addition led to the decomposition of Al–Zn supersaturated solid solution and the precipitation of the η′ phase during natural aging at room temperature. In addition to the η′ phase, the nano-sized Zn phase precipitated in high Zn-content Al–Zn–Mg alloy during artificial aging at 120 °C. The analysis of mechanical properties showed that 0.5 wt% Mg addition can enhance the strength of Al–20Zn alloy after rolling and heat treatments due to the presence of nano-sized η and η′ precipitates. However, when Mg content was increased to 1 wt%, the mechanical properties of the rolled and heat-treated Al–20Zn alloy deteriorated due to the complete decomposition of Al–Zn solid solution and extremely large amount of solute atoms.

α-Al grains surrounded by Al-Si eutectic as the substructures in AlSi10Mg alloy fabricated by selective laser melting (SLM) were investigated in detail using three-dimensional atom-probe and transmission electron microscopy. Quantitative analysis of α-Al revealed (1) the formation of Mg clusters and Mg-Si co-clusters with a density in the order of 1023 /m3 in α-Al of the as-built state caused by the complicated thermal history, and (2) a supersaturated Si content that significantly exceeded the maximum solubility due to rapid solidification, during the SLM process.

CoCrxCuFeMnNi high-entropy alloy powders (HEAPs) with a supersaturated solid solution structure were successfully synthesized via a mechanical alloying technique, and the microstructure and magnetic properties were investigated. After 30 h of milling, one supersaturated solid solution phase with an FCC structure was formed in the CoCuFeMnNi HEAP. The 50 h-ball milled CoCuFeMnNi HEAP had high saturated magnetization (84 emu/g) and low coercivity (6 Oe), indicating that the powder exhibited superior soft magnetic properties. In addition, an asymmetrical displaced hysteresis loop was also observed in the CoCuFeMnNi HEAP, and the shift ΔHs was about 2.3 Oe. When the Cr content increased to 1.5 and 2.0 mol, the structure of HEAPs was composed of FCC and BCC phases. The soft magnetic properties gradually decreased as the Cr content increased because of the decrease in the content of ferromagnetic components and the formation of the BCC phase.

Developing a fast-ageing treatment can significantly reduce the current processing time (180 °C × 9 h) of high strength AA6082 automotive components. In this study, a fast ageing treatment in supersaturated solid solution state was developed, such that the mechanical properties can be rapidly achieved after the paint bake (PB) treatment through introducing a pre-ageing (PA) treatment. The determined fast ageing method considered effects of temperature & time, heating rate and subsequent PB on the ageing response. Tensile tests and TEM observations of typical conditions were undertaken to examine evolved strength and precipitate distribution. Results showed that 210 °C was the optimum pre-ageing temperature as uniformly sized and distributed small precipitates were obtained. The final strength of about 280 MPa, that is 95% of the nominal strength for T6 temper, can be obtained within 15 min soaking for fast heating, and nearly this value for slow heating. More prolific nucleation occurred during slow heating, resulting in more finely distributed precipitates and a higher strengthening. It was observed that PB further increased the strength of over-aged alloy pre-aged at a high temperature of 240 °C. The subsequent PB enabled further nucleation of small clusters and growth of the pre-ageing-induced precipitates which were smaller than 20 nm. This resulted in an improvement in the material strength potentially to satisfy the safety requirements in automotive industry.

A multidisciplinary approach is presented to analyse the precipitation process in a model Al-Cu alloy. Although this topic has been extensively studied in the past, most of the investigations are focussed either on transmission electron microscopy or on thermal analysis of the processes. The information obtained from these techniques cannot, however, provide a coherent picture of all the complex transformations that take place during decomposition of supersaturated solid solution. Thermal analysis, high resolution dilatometry, (high resolution) transmission electron microscopy and density functional calculations are combined to study precipitation kinetics, interfacial energies, and the effect of second phase precipitates on the mechanical strength of the alloy. Data on both the coherent and semi-coherent orientations of the θ ' ' / A l interface are reported for the first time. The combination of the different characterization and modelling techniques provides a detailed picture of the precipitation phenomena that take place during aging and of the different contributions to the strength of the alloy. This strategy can be used to analyse and design more complex alloys.

This paper reports a study on the microstructure and hardness of an as-melt spun Al–Mg alloy as a potential material used for micro-manufacturing. Our results show that the microstructure is characterized by a nearly single-phase fine-grained Al-based supersaturated solid solution containing a relatively high density of dislocations and the as-melt spun Al–Mg alloy exhibits a much higher microhardness relative to that of the coarse-grained counterpart. The quantitative relationship between microhardness and microstructure was established by quantifying the contributions of various strengthening mechanisms.

The effect of severe plastic deformation on the decomposition of supersaturated solid solution has been investigated. A study has been performed on a metastable niobium-titanium alloy (NT-50). It has been established that an increase in the true plastic prestrain of the NT-50 alloy from 4 to 7.6 leads to the significant acceleration of supersaturated solid solution decomposition at all treatment times (from 50 to 2000 h). The volume fraction of the precipitated α-Ti phase increases by ∼(40–50)%. The true prestrain growth brings changes in the mechanisms responsible for the increase in the fracture of the precipitated phase. At the increased true prestrains, the volume fraction of the phase increases with growing sizes of precipitates at a constant and even slight decrease in their density, while at smaller true prestrains, the growth occurs at the expense of the increased number density of the precipitated particles with approximately the same sizes.

The precipitation sequence in Al-Mg-Si alloy is generally accepted as supersaturated solid solution GP-zone β β β (Mg2Si). The effect of Ag or Cu in Al-Mg-Si alloy was reported in our previous work. There is little report about effect of Ag or Cu on the metastable phase and equilibrium phase in this alloy the system. Hexagonal plate like β-phase and Q-phase were observed the Cu added alloy. This hexagonal-shaped β-phase has unique orientation relationship to the Al matrix. This work was performed to compare the shape of effect of the additional elements on the equilibrium phase. The hexagonal shape precipitate was observed in Cu or Ag added alloys aged at 673K.

The quench sensitivity and their influential factors of 7,021, 7,085, and 7,050 alloys were investigated by the end quenching test method and the measurement of electrical conductivity, hardness, and microstructure after aging. The results indicate that 7,050 alloy has the largest changes with hardness decreasing from HV 199 to HV 167, and electrical conductivity increases from 16.6 to 18.2 MS·m−1 when the distance from quenched end increases from 2 to 100 mm. Alloys 7,085 and 7,021 have relatively smaller changes. According to the relationship between the hardness and electrical conductivity of a supersaturated solid solution, 7,050 alloy has higher quench sensitivity than 7,085 and 7,021 alloys. The microstructure of 7,050 alloy with higher major alloy element (Zn + Mg + Cu) addition and Cu element addition is mostly affected by the changes of distance from quenched end. In 7,050 alloy, the size of intragranular precipitates is from about 10–200 nm, and the (sub) grain boundary precipitates are about 20–300 nm. Alloy 7,085 with lower Cu content is moderately affected, while 7,021 is least affected. It is found that with the increase of distance from quenched end, quenched-induced precipitate preferentially nucleates and grows in the (sub) grain boundary and then on the pre-existing Al3Zr particles.

A model based on classical kinetic theory has been developed to predict the evolution of microstructure that occurs on ageing in alloy systems where the supersaturated solid solution decomposes by forming either continuous, discontinuous or mixed precipitate morphologies. The model has been applied to make predictions for the Mg–Al system and explore the interaction between precipitation modes. It predicts that the formation of continuous precipitates inhibits discontinuous precipitation by reducing the supersaturation, which is a far stronger effect than boundary pinning. It is demonstrated that once continuous precipitation becomes established, discontinuous precipitation is effectively suppressed. The reverse is not the case; the formation of discontinuous precipitates only strongly suppresses continuous precipitation when a sufficient volume fraction of discontinuous precipitation occurs to substantially reduce the free volume available for transformation.

The equiatomic multicomponent AlCoCrCuFeNi hexanery high entropy alloy (HEA) was synthesized by mechanical alloying. The effect of the addition of W and Zr was studied by making equiatomic AlCoCrCuFeNiW septenary and AlCoCrCuFeNiWZr octonary high entropy alloys. The effect of alloying addition with milling time was studied using XRD, DSC/TGA, SEM, TEM and Mossbauer spectroscopy. Supersaturated solid solution structure was achieved after 60 h milling for hexanery alloy and after 40 h milling for both septenary and octonary high entropy alloys. The variation of Mossbauer parameters for AlCoCrCuFeNi system with the addition of W and Zr makes its magnetic environment more complex which is indicated by the conversion of magnetic AlCoCrCuFeNi HEA (60 h milling) to partially paramagnetic AlCoCrCuFeNiW (40 h milling) to completely paramagnetic AlCoCrCuFeNiWZr high entropy alloy.

The changes in the structure and properties of the high-strength magnesium alloy IMV7-1 of a Mg-Y-Gd-Zr system are studied after heating at various temperatures. The alloy is hot-worked before annealing to obtain wrought semifinished products. The high stability of a hot-worked structure in annealing is established. It indicates the possibility of using the alloy as a light structural material at elevated (up to 300°C) temperatures. As the annealing temperature increases to 400°C and the holding time is one or two hours, there is only a slight decrease in the hardness, characterizing the strength properties of the alloy. With a further increase in the annealing temperature, a sharp fall in the hardness is observed. Investigation of the structure shows recrystallization in the alloy after annealing at temperatures up to 400°C. After annealing at higher temperatures of 450 and 500°C, the abrupt fall in the hardness is accompanied by complete disappearance of the elongated deformed grains which exist in the hot-worked state and by a significant grain growth. After recrystallization, the alloy retains the ability to be significantly strengthened upon aging, resulting in decomposition of the magnesium-based supersaturated solid solution.

The experiment of laser cladding on the surface of 2Cr13 steel was made. Titanium carbide (TiC) powder and Co-base alloy powder were used as cladding material. The microstructure and property of laser cladding layer were tested. The research showed that laser cladding layer had better properties such as minute crystals, deeper layer, higher hardness and good metallurgical bonding with base metal. The structure of cladding was supersaturated solid solution with dispersed titanium carbide. The average hardness of cladding zone was 660HV0.2. 2Cr13 steel was widely used in the field of turbine blades. Using laser cladding, the good wear layer would greatly increase the useful life of turbine blades.

0.3%Er is added to Al-5.6Zn-1.9Mg-1.6Cu-1.0Li alloy (in wt.%) to investigate the effect of erbium on microstructure of the alloy. Most of erbium exists in the primary Al3Er phases which are incoherent with the alloy matrix unevenly. A few of fine Al3Er phases, precipitated from supersaturated solid solution, are coherent with the matrix. η′-MgZn2precipitates in the single-aged alloy are sparser than that in the double-aged alloy. A few of fine Al3Er phases act as the heterogeneous sites of η phases. There exist some precipitation free zones in the matrix around fine Al3Er precipitates. Erbium is segregated to grain boundary seriously. A few of Al3Er phases are present in grain boundary. The grain boundary precipitates are not continuous about the Al3Er phases.

Cu-Ni-Sn system alloy had been found as high strength by causing the spinodal decomposition of the matrix. Properties of this alloy have been well investigated in the casting process, but not so well in the PM process. Therefore, the sintering and heat treating experiments using each of alloyed and mixed powders of Cu-9mass%Ni-8mass%Sn system carried out to reveal the better condition in the PM process. The results indicated that the sintered compacts using alloyed powder had all homogeneous structures, but those using mixed powder had heterogeneous structure. Furthermore, when sintered compacts using alloyed powder was aged at 623 K for 3.6 ks after sintering, it showed the highest strength with characteristic modulated structure caused by spinodal decomposition. In addition, it was necessary to cool the sintered compacts down to 573 K within 260 s after sintering to obtain supersaturated solid solution avoiding aging during the cooling process.

The N30K10T3 and N40K10T3 invars with the Curie points θC ≈ 200°C and θC ≈ 310°C and the martensite temperatures Ms ≈ −80°C and Ms < −196°C, respectively, have been studied. The two alloys were hardened by quenching in the range of temperatures from 100 to 750°C. In addition, the first alloy was hardened by a combination treatment including phase-transformation-induced hardening and aging. The method of phase hardening consisted in the use of a forward (γ → α) and a reverse (α → γph) martensitic transformations. It has been shown that the temperature dependences of the linear expansion coefficient and the dependences of the hardness on the temperature and time of aging are considerably different for both alloys upon decomposition of the supersaturated solid solution. Both the ordinary and the double aging have been studied.

Amorphization of the Nb&ndash, 20Ti&ndash, 15Si&ndash, 5Cr&ndash, 3Hf&ndash, 3Al (at %) alloy is realized by mechanical alloying (MA). The amorphous phase formation and microstructural evolution are investigated using X-ray diffraction (XRD), transmission electron microscopy (TEM) and scanning electron microscopy (SEM). During ball milling, the phase constituent of the alloy powder exhibits a transition from most supersaturated Nb-based solid solutions (Nbss) and a small amount of amorphous phases (after 20 h of ball milling) to a completely amorphous state (after milling for 40 h), which is accompanied by evolution of the powder morphology from flakes to aggregates and eventually to refined granules. The thermal stability of the milled amorphous powders is studied using differential scanning calorimetry (DSC). With the increase of heating temperature, the distortion energy stored during ball milling is released, followed by a transformation from amorphous phase to Nbss and &gamma, Nb5Si3 phases. In addition, the Vickers microhardness remarkably increases, as a result of the amorphous phase formation in the matrix.

The N30K10T3 invar that has a temperature of the onset of martensite transformation of austenite Ms ≈ −80°C and a Curie point θC ≈ 200°C after water-quenching from 1150°C is studied. The decomposition of a supersaturated solid solution is shown to substantially influence the linear thermal expansion coefficient. The alloy is studied in the following three initial states: after quenching, after phase transformation-induced hardening (γ → αm → γp.h), and after cold (20°C) plastic deformation by 30%.

Heat treatable Al-Mg-Si alloys can be strengthened via the precipitation of metastable phase particles. The precipitation sequence of an Al-0.89Mg-0.75Si alloy with trace Fe and Zn elements during aging at 180 ?C has been investigated by transmission electron microscope (TEM), high resolution transmission electron microscope (HRTEM) and hardness measurements. It has been shown that the precipitation sequence of the alloy can be identified as follows: supersaturated solid solution ? G.P. zones ? metastable ?? precipitates ? metastable ?? precipitates ? stable ? phase + Si particles. It is indicated that ?? phase remains stable up to 30 hours at 180?C. The hardness measurements during aging realize that the main strengthening phase for the investigated Al-Mg-Si alloy is ?? precipitates and the maximum hardness is obtained after aging at 180 ?C for 4~6.5 hours.

The equiatomic multicomponent CoCrFeNiCuAl high-entropy solid solution alloy was synthesized by mechanical alloying (MA). The effects of milling duration and subsequent annealing on the morphology and structure evolution were investigated. Supersaturated solid solution structure can be obtained when the blended powder is ball milled longer than 42 h. The 60 h ball milled alloy powder shows refined morphology and excellent chemical homogeneity. The 60 h ball milled powder exhibits mean particle size of less than 5 μm, which are actually hard agglomerations of nanosized crystalline with crystal size of less than 50 nm. A BCC and a FCC solid solution structure phases appear when the 60 h mechanically alloyed powder was annealed at 600 °C for 1 h, which is attributed to phase precipitation of the metastable supersaturated solid solution. The simple solid solution structure can be maintained even after annealed at 1000 °C.

The glass-forming ability (GFA) of metallic alloys is associated with a topological instability criterion combined with a new parameter based on the average electronegativity difference of an element and its surrounding neighbours. In this model, we assume that during solidification the glassy phase competes directly with the supersaturated solid solution having the lowest topological instability factor for a given composition. This criterion is combined with the average electronegativity difference among the elements in the alloy, which reflects the strength of the liquid. The GFA is successfully correlated with this combined criterion in several binary glass-forming systems.

In the present work the sequence of phases in Al-1%Mg-0.6%Si-1%Cu (in wt %) alloys with 0.4%Sc and 0.2%Zr additions during heat treatment has been studied. The investigated alloys were cast into copper mould to ensure high cooling rate during solidification and the retention of Sc and Zr in the supersaturated solid solution. Two−step preliminary heat treatment was applied: the annealing at temperature 300°C or 350°C followed by quenching from 540°C to water. The precipitation of the Q′ and Al3Sc phases has been observed during the first step of annealing. The annealing at 540°C has led to complete dissolution of the Q′ particles and growth of the spherical particles of the Al3Sc phase. The increase of hardness during subsequent ageing at 165°C (typical ageing temperature of the 6xxx alloys) has been caused by the formation of needle-like Q′ phase which coexist with Al3Sc precipitates.

Phase separations of A1 (γ) supersaturated solid solution into γ, cubic-L12 (γ') and tetragonal-D022 (γ") phases were investigated in Ni-V-Ge alloys by means of transmission electron microscopy (TEM). When Ni-15.8at%V-9.0at%Ge alloy is aged at 1073 K, at the early stage of ageing γ" phases are observed in the γ matrix as triangle- or diamond-shaped precipitates. With further ageing, colonies of lamellar structure consisting of two variants of γ" phase are dispersedly formed in the γ matrix and then γ" plates grow along the direction. When Ni-14.5at%V-8.8.at%Ge alloy is isothermally annealed at 1023 K, first spherical γ' particles precipitate homogeneously in the γ matrix, followed by the formation of lamellar structure of γ" phases. In the course of further ageing, the lamellar structure develops, and only γ' particles around the lamellar structure grow and others gradually fade out.

Microstructure and texture evolution during equal channel angular pressing (ECAP) of Al-5 mass%Ti alloy are investigated for up to 8 passes via routes A and BC. Platelet-shaped Al3Ti particles in the Al-5mass%Ti alloy are cracked severely with repetitive ECAP passes, and the mean size of the Al3Ti particles is decreased with increasing the number of ECAP passes. Microstructural observation showed that an Al–Ti supersaturated solid solution is formed during the ECAP process. It is also found that the Al-Ti alloy after ECAP by route A and route Bc methods have very different microstructures. Namely, after ECAP by route Bc, the fine Al3Ti particles are homogeneously dispersed in Al matrix, while the microstructure has highly anisotropic distribution after ECAP by route A.

Mg–Gd is a promising light hardenable alloy with a high creep resistance at elevated temperatures. The supersaturated solid solution of Gd in Mg decomposes in a sequence of the following phases: �� (D019) → � (c-base centered orthorhombic-c-bco) → (fcc) stable. Formation of the

Kinetics of decomposition of the supersaturated solid solution in the Mg-3.3 wt % Yb alloy has been investigated during aging in a temperature range of 150–225°C using electron microscopy, X-ray diffraction, and hardness measurements. Mechanisms of the decomposition of the supersaturated solid solution and the nature of phases precipitating at different stages of aging, namely, in the underaged, maximum-hardness, and overaged states, have been established. The character of structural components responsible for the hardness changes during aging process has been established.

In the present work a detailed characterisation of a cold rolled and annealed AA3103- alloy has been carried out. The effect of different concentrations of Mn in supersaturated solid solution on the deformation and subsequent annealing behaviour has been studied in detail. A physically based microstructure model has been used to predict the evolution in microstructure and flow stress during annealing of the given alloy, with particular focus on the effect of concurrent precipitation on the softening behaviour.

A Fe-15 atomic percentage Cu mixture was processed by Mechanical Alloying, in a Spex 8000D, and Dynamically Compacted, in a light gas gun. The MA as-powder product was a supersaturated solid solution with a BCC structure (a=0.28736 nm). Nanometric grain sizes between 6 to 30 nm were obtained. Different impact velocities on precompacted cylindrical specimens were used to obtain bulk specimens. The energy used for compaction was between 6 to 10% of the impact energy. XRD and TEM showed no structural changes after DC. We are proposing a Dynamic Compaction Domain in the shock compaction energy vs. ρ 0 /ρ plane, were consolidation of nanometric powders can take place.

By means of differential scanning calorimetry (DSC), the precipitation process from a supersaturated solid solution of Cu–0.65 at.% Co–0.33 at.% Si (Cu–1 at.% Co 2 Si) was investigated. On the basis of enthalpimetric calculations, it was found that the decomposition begins with cobalt precipitation. The clustering of atoms of cobalt initiates the precipitation of silicon, and particles of the stoichiometric Co 2 Si composition are finally formed. Kinetic parameters were obtained by a convolution method based on the Mehl–Johnson–Avrami formalism. Their values are all in agreement with the experimental observed behavior displayed by the DSC traces.

Evolution of the microstructure and mechanical properties of Al–30 wt.% Zn alloy after the severe plastic deformation (SPD) by the high-pressure torsion has been investigated in detail in dependence on the increasing deformation degree. SPD leads to the gradual grain refinement and decomposition of the Al-based supersaturated solid solution. Measurements of the microhardness reveal a successive softening of the alloy with the increased deformation degree.

In the present work, the microstructures and grain refining performance of melt-spun Al–3.5Ti–0.15C, Al–5Ti–0.3C and Al–10Ti–1C (in wt.%) alloys have been investigated, using X-ray diffraction (XRD), scanning electron microscopy (SEM), and grain refining tests. All three types of ingot-like alloys contain coarse slablike TiAl 3 and fine TiC particles. The microstructures of melt-spun Al–3.5Ti–0.15C and Al–5Ti–0.3C alloys are composed of spherical or near-spherical dispersed TiC particles and α-Al supersaturated solid solution, while melt-spun Al–10Ti–1C alloy consists of small blocky TiAl 3 , spherical or near-spherical TiC particles and α-Al solid solution. Furthermore, most of the TiAl 3 and TiC particles are distributed in the edge zone of the chill surface of the rapidly solidified alloy ribbons. Rapid solidification process (RSP) does not improve the grain refinement performance of Al–Ti–C master alloys. The reasons for the formation of microstructures and the grain refining performance of melt-spun Al–Ti–C master alloys have also been discussed.

A Na-modified, as-cast Al-7. wt% Si alloy was processed by equal channel angular pressing (ECAP) up to 8 passes by route A at ambient temperature using a 90° square section die, obtaining improved strength, ductility and work of fracture. From the first pass, porosity is removed, the eutectic constituent is refined and the eutectic silicon particles are partially redistributed. Additionally, a fine and homogeneous strain-induced silicon precipitation occurs in the supersaturated solid solution retained in the casting. These fine precipitates assist in grain refinement, resulting in a 250. nm grain size after one pass and 210. nm after 8 passes. This microstructure cannot sustain grain boundary sliding because it coarsens rapidly even at the lowest testing temperatures. Deformation at high temperatures gives values of n of about 8 and values of the activation energy corresponding to the self-diffusion of aluminum, 142. kJ/mol, which can be rationalized by a constant substructure slip creep mechanism. These values are influenced by the presence and evolution of the fine intradendritic silicon precipitates. Coarsening of these precipitates with time and temperature increases their interparticle distance causing variations in experimental n and Q values. © 2014 Elsevier B.V.

The mechanism of grain refinement in the process of nucleation and growth of cells of discontinuous precipitation in the Pb-5 wt % Sn alloy has been investigated. In the case of the nucleation of cells according to an S-like mechanism, there occurs a “splitting” of the initial grain boundary into three boundaries of two adjacent cells. The boundary between the cells is fixed, the boundaries of the growing cells move into the supersaturated solid solution until the collision with other cells. The possibility of the passage of intercrystallite microcracks into the bulk of grains in the process of the discontinuous precipitation is shown.

The prospects of the use of aluminum — lithium alloys in the aircaft, industry are due to their diminished density and high rigidity as compared to the similar properties of alloys without lithium. This makes it possible to diminish considerably the mass of the structure, which greatly influences the fuel and weight efficiency of the product. The demand for such alloys in aircraft engineering grows steadily. The pioneer alloys of this kind belonged to the Al−Mg−Li system, then came Al−Cu−Li alloys. With the recent creation of alloys in the Al−Li−Cu−Mg system the application range of the alloys has widened substantially. Their main disadvantages include the low adaptability to manufacture and the tendency to embrittlement in the process of long-term operation at a temperature much above room temeprature, for example, in solar heating. The present paper is devoted to the special features of the decomposition of the supersaturated solid solution in a new promising alloy 1470 (Al−Li−Mg−Cu) and the nature of the phases formed. The obtained results have been used for developing practical recommendations for the choice of regimes for reinforcing heat treatment of semiproducts from alloy 1470.

The dendritic growth rate in undercooled, dilute Ti Ni melts was measured by optical means. At a critical value of the undercooling, which is correlated with the difference between the liquidus and the T 0 temperature: Δ T * ≈ 1.5·( T 1 − T 0 ), two Ti-rich alloys with 5 and 10 at.% Ni showed an abrupt increase in the growth rate. In a third Ti-rich alloy with 15 at.% Ni a comparable undercooling level was not reached and only low growth rates were observed. On the other hand a Ni-rich alloy showed only high growth rates of the order of pure nickel. For this alloy the T 0 temperature lies only a few Kelvin below the liquidus, thus a possible jump in the growth rate may be expected in a very low undercooling regime, which was experimentally not accessible. The discontinuous growth behavior can be explained qualitatively by the growth of the supersaturated solid solution phase when the undercooling level exceeds the T 0 temperature by a certain amount. Then the growth mechanism changes abruptly from slow, diffusion-controlled growth to rapid, purely thermally controlled growth of the supersaturated solid solution phase. For diffusionless, purely thermally controlled growth the equilibrium liquidus temperature has to be replaced by the T 0 temperature, the ‘melting’ temperature of the supersaturated solid solution phase. Taking into account some modifications in current dendritic growth theory, basically a modified ‘melting’ temperature, the calculated growth rate fits the experimental data quite well without thermodynamic inconsistency, as is shown for the example of the alloy with 10 at.% Ni.

Amorphization of mechanically alloyed TM-Ta (TM: Fe, Co, Ni) powders was performed in this study. The results indicated that complete amorphization was possible for the composition ranges TM 10 Ta 90 -TM 80 Ta 20 (TM: Ni, Co) and Fe 10 Ta 90 -Fe 70 Ta 30 . The range is larger than for amorphous Ni-Ta alloys prepared by the splat-quenching process and compatible with those of amorphous alloys of Co-Ta and Fe-Ta systems produced by vapor quenching methods, A supersaturated solid solution formed for Co-and Fe-rich compositions. The thermal stability was investigated by differential thermal analysis. The crystallization temperature of amorphous Co-Ta and Ni-Ta powders was found to be proportional to Ta content and higher than those of amorphous alloys produced by rapid cooling techniques.

Cu–14%Fe alloy was produced by vacuum arc remelting and casting in water-cooled mold with subsequent hot extrusion. It had fine grained microstructure with supersaturated solid solutions based on Cu and Fe phases. The alloy was subjected to cold sheet rolling with true strains up to 6.6. Microstructure was studied by SEM and TEM, specific attention was paid to chemical composition of individual phases—copper matrix and iron particles. After rolling very fine lamellar structure formed in copper matrix. Rolling also has resulted in decrease of iron content in matrix from 3.8% in initial condition to 1% after rolling with strain of 5.1 due to decomposition of supersaturated solid solution. At higher strain some deformation-induced mechanical alloying was observed, leading to local increase of iron content. Iron particles also were heavily refined; their average thickness after rolling with strain of 6.6 is about 30 nm (according to TEM data). Several possible mechanisms of their refinement in addition to homogeneous plastic deformation are proposed. Strength of the alloy measured by tensile testing increased significantly after rolling. For example, ultimate tensile strength increased from 325 MPa in initial condition to almost 1000 MPa after rolling with strain of 6.6. Good correlation between mechanical strength and spacing between iron particles in accordance with Hall–Petch relationship was found.

A detailed study of the decomposition process of supersaturated Al-Li-Mg-Cu solid solution was performed during isochronal annealing by means of electrical resistometry and EM. The influence of the phase composition on jerky flow was studied and the conditions for the occurrence of this effect were tested. The concentration of free Li atoms in supersaturated solid solution was shown to have a significant influence on the critical strain for the onset of jerky flow. The temperature limit for the vanishing of jerky flow was also found. Results are compared with a recent model by Kubin and Estrin and Brechet and Estrin.

The supersaturated solid solution (Co x Fe 1 − x ) 20 Cu 80 alloys ( x = 0–1) were prepared by mechanical alloying. The magnetoresistance (MR), magnetic properties and crystal structure of these alloys were investigated. The MR ratio for the (Co x Fe 1 − x ) 20 Cu 80 alloys shows a maximum of 6.4% in the Co 20 Cu 80 alloy ( x = 1), and decreases with decreasing Co concentration. The b.c.c.-Fe and h.c.p.-Co phases disappear after milling for 50 h, and the f.c.c. phase only is observed. The b.c.c. phase is observed for the alloys with a small MR ratio ( x ≤ 0.8), and is the alloy phase of Fe and Co. The b.c.c. phase is not observed for the alloys with a high MR ratio ( x > 0.9).