Precipitate Morphology Research Articles

Effects of heat treatment on the microstructure, mechanical properties and corrosion resistance of AlCoCrFeNiTi0.5 high-entropy alloy

AlCoCrFeNiTi0.5 high-entropy alloy was fabricated, and the effects of heat treatment on the microstructure, mechanical properties and corrosion resistance of this alloy were investigated. The results indicate that heat treatment can not only refine as-cast dendrites and change the morphology of precipitation from long strip to short rod-like structure but also control the ratio of BCC to FCC. The volume fraction of the BCC phase at 1100 °C is 34.8%, which is 9.2% higher than that under the as-cast conditions (25.6%). The highest compression fracture strength and fracture strain of 2785 MPa and 30.7%, respectively, are achieved when the heat treatment temperature and time are 1100 °C and 6 h, respectively. The highest Vickers hardness values of FCC and BCC are 687 HV0.5 and 782 HV0.5, respectively. The order of corrosion resistance is 800-2 h 900-2 h, as-cast, 1000-2 h, 1100-2 h, and 1200-2 h, which is contrary to the trend of the BCC volume fraction. The potential of dendritic FCC is higher than that of interdendritic BCC, and the potential difference is rising because of dendrite decomposition and atom diffusion. The corrosion mechanism is also discussed in this study. Corrosion occurs preferentially on the phase interface and interdendrites, and subsequently connects with each other. As the corrosion intensifies, dendritic FCC begins to be corroded and develops into a large corrosion area.

The Analysis of Dynamic Changes and Prognosis of Posner-Schlossman Syndrome with Cytomegalovirus Infection and Antiviral Therapy.

Purpose To analyze how keratic precipitate (KP) morphology changes during Posner–Schlossman syndrome (PSS) prognosis and raise medication suggestions on 2% ganciclovir eye drops. Materials and Methods Clinical retrospective cohort study in the Eye & ENT Hospital of Fudan University, Shanghai, China. The attacked eyes of 98 eligible subjects diagnosed unilateral PSS were enrolled between 2016 and 2019. All patients were treated with intraocular pressure-lowering drugs and anti-inflammatory steroids. 2% ganciclovir eye drops were given to cytomegalovirus (CMV) immunoglobulin G (IgG) correction ratio positive patients. Frequent follow-ups and examinations were performed. KP morphology was focused and categorized into coin-shaped, mutton-fat, and pigmented. Medical histories were noted. Multidimensional analysis was given. Results Totally 47 patients in 98 achieved all-KP disappearance. Mean treatment time was (5.13 ± 3.66) weeks. Total KP disappearance was negatively correlated with mutton-fat and pigmented KPs at the first visit (P=0.020, P=0.007) and treatment time was also longer (P=0.018, P=0.014). Mean cumulative steroids dosage for 47 subjects was (159.66 ± 161.84) drops. CMV IgG correction ratio positive patients had smaller corneal endothelial cell density (P < 0.005) and larger cup-to-disc ratio (P=0.017) than negative subjects. Cumulative steroid treatment time was longer in the CMV-positive group, and overall dosage was also larger. However, due to 2% ganciclovir eye drops, daily steroid dosage was lower in the CMV-positive group. Conclusions The disappearance of mutton-fat and pigmented KPs needed longer treatment time. Paired aqueous humor and serum CMV IgG tests were recommended in PSS patients with coin-shaped KPs. 2% ganciclovir eye drops improved prognosis; and steroids dosage reduced significantly.

Modelling precipitation hardening in an A356+0.5 wt%Cu cast aluminum alloy

The behavior of a A356+0.5 wt%Cu alloy used to manufacture cylinder heads was studied. Samples were solutionized, quenched and aged at 200 °C for 0.1, 1, 10 and 100 h. TEM characterization showed that for the short aging durations (up to 10 h), the dominating hardening precipitates were β″ rods, while for the long aging duration (100 h), the dominance shifted to the Q-phase (Q′, Q″ precipitates). The length and diameter of the β″ rods were measured to produce size distributions which were later used to calibrate and validate the precipitation model. The physics-based precipitation kinetics model relies on classical nucleation/growth/coarsening equations adapted for the precipitation of Mg–Si precipitates in the aluminum matrix. Indirect coupling to Thermo-Calc software was used in order to determine the essential thermodynamic variables such as the driving force for precipitation and the solubility product for the model. Recent developments regarding the correction of the growth rate equations and the curvature effect were used to take into account the elongated morphology of precipitates. A Kampmann-Wagner Numerical (KWN) based model was used to track the evolution of the size distributions during nucleation, growth and coarsening of the β precipitates. The yield strength of the alloy was modelled using the Pythagorean sum of the contributions of intrinsic strength, solid solution strengthening and precipitation hardening. Both models showed good accuracy when compared to experimental results.

The electrochemistry of ammonium dihydrogen phosphate, disodium phosphate, ammonium chloride on Mg‐based and polycrystalline Pt electrodes

AbstractIn this study, the electrochemical mechanisms of struvite formation were investigated by studying the behavior of Mg‐based and (poly)crystalline‐Pt electrodes in the presence of ammonium dihydrogen phosphate, disodium phosphate, and ammonium chloride solutions. It was found that a precipitate was formed on the Mg‐based electrodes, while the poly‐Pt electrode showed typical voltammetric features in aqueous electrolytes. The structure, morphology, and composition of the electrochemically obtained precipitates collected from the surface of the Mg‐based electrodes were analyzed by scanning electron microscopy (SEM), X‐ray diffraction (XRD), and X‐ray photoelectron spectroscopy (XPS). The results showed that the precipitate morphology was impacted by the composition of the electrolytes and the purity of the magnesium. Moreover, the Tafel kinetics and corrosion rates (vcorr) directly correlated with the electrolyte and the electrode material compositions, whereby both showed a general increase when the Mg‐based electrodes were employed in the presence of chloride anions. The Tafel slopes (β) obtained for the oxygen reduction reaction (ORR) with the poly‐Pt electrode showed a significant difference between the forward and reverse potential scans in the various electrolytes used, a finding which was mainly attributed to the adsorption of hydroxide species, alkali cations, and phosphate anions to the surface whereby these species blocked the ORR active sites.

CALPHAD-informed phase-field modeling of grain boundary microchemistry and precipitation in Al-Zn-Mg-Cu alloys

The grain boundary (GB) microchemistry and precipitation behaviour in high-strength Al-Zn-Mg-Cu alloys has an important influence on their mechanical and electrochemical properties. Simulation of the GB segregation, precipitation, and solute distribution in these alloys requires an accurate description of the thermodynamics and kinetics of this multi-component system. CALPHAD databases have been successfully developed for equilibrium thermodynamic calculations in complex multi-component systems, and in recent years have been combined with diffusion simulations. In this work, we have directly incorporated a CALPHAD database into a phase-field framework, to simulate, with high fidelity, the complex kinetics of the non-equilibrium GB microstructures that develop in these important commercial alloys during heat treatment. In particular, the influence of GB solute segregation, GB diffusion, precipitate number density, and far-field matrix composition, on the growth of a population of GB η-precipitates, was systematically investigated in a model Al-Zn-Mg-Cu alloy of near AA7050 composition. It is shown that the GB solute distribution in the early stages of ageing was highly heterogeneous and strongly affected by the distribution of GB η-precipitates. Significant Mg and Cu GB segregation was predicted to remain during overageing, while Zn was rapidly depleted. This non-trivial GB segregation behaviour markedly influenced the resulting precipitate morphologies, but the overall precipitate transformation kinetics on a GB were relatively unaffected. Furthermore, solute depletion adjacent to the GB was largely determined by Zn and Mg diffusion, which will affect the development of precipitate free zones during the early stages of ageing. The simulation results were compared with scanning transmission electron microscopy and atom probe tomography characterisation of alloys of the similar composition, with good agreement.

Interaction of stress relaxation aging behavior and microstructural evolution in Inconel 718 alloy with different initial stress status

The two-stage aging treatment with different initial loading stresses were carried out in the Inconel 718 alloy after solution annealing process to investigate the stress relaxation and age hardening behaviors on basis of microstructural evolution. The result showed that the stress relaxation behavior mainly occurred in the first aging stage and the corresponding mechanism changed from diffusion creep with initial loading stress of 100 MPa into dislocation slip with initial stress of 600 MPa. Simultaneously, the influence of initial stress on yield strength was counteracted balanced the creep recovery and dislocation hardening, resulting in nearly constant value if yield strength. During the secondary aging stage, the strength of the purely aged sample is 3% higher than that of the high initial stress sample, and the precipitated phase morphology distribution is more uniform. The stress relaxation occurred in the secondary aging stage was negligible, irrespective of initial stress status. In condition, the application of initial stress gave rise to the precipitation behavior, which presented faster growth and coarsening with increasing initial stress value. As a comparison, the distribution of precipitates in sample without loading stress relatively more homogeneous and revealed denser, leading to higher yield strength compared with other samples with initial stress.

Characterization of the nature and morphology of coarse precipitation in various oxide dispersion strengthened steels

Oxide Dispersion Strengthened (ODS) steels are candidate materials for both fission and fusion nuclear reactors. In this study, the microstructure of ferritic (Fe-14Cr-1W) and ferritic / martensitic (Fe-9Cr-1W) ODS steels has been characterized after two different processing routes: Hot Extrusion (HE) and Hot Isostatic Pressing (HIP). Transmission Kikuchi Diffraction (TKD) revealed the presence of Ti-rich precipitates on every specimen. They are identified by X-Ray Diffraction (XRD) as Ti(C,N) and Ti-O (Ti2O3 or TiO2). Intergranular M7C3 and M23C6 have been observed on most Fe-14Cr ODS steels except one, where no Cr-carbides have been found. In Fe-9Cr ODS, intergranular Cr-rich M23C6 carbides have been found. The lack of M7C3 on Fe-9Cr ODS is possibly linked to the matrix phase transformation, not occurring in the Fe-14Cr ODS. Cr-carbides display highly elongated shapes for the Fe-14Cr HE specimens that could be detrimental to the mechanical behavior of the material.

Complex character of the influence of polycarboxylic and phosphonic acids on the crystallization of calcium and magnesium salts in dynamic conditions

The influence of water-soluble organic compounds (adipic, polyaspartic and phosphonic acids) and their compositions on the crystallization of calcium and magnesium salts in dynamic conditions has been studied. It is found that the induction period of phase formation increases in the presence of polyaspartic and phosphonic acids 2.3–5.2 times in the range of their content from 0.05 to 0.2 ppm. The results of XRD and electron microscopic studies confirm the change in the phase composition and morphology of the crystalline precipitate that is formed. The dibasic carboxylic acid influence on the induction period, composition and structure of the precipitate is much less. It is established that the composition of organic acids also increases the induction period of phase formation. The complex inhibitor provides an increase in the critical supersaturation level in the system. The phosphonic and carboxyl groups of the inhibitor interact with calcium and magnesium ions and block the crystallization nuclei. When interacting with the dicarboxylic acid and polyacid adsorption on the surface of the formed crystals, the microcrystals dissolve.

A novel tetragonal precipitate with multiple orientations in Mg–La alloy: An atomic scale investigation using HAADF–STEM

During the process of precipitation in aged magnesium rare earth (Mg–RE) alloys, the subsequent structural transformation of the β″ precipitate is still controversial. In this study, the sequential precipitates of the β″ were investigated in Mg–3.0 wt% La binary alloys by atomic resolution high-angle annular dark-field scanning transmission electron microscopy (HAADF–STEM). Distinguished from the β′, the β″ precipitate in Mg–La alloy is transformed preferentially into a La-rich FCC structure with the two crystallographic orientations to α-Mg matrix, and then evolved into a hitherto unreported tetragonal phase. It is confirmed that the crystal structure of tetragonal precipitate has a symmetry of space group I4/mmm and lattice parameters of a = 0.426 nm and c = 1.080 nm. Meanwhile, there exist three categories of orientation relationships (Type-І, Type-П and Type-Ш) between the tetragonal precipitate and α-Mg matrix in the microstructure. Based on it, the tetragonal precipitate exhibits three typical precipitation morphologies, which are elucidated reasonably according to the interfacial misfit degree. The aim of this study is to provide some efficient subsequent precipitation strengthening phases of β″ precipitate.

Effect of Nb addition on the size and morphology of the \u03b2-Fe precipitates in recycled Al-Si alloys

The recycled Al alloys have a Fe level above the recommended limits, leading to the precipitation of β-Fe intermetallic particles in their microstructure. The brittle β-Fe particles show a rough morphology in the form of highly-faceted platelets, which is detrimental to the alloy's mechanical performance containing these precipitates. This work analyses the possible interactions of the addition of 0–1 wt% of the grain refiner Nb + B to the morphology and size of β-Fe precipitates in alloys melted with Al-(7, 9, 12) wt% Si and 1 wt% Fe. The results indicate that the addition of the Nb + B inoculant revealed a significant change in the precipitates' size and morphology, which have become remarkably refined and spheroidized. Moreover, deepening the study through qualitative and quantitative analyses, it was found that the behaviour of the β-Fe precipitates follows an exponential decay with the increasing addition of Nb + B, a curve analogous to the primary α-Al grain refinement one, revealing a direct correlation between the events. Finally, it was possible to suggest a mechanism that shows how the phenomenon of morphological transformation of the β-Fe precipitates occurs in the material with the addition of the Nb + B inoculant.

The effect of rhenium on the microstructure stability and γ/γ′ interfacial characteristics of Ni-based single crystal superalloys during long-term aging

The effect of 2 wt% Re addition on the microstructure stability and γ/γ′ interfacial characteristics of designed Ni-based single crystal (Ni-SX) superalloys during long-term aging up to 2000 h under 900 °C and 1000 °C was investigated. Re addition significantly affected the γ′ precipitate morphology, γ/γ′ lattice misfit and microstructural stability during long-term aging. Results showed that Re addition significantly enhanced the γ′ precipitates stability: higher volume fraction and smaller coarsening rate. Adding Re delayed the dissolution of the γ′ precipitates at high temperature, suppressed the variation of composition in the γ matrix and attenuated temperature sensitivity of the lattice misfit. Thus, this further reduced the interfacial energy of thermodynamic driving force for coarsening. Through the comparison with available commercial alloys, the Re-containing Ni-SX superalloys possessed minimizing lattice misfit and interfacial energy. More importantly, as the slowest alloying element in terms of diffusion coefficient, Re reduced the effective diffusion coefficient of the alloy, effectively hindering the matrix-diffusion-controlled coarsening of γ′ precipitates. Finally, the γ′ morphological evolution during aging process was discussed, the bifurcation point of the morphological transitions, spheroid-to-cuboid transition and cuboid-to-rod-like transition, were determined based on dimensionless parameter L and shape parameter η.

Development of wax molecular diffusivity correlation suitable for crude oil in wax deposition: Experiments with a cold-finger apparatus

Wax deposition is a hot and difficult topic in waxy crude oil transportation. Wax molecular diffusion is recognized to play a crucial role in wax deposition. Empirical correlations of Hayduk-Minhas and Wilke-Chang are widely used to calculate the wax molecular diffusivity. However, they are developed based on binary solutions and underestimate the diffusion coefficient of wax components. To address this issue, wax deposition experiments with different crude oils were conducted in cold-finger apparatus. The temperature distribution was obtained by computational fluid dynamics software of Fluent and the characteristics of wax deposit were investigated. In addition, the wax molecular diffusion process under saturated and partial saturated conditions were theoretically elucidated. It was found that the bulk temperature, deposition duration and carbon number distribution of wax molecules can significantly influence the total wax content and wax precipitation properties of wax deposits. Moreover, the wax molecular diffusivity experimentally calculated based on the Fick's first law were found larger than that obtained by correlations of Hayduk-Minhas and Wilke-Chang. A new correlation calculating the wax diffusion in crude oil was developed and verified with experiments. Good agreement between predicted and experimental values was observed with maximum relative deviation being 12.52% and mean absolute error being 8.90%. This new correlation is suitable in wax molecular diffusivity calculation for crude oils. • Highly paraffinic crude oils under saturated and partial saturated conditions were used in the wax deposition experiments. • Wax precipitation characteristics and morphologies of the wax deposits were compared and analyzed. • The wax molecular diffusion process was theoretically elucidated and the wax molecular diffusivity was calculated. • A new correlation for predicting wax molecular diffusivity in crude oil was developed and verified with experiments.

Different Response of Cast and 3D-Printed Co-Cr-Mo Alloy to Heat Treatment: A Thorough Microstructure Characterization

The Co-Cr-Mo alloy is a biomaterial with very good corrosion resistance and wear resistance; thus, it is widely applied for knee replacements. The wear resistance is influenced by the amount of hcp phase and morphology of carbidic precipitates, which can both be altered by heat treatment. This study compares a conventional knee replacement manufactured by investment casting with a material prepared by the progressive technology of 3D printing. The first set of results shows a different response of both materials in increasing hardness with annealing at increasing temperatures up to the transformation temperature. Based on these results, solution treatment and subsequent aging at conditions to reach the maximum hardness was applied. Microstructural changes were studied thoroughly by means of optical, scanning electron and transmission electron microscopy. While increased hardness in the conventional material is caused by the precipitation of fine hard carbides combined with an increase in the hcp phase by isothermal transformation, a massive fcc → hcp transformation is the main cause for the hardness increase in the 3D-printed material.

Towards a morphology diagram for terrestrial carbonates: Evaluating the impact of carbonate supersaturation and alginic acid in calcite precipitate morphology

Ancient and recent terrestrial carbonate-precipitating systems are characterised by a heterogeneous array of deposits volumetrically dominated by calcite. In these environments, calcite precipitates display an extraordinary morphological diversity, from single crystal rhombohedral prisms, to blocky crystalline encrustations, or spherulitic to dendritic aggregates. Despite many decades of thorough descriptive and interpretative work on these fabrics, relating calcite micro-morphology with sedimentary hydrogeochemical conditions remains a challenge. Environmental interpretations have been hampered by the fact that calcite morphogenesis results from the complex interaction between different physico-chemical parameters which often act simultaneously (e.g., carbonate mineral supersaturation, Mg/Ca ratio of the parental fluid, organic and inorganic additives). To try to experimentally address the sedimentological causes of calcite morphogenesis, an experimental approach yielding a first attempt at a calcite growth-form phase diagram is presented here. The initial aim was to account for the carbonate products experimentally nucleated in alkaline, saline lake settings. These are the result of at least two competing calcite precipitation ‘driving forces’ that affect morphogenesis: the calcite supersaturation level of the parental fluid, and the concentration of microbial-derived organic molecules (alginic acid). A key finding of this study is that common naturally-occurring calcite products such as calcite floating rafts, rhombohedral prismatic forms, di-pyramid calcite crystals, spherulitic calcite grains, or vertically stacked spheroidal calcite aggregates, can be related to specific hydrogeochemical contexts, and their physical transitions pinpointed in a phase diagram. By exploring binary or ternary responses to forcing in morphological phase-space, links between calcite growth forms and (palaeo)environmental conditions can be determined. This provides a truly process-oriented means of navigating questions around carbonate precipitate morphogenesis for the future.

PVP-assisted Sn-Ti microspheres for the efficient B–V oxidation of cyclohexanone

New Sn-Ti microspheres were first successfully synthesized by a PVP-assisted sol-gel method in this paper, and their performance in the B–V oxidation of cyclohexanone was investigated. The XRD, N2 sorption, SEM, Py-IR, UV–Vis, XPS, EDX, Elemental mapping and TEM characterization techniques were utilized to investigate their physical and chemical properties. Based on the proposal possible formation mechanism, in the MTS-x sample synthesis procedure, the introduction of PVP as a stabilizer and dispersant can coordinate the hydrolysis rate of two different precursors resulting in the hindrance of their agglomerations. And the HDA as a precipitation accelerator and morphology control agent can be beneficial to the formation of spheres by increasing the hydrogen-bonding interactions. The MTS-12 as well as the weight percent of tin to titanium species of 12 with specific regular microspheres has the highest cyclohexanone conversion of 97.8% and the highest e-caprolactone selectivity of 98.2%, which is better than the bulk Sn-TiO2 catalyst even though that the weight percent of tin to titanium species was 18. The catalysts with higher accessible active sites and shorter diffusion channels would provide a valuable theoretic reference for the industrial process of the B–V oxidation of cyclohexanone for the preparation of caprolactone.

Artificial aging time influencing the crack propagation behavior of the aluminum alloy 6060 processed by equal channel angular pressing

The combination of a severe plastic deformation (SPD) by equal-channel angular pressing (ECAP) with a subsequent heat treatment significantly influences the precipitation characteristics of age-hardenable aluminum alloys. The aging kinetics is accelerated and the morphology of the precipitates is affected by the induced strain. In the present study, the influence of the artificial aging time and the resulting precipitation morphology on the fatigue threshold was investigated for the aluminum alloy 6060 with conventional grain size (CG) and after ECAP processing. Four artificial aging conditions are compared for the as-extruded and ECAP processed material, respectively. The resulting microstructure is examined by transmission (TEM) and scanning transmission electron microscopy (STEM) and related to the processing condition and the aging time. The mechanical properties are characterized by tensile and hardness testing and crack propagation tests are conducted in order to determine the threshold ΔKth. The ECAP processed conditions exhibit a lower resistance against crack propagation regardless of the aging time, when compared to the as-extruded conditions. Therefore, the grain size is determined as the major influencing factor on the fatigue threshold. In contrast, the effect of the aging time and the precipitation morphology is only minor. When compared to incoherent precipitates, coherent ones promote planar slip resulting in an increased threshold against crack propagation for both CG and finer grained, bimodal microstructures. However, the size of the coherent precipitates and the resulting lattice distortion is decisive to achieve higher fatigue thresholds.

Compensating Local Magnifications in Atom Probe Tomography for Accurate Analysis of Nano-Sized Precipitates.

Local magnification artifacts in atom probe tomography (APT) caused by multiphase materials with heterogeneous evaporation behavior are a well-known problem. In particular, the analysis of the exact size, shape, and composition of small precipitates is, therefore, not trivial. We performed numerical simulations of APT measurements to predict the reconstructed morphology of precipitates with contrasting evaporation thresholds. Based on a statistical approach that avoids coarse graining, the simulated data are evaluated to develop a model for the calculation of the original size of the precipitates. The model is tested on experimental APT data of precipitates with a higher and lower evaporation field in a ferritic alloy. Accurate sizes, proven by a complementary investigation by transmission electron microscopy, are obtained. We show further, how the size information can be used to obtain compositional information of the smallest precipitates and present a new methodology to determine a correct in-depth scaling of the APT reconstruction in case no complementary geometric information about the specimen exists or if no lattice planes are visible in the reconstruction.

Improved stress corrosion cracking resistance of in-situ TiB2/7050Al composite by pre-precipitation treatment

A two-step aging treatment (50 L P, a peak aging following 50 ℃ pre-precipitation) has been investigated for the in-situ TiB2/7050Al composite. The 50 L P composite has the comparable mechanical properties to the composite at peak-aged (T6) state, and even better stress corrosion cracking resistance over the composite with the retrogression and re-aging (RRA) treatment. In detail, the different aging conditions lead to different precipitate morphologies and grain boundary microchemistries. According to the microstructure characteristics in the Al matrix, the 50 L P composite has considerably increased grain boundary precipitate interspace in comparison with the T6 composite, since the lower aging temperature should result in the reduced grain boundary precipitate number. Furthermore, the 50 L P composite has more Cu content in the grain boundary precipitate and reduced precipitate free zone width over the RRA composite, indicating the improved stress corrosion cracking resistance. For the reinforcement, the TiB2 particles should slightly aggravate the stress corrosion cracking susceptibility, since the grain boundary precipitates are still the preferential corrosion sites due to their lower corrosion potentials.

Effect of Dislocation Networks on Precipitate Morphology in Maraging Steels

We introduce high dislocation densities in a maraging steel using High Pressure Torsion (HPT) processing, followed by ageing them. This gives rise to tensile behaviour substantially different from that of conventional maraging steels. Our Atom Probe Tomography (APT) studies on the steel, show that the morphologies of the Fe-Mo precipitates in such samples with a high density of networks of dislocations is disc-like. Finite element simulations of stress distributions and strain partitioning in such microstructures help explain the reduced macroscopic ductility in them. Using phase field modelling, we show that such morphologies are a result of faster diffusion paths provided by the dislocations. Thus, in addition to providing nucleation sites for precipitation, the faster diffusion paths influence the precipitate morphology and hence the macroscopic mechanical behaviour.

Effect of thermo-mechanical processing on quench-induced precipitates morphology and mechanical properties in high strength AA7075 aluminum alloy

The effect of a novel thermo-mechanical process route on quench-induced precipitates morphology and mechanical properties of high strength AA7075 aluminum alloy is investigated in the present work. After solutionizing the probed material is hot formed and quenched at different tool temperatures ranging from 24 to 350 °C to determine the influence of different cooling rates. The strengthening mechanisms and precipitation morphology after aging are examined based on mechanical testing, microstructure observation and differential scanning calorimetry. The results demonstrate that the tool temperature, as a key element of the investigated process, affects significantly the material strength due to a fundamental change in the microstructure and the strain hardening behavior when exceeding a temperature limit. At tool temperatures from 24 to 200 °C only a slight decrease in tensile strength from 590 to 568 MPa is obtained. When increasing the tool temperature above 200 °C, up to 350 °C, the tensile strength drops to 336 MPa and the initial strain hardening rate θ0 increases. This behavior is linked to the change of quench-induced precipitates morphology and shape. TEM investigations revealed high fractions of semi coherent η’-phases for low and coarse η-phases for high tool temperatures causing a fundamental shift of strengthening mechanisms from predominantly particle shearing to a combination of bypassing and strain hardening by Orowan loops. High diffusion rates and local accumulation of solute atoms at grain boundaries during cooling led to the formation of large grain boundary precipitates during aging, even after high cooling rate using cooled tools.