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Despite the industrial significance of grain size for enhancing mechanical properties and formability, the in-depth deformation mechanisms at elevated temperature are still unclear. To investigate the functions of grain size on hot workability and deformation mechanisms, three groups of Mg-1.2Zn-0.2Y alloy specimens with different grain sizes were hot compressed and then studied by combining constitutive model, processing map and microstructural observations. The results showed that the enhanced hot workability accompanying low deformation activation energy and small instability regime was obtained with refined grain size. During hot deformation, the decreased grain size in Mg-1.2Zn-0.2Y alloy mainly improved the plastic deformation homogeneity, especially for the weakened local straining around grain boundaries. As a result, the dynamic recrystallization nucleation and texture development at lower strain level were influenced by the initial grain size. At higher strain magnitude, the growth and coarsening of dynamic recrystallized grains would further release strain localization and improve hot workability, while the texture was less impacted. Further, unlike the primary basal slip and deformation twinning in the specimen with coarse grain at low temperature, non-basal slips of dislocations were initiated with less deformation twins in the specimens with refined grain size.

The metastable α' phase and dislocation characteristics (e.g., density and constituents) are of vital importance for the mechanical responses of (α+β) titanium alloys. In this work, to reveal the in-depth decomposition mechanisms of dislocations and metastable α' and their influences on mechanical properties in a Ti-6Al-4V (α+β) alloy, the thermal stability of different microstructures tailored by various cooling approaches were investigated utilizing scanning electron microscope, electron backscattered diffraction, transmission electron microscope and X-ray diffraction line profile analysis. The results showed that the initial characteristics of α' and α laths and dislocation density were influenced by the cooling methods remarkably. The thermal stability of Ti-6Al-4V alloy increased with decreasing cooling rate. The improvement in thermal stability can be ascribed by the decrement in dislocations, partitioning of the alloying elements and grain orientations variation of the α' lath and α phase. It is also found that the plastic strain accommodation of β→α' transformation was dominated by dislocations. During stabilization annealing treatments, the , and dislocations simultaneously decomposed. The decomposition of dislocations and metastable α' phase during various stabilization annealing and the particular twins and stacking faults microstructures formed during quenching have a great influence on the properties of the studied Ti-6Al-4V alloy.

In the present work, a double-pass continuous expansion extrusion forming (CEEF) process was proposed for an Al-Mg-Si alloy, in which the diameter of rods was gradually expanded. The microstructural evolution, mechanical properties and deformation characteristics were investigated by utilizing microstructural observations, mechanical testing and a finite element method coupled with a cellular automata model. The results showed that the strength and ductility of the double-pass CEEF processed Al-Mg-Si alloys were improved synchronously, especially in artificially aged alloys. The grain size of the processed Al-Mg-Si alloy rods was refined remarkably by continuous dynamic recrystallization (CDRX) and geometric dynamic recrystallization (GDRX), and the homogeneity of microstructure was gradually improved with increasing number of processing passes. The artificially aged alloy processed with double-pass CEEF and water quenching contained fine (sub)grains and high-density dislocations, which resulted in more needle-shaped β” precipitates and a larger precipitate aspect ratio than the as-received and air-cooled CEEF alloys owing to the different precipitation kinetics. The severe cumulate strain and microshear bands were found to accelerate CDRX and GDRX for grain refinement between adjacent positions of the parabolic metal flow due to the special temperature characteristics and large shear straining during the CEEF process.

The precipitation evolutions of Mg-Al-Zn alloys play essential roles in their mechanical properties, corrosion performance, formability, plastic deformation mechanisms and texture development. In the present work, the precipitation evolutions of AZ80 magnesium alloy during both non-isothermal and isothermal processes were unraveled by utilizing in situ electrical resistivity monitoring, hardness testing, differential scanning calorimetry and microstructural characterization. The results showed that discontinuous precipitation (DP) and continuous precipitation (CP) occurred competitively during non-isothermal and isothermal processes. The precipitation of dominant β-Mg17Al12 phase during non-isothermal processes was highly dependent on the thermal history. During isothermal processes, the precipitation behavior of AZ80 magnesium alloy could be considered as the functions of holding temperature and time. At lower temperatures, massive DP and CP were gradually formed to equally strengthen the alloy. At higher temperatures, the Ostwald coarsening was characterized in the later stages and indicated to slightly soften the alloy. Isothermal time-temperature-precipitation curves and quantitative precipitate evolution were estimated to unravel precipitation characteristics and their strengthening functions.

The flow softening is an important phenomenon during hot deformation of metallic materials. In the present work, a more evident flow softening of Ti-6Al-4V alloy when deformed in two-phase region was observed in coarser α grain sample, which was attributed to an accelerated dynamic transformation from harder α phase into β phases. Notably, full β microstructure was observed in coarse grain samples at strain of 1.2, while retained α phase was observed in fine α grain specimens. In the views of thermodynamics and crystallographic analysis, the in-depth mechanisms of dynamic transformation were further investigated.

In the present study, the effects of strain paths (i.e., single-pass and multi-pass hot compression) on microstructural and texture evolutions of AZ80 magnesium alloy were studied at temperature of 350 °C and strain rate of 0.01 s−1. The results showed that flow stresses are remarkably dependence on strain path changes. Flow stress hardening phenomenon during interrupted holding of multi-pass hot deformation was observed, which led to higher peak stress of next pass than previous unloading stress. Strain paths presented slight influence on grain size. Significant contribution of strain paths to texture evolution was found. Due to dynamic recrystallization and meta-dynamic recrystallization, texture components gradually changed from ( 1 ¯ 2 1 ¯ 0 ) and ( 01 1 ¯ 0 ) in single-pass deformation to (0001) 01 1 ¯ 0 > and (0001) 11 2 ¯ 0 > in four-pass deformation. The observed flow stress hardening phenomena were interpreted by the combined functions of grain coarsening and texture evolution.

Zn content has significant influence on the hot workability and final properties of Al–Zn–Mg–Cu alloys. In the present work, single and double stage hot compression tests have been performed on Al–Zn–Mg–Cu alloys with various Zn contents at temperatures of 300 °C and 400 °C, and strain rates of 0.01 s−1 and 0.1 s−1, respectively. The results showed that the static softening curve plateau was observed, both the duration of static softening plateau and softening fraction decreased with increasing Zn content at deformation temperature of 300 °C. When deformation temperature increased to 400 °C, the static softening curves appeared approximate typical sigmoidal shape with slight influence from Zn content. By combining additional in-situ electrical resistivity measurement, hardness testing and microstructural observations, the static softening mechanisms were found to be the functions of static recovery and precipitates coarsening at lower temperature, and static recovery and static recrystallization at higher temperature. The increased Zn addition mainly affected static softening mechanisms at 300 °C by forming precipitates. The simplified static softening kinetics were also investigated based on Johnson-Mehl-Avrami-Kolmogorov model which coupling static recovery and static recrystallization.

Double-stage interrupted uniaxial hot compression tests were conducted to investigate the static softening behavior in Al-Zn-Mg-Cu alloys with various Zr additions at temperature of 300 °C and 400 °C and strain rates of 0.01 s−1 and 0.1 s−1. The microstructural evolution was also characterized by utilizing electron backscatter diffraction and transmission electron microscopy. The results revealed that static softening fraction of the studied alloys increases with increased Zr additions. Different static softening kinetics and plateaus were indicated to be the functions of deformation temperature, strain rate and Zr addition. At 300 °C, the observed short static softening plateaus were attributed to static recovery, static precipitation and its coarsening during post-deformation holding. High static softening fractions and long plateaus were presented when deformed at 400 °C and 0.1 s−1, which were resulted from rapid static recovery and recrystallization within very short time.

Hot workability, which indicates the ability of metallic materials to be deformed at elevated temperatures, is generally governed by the microstructure-dependent strength and ductility. In this work, the influence of three types of pre-precipitation microstructure, tailored through different cooling conditions (i.e., air cooling, water quenching and furnace cooling) after heat treatment, on hot workability in an Al-Cu-Mg-Zr alloy was studied by means of constitutive analysis, processing maps and microstructure characterizations using scanning electron microscopy, electron backscatter diffraction and transmission electron microscopy. The results showed that pre-precipitation microstructure had a considerable influence on flow stress, hot deformation activation energy, dynamic softening and hot workability. The highest flow stress accompanied by a more notable dynamic softening was shown in the water-quenched alloy, whereas the flow stress in the furnace-cooled alloy was the lowest. The flow stresses of air-cooled, water-quenched and furnace-cooled alloys could be described well by the hyperbolic sine equation with hot deformation activation energies of 180.5, 298.9 and 161.5 kJ/mol, respectively. Dynamic softening mechanisms were found to be associated with different contributions of dynamic recovery, dynamic precipitation and/or dynamic recrystallization in various tempers of the present alloy. Further, the air-cooled alloy showed minimal instability regimes and an optimal pre-precipitation microstructure for hot forming. The deteriorated hot workability in the water-quenched alloy was attributed to dynamic precipitation effects. However, coarse constituent phases in the furnace-cooled alloy were easily broken during deformation under a higher strain rate, which led to deformation instability.

A novel repetitive continuous welding extrusion process was proposed to optimize the microstructure and mechanical properties of AZ31 magnesium alloy. Both strength and elongation were improved simultaneously after two passes extrusion processing owing to the effective grain refinement and basal texture modification by introducing additive severe shear deformation.

Plastic lattice strain anisotropy in polycrystalline aggregates involves complicated integration of single crystal elastic anisotropy, grain-grain interactions and orientation-dependent slip activations. It is essential to experimentally determine plastic lattice strain anisotropy for in-depth understanding elasto-plastic deformation mechanisms and rationalizing advanced models. Unlike the widely applied method for quantifying elastic lattice strain anisotropy utilizing diffraction peak shift, accurately evaluating plastic lattice strain anisotropy is still enormously challenging over the decades. In this work, we developed a new diffraction line profile breadth analysis approach to reliably assessing plastic lattice strain anisotropy based on the simple linear dependence in quasi elasto-plastic model. The approach is confirmed to be effective and adaptive in practical application by linearization of the experimental dependences for line profile broadening in nickel under various cold-working strain paths. Then the orientation-dependent plastic lattice strain values could be reliably estimated up to high strain levels, which were identical to the magnitude of published elastic lattice strain. The strain levels and strain paths dependent plastic anisotropy magnitude was also inferred and further compared with the results from classical elastic models, i.e., Reuss, Voigt, Reuss-Voigt average and Eshelby-Kroner models. Simultaneously, by further carrying out microstructural characterization and dislocation model based line profile analysis, correlative texture and dislocation (arrangement and edge/screw constituent) developments were found to be strongly depended on strain paths, as well as verified to be the primary contributions to strain anisotropy. In addition to the proposed explanations in two-phase composite model, the strain hardening was demonstrated to be impacted by strain anisotropy behaviors as well. The fundamental mechanisms and significance of above interrelated effects under various strain paths were also well discussed.

The microstructural evolutions and resulted mechanical responses during isothermal holding of multipass hot deformation are essential aspects in the processing of high performance titanium alloys. In this work, isothermal holding testing was performed on a Ti-5Al-3V alloy after hot compression at temperatures of 900 °C, 930 °C and 960 °C, respectively. Stress relaxation, dilatometer measurements, and microstructure examinations (i.e. scanning electron microscope, electron backscatter diffraction and transmission electron microscope) were employed to investigate the phase transformation behaviors. The results showed a flow stress hardening phenomenon during the interrupted isothermal holding in two phase region. The post-dynamic transformation from α to β phase took place first during the early stage of isothermal holding after hot deformation. With longer isothermal holding time, the reverse transformation of meta-stable β phase to α phase was then observed. Under TEM, the reverse transformed α phases were isolated from quenched α' phases. The in-depth mechanisms of post-dynamic α to β phase transformation and reverse transformation were discussed as well. Keywords: Titanium alloys, Phase transformation, Hot deformation, Microstructure

Multistage stress–strain curve correction based on an instantaneous friction factor was studied for axisymmetric uniaxial hot compression of 7150 aluminum alloy. Experimental friction factors were calculated based on continuous isothermal axisymmetric uniaxial compression tests at various deformation parameters. Then, an instantaneous friction factor equation was fitted by mathematic analysis. After verification by comparing single-pass flow stress correction with traditional average friction factor correction, the instantaneous friction factor equation was applied to correct multistage stress–strain curves. The corrected results were reasonable and validated by multistage relative softening calculations. This research provides a broad potential for implementing axisymmetric uniaxial compression in multistage physical simulations and friction optimization in finite element analysis.

The precipitation kinetics and its effect on hot working behavior of an Al–Zn–Mg–Cu alloy were studied under non-isothermal conditions and over a wide range of temperatures. The characterization techniques employed included in situ electrical resistivity measurements, differential scanning calorimetry, hardness testing and microstructure examination by scanning and transmission electron microscopy. The results showed that the precipitation kinetics during non-isothermal treatments were highly dependent on the thermal paths. Slow cooling processes led to coarse and sparse particle distribution. When heating to high temperatures, very fine precipitates with high density and homogeneous distribution were present at low temperature. Such fine precipitates showed unstable characters and dissolved quickly at higher temperature. Quantification of precipitate evolution during non-isothermal processing was obtained from in situ electrical resistivity measurements. The effects of heating paths on dynamic and static flow behaviors were also demonstrated to be significant. The degree of initial supersaturation controlled the nucleation rates and led to strong effect on dynamic and static precipitation, and on the flow stress softening.

Repetitive continuous extrusion forming was employed as a continuous severe plastic deformation route and both Al-Fe-Cu alloy and Al-Mg-Si alloy were involved. Evolution of microstructures and properties during this process is investigated by optical microscope, electron-backscatter diffraction, transmission electron microscope, and tensile testing. The results show that in the Al-Fe-Cu alloy an obvious mechanical softening and grain refinement were observed, while in the Al-Mg-Si alloy it shows a slightly rising in strength and ductility as the extrusion passes increasing.

High-speed repetitive continuous extrusion forming process (R-Conform process) was performed on the Al-Fe-Cu alloy. The microstructural evolution and mechanical properties were studied by x-ray diffraction, electron backscatter diffraction, transmission electron microscopy and tensile testing. The results show that a significant improvement of tensile ductility concurs with a considerable loss of tensile strength before four passes, after that the process on mechanical properties variation tends to be steady, indicating an accelerated mechanical softening occurs when comparing to low-speed R-Conform process. Microstructure characterization indicates that the accumulated strain promotes the transformation of low angle boundaries to high angle boundaries, thus leading to the acceleration of continuous dynamic recrystallization process, and the precipitates are broken, spheroidized and homogeneously distribute in Al matrix as increasing R-Conform passes. Massive microshear bands are observed after initial passes of R-Conform process, which may promote continuous dynamic recrystallization and further grain refinement during high-speed R-Conform process.

In situ electrical resistivity monitoring technique was employed to continuously evaluate the precipitate evolution of an Al–Zn–Mg–Cu-based commercial alloy during typical artificial aging treatments. The effects of artificial aging on the precipitates stability during non-isothermal heat treatments were also explored. Conventional hardness test, transmission electron microscopy and differential scanning calorimetry were also adopted to verify the electrical resistivity results. The results indicated that both the precipitation process and its timely rate could be followed by the monitored electrical resistivity during artificial aging treatments. The electrical resistivity results gave overall information on continuous precipitation and dissolution processes, especially under high heating rates. Samples artificial aging heat treated at 120 °C for 24 h followed by aging at 150 °C for 24 h presented more stable state and coarser precipitates than the samples only artificial aging heat treated at 120 °C for 24 h or triple artificial aging heat treated at 120 °C/24 h + 195 °C/15 min + 120 °/24 h. While the incoherent η precipitates in the samples artificial aging heat treated at 120 °C for 24 h followed by aging at 150 °C for 24 h were more easiness to coarsening and dissolve during non-isothermal heat treatments as well.

Hybrid aluminum matrix composites are appealing in the aviation, aerospace and automotive industries and have the potential to substitute single reinforced composites due to their enhanced comprehensive properties. In the present work, 6061 Al matrix composite hybrids reinforced with SiC and stainless steel particles were prepared to improve the strength and ductility by the powder metallurgy method. The mechanical properties, fracture behaviors and deformation mechanisms under various aging conditions were investigated by uniaxial tensile tests and microstructural characterizations. The results showed that the composite hybrid reinforced with SiC and stainless steel particles could effectively enhance the ductility without losing strength compared to the composite reinforced with single SiC particles. Under various artificial aging treatments, the mechanical properties of the composites changed, but the stainless steel particles always played a positive role in the composites and did not change the precipitation sequence of the aluminum matrix. The improvement in ductility was mainly attributed to the deformable nature of the reinforcement particles. The load was successfully transferred to the stainless steel particles and resulted in a uniform strain distribution of the hybrid reinforced composites. Conversely, the interfacial fracture caused by high interfacial dislocation pileup during deformation limited the plasticity of aluminum matrix composites reinforced with single SiC particles.

Modern aluminum industries need an in-depth understanding and a more accurate prediction of the flow stress and microstructure evolution during multi-stage thermomechanical processing. The underlying mechanisms of Al alloys are distinct from that of other metallic materials (e.g., steels and copper) owing to the very high stacking fault energy. In the hot forming process of ultra-high strength Al-Zn-Mg-Cu alloys, the high alloying element additions have a more complex effect on multiple static softening mechanisms during post-deformation, i.e. the coupled recovery, recrystallization, precipitation and their interactions, which have not been well revealed and included in the existing plasticity models. In the present work, an integrated physically based model based on the observed microstructural characteristics and static softening behavior was developed to unravel the multiple static softening mechanisms following multi-stage hot deformation of Al-Zn-Mg-Cu alloys. By incorporating the multicomponent effects, i.e. process variables and chemical compositions, into static recovery, static recrystallization and precipitate coarsening models, the evolutions of stress, microstructure and static softening fraction could be accounted reasonably during post-deformation holding. A special attention was paid to model the functions of various alloy solute contents (i.e. Zn, Mg, Cu and Zr) on the precipitation thermodynamic, recovery and recrystallization kinetics in Al-Zn-Mg-Cu alloys. After validating by experimental data, the integrated physically based model could predict the effects of alloying elements on microstructural evolution, recrystallization and static softening kinetics of Al-Zn-Mg-Cu alloys. It was found that the different precipitation behaviors due to the addition of various alloying elements have a considerable influence on recovery, recrystallization and coupled static softening process. The solid solution atoms remaining in the matrix basically contributed to grain boundaries mobility and then slow recrystallization process, which depended on the interaction parameter, binding energy and diffusion rates of various alloying elements. This work offers an in-depth understanding of static softening mechanisms and provides a potential way for future development of advanced models and design strategies for multi-stage thermomechanical processes in Al-Zn-Mg-Cu alloys.

Strong metals are greatly desired for lightweight and energy-efficient industrial design. The strengthening of metals is traditionally accomplished by the additive contributions of various obstacle families (e.g., solid solutions, particles, and grain boundaries) and dislocation self-interactions that impede dislocation motion. In the present work, unlike a traditional additive understanding, a distinctive nonadditive strengthening mixture rule for obstacles and dislocations were validated based on experimental and modeling analyses in numerous cold-worked steels and aluminum alloys. Concretely, numerous well-annealed body-centered cubic steels and face-centered cubic aluminum alloys were prepared, in which the hierarchical strength levels of solid solutions, grain boundaries, and/or particles were estimated. The above specimens were then cold rolled to various strain levels. Dislocation densities were quantified by utilizing X-ray diffraction line-profile-analysis, and the dislocation density was found to increase faster with an increasing strain level when a high strength was presented in well-annealed specimens. When plotting the yield stresses as a function of the square roots of the dislocation densities in massive distorted samples based on the Taylor hardening law, it is interesting to note that an approximate single linearity was obtained. Individual dislocation strengthening was found to respond to the total strength in the deformed specimens, which indicated that the full nonadditive strengthening mixture rule was employed between the obstacle families and the dislocation contributions. The mechanisms of the observed nonadditive strengthening were also discussed by implementing additional experiments and transmission electron microscopy observations. Then, the modified constitutive models based on both one and two internal parameters’ Knocks-Mecking models were developed respectively, which excellently captured the effects of the various obstacle families on dislocation storage processes. The developed models also rationalized the observed nonadditive strengthening mixture rule.

The complex precipitates have been found to work on the hot workability of heat treatable Al alloys considerably. In this work, to include the functions of interrupted holding following multistage hot working, double-stage hot compression tests were performed on an Al–Cu–Mg–Zr alloy with different pre-precipitation microstructures which were tailored through air cooling, water quenching and furnace cooling after solution heat treatment. Microstructural characterizations and physically-based modeling were employed to investigate the static softening behaviors during interval holding. The results indicated that static softening fraction increased with rising deformation temperature, strain rate and holding time. Under the same deformation conditions, the furnace-cooled alloy presented the highest static softening, while the lowest in water-quenched alloy. Particularly, double plateaus were presented in the static softening curve of water-quenched alloy when deformed at 300 °C and 0.1 s−1, which was interpreted by static recovery, static precipitation and its coarsening as well as the complete depletion of stored strain energy during post-deformation holding. When deformed at 450 °C and 0.1 s−1, higher static softening fraction and longer plateaus were observed in all alloy specimens due to the remarkable static recovery within a very short holding time after first-pass deformation. In addition, the established recovery model could generally rationalize the experimental results, and the direct static softening contribution of precipitates coarsening was indicated to be slight according to the results of integrated model.

Al–Mg–Si alloy overhead conductor was prepared by horizontal continuous casting and subsequent continuous extrusion forming. The mechanical properties, electrical conductivity and microstructural evolution of the processed conductor were characterized. It was indicated that improved combined mechanical and electrical conductivity properties were obtained for the processed alloy wires when compared with previously reported results. The enhanced properties were associated with the continuous in-line solution treatment and the refined and homogeneous (sub)grains during horizontal continuous casting and subsequence continuous extrusion forming, as well as a high density of dislocations and finer Mg 2 Si precipitates formed after drawn and followed by aging at 155 °C for 3 h.

Isothermal and non-isothermal multistage hot compression tests were carried out on 7150 aluminum alloy at temperature range of 325–425 °C and strain rate range of 0.01−1 s−1. During isothermal multistage hot compression, the flow stress decreased with increasing temperature, accumulative strain as well as decreasing strain rate and pass strain. However, the interval time had a complex influence on flow stress, which ascended flow stress values with increasing interval time at 425 °C. The isothermal and non-isothermal constitutive characteristics were studied based on hyperbolic-sine law, indicating complex influences of various processing parameters on material constants. Non-isothermal multistage flow stresses were found to be easier than normal continuous single pass method to manipulate for constitutive equations calculation with better linear fitting reference and comparable activation energy. Precipitation at low temperature and its dissolution at high temperature were found to affect flow behavior and constitutive characteristics remarkably based on microstructural observation of deformed sample.

The hot deformation characters of two Al–Mn–Mg–RE alloys (without and with Ti addition, respectively) were studied by hot compression tests, and the deformed microstructures were observed by optical microscopy and transmission electron microscopy, respectively. The results show that the flow stress, hot deformation activation energy and stress exponent were higher with the addition of Ti during hot deformation. Less indistinct subgrain boundaries were also obtained with addition of Ti. The main enriched rare earth constituent particles could make positive purifying effects on impurity elements of Fe and Si in the Al–Mn–Mg–RE alloy. While the addition of Ti not only promoted the formation of a more stable Ti 2 Al 20 (Ce x , La 1− x ) phase, but also resulted in more refined and dispersive constituent particles, which could improve the hot workability of the alloy.

Hot compression tests of the horizontal continuous casting Al–0.96Mn–0.38Si–0.18Fe alloy were preformed on Gleeble-1500 system in the temperature range from 350 °C to 500 °C and at strain rate range from 0.01 s −1 to 10 s −1 , and the associated microstructural changes were studied by the observations of optical metallographic and transmission electron microscope. The results show that the flow stress below 450 °C and at higher strain rates increases with increasing strain and tends to be constant after a peak value, showing a steady state flow until high strains. While above 450 °C and at lower strain rates, the flow stress reaches a plateau and then decline slightly, showing a flow softening. The peak stress level decreases with increasing deformation temperature and decreasing strain rate, which can be represented by a Zener–Hollomon parameter in the hyperbolic-sine equation with the hot deformation activation energy of 159.24 kJ/mol. The steady state flow results from dynamic recovery whereas flow softening is associated with dynamic recrystallization and dynamic transformation of precipitates. The designed columnar coarse grains were capable of GDRX above 450 °C and at lower strain rates.

Isothermal continuous and interrupted hot compression tests have been carried out on Gleeble-1500 system at temperatures of 300 °C and 400 °C, strain rates of 0.01 s −1 and 0.1 s −1 , respectively. The dynamic and static softening kinetics of 7150 aluminum alloy during multistage hot deformation were investigated by means of flow curves and relative softening rates. The results show that the flow curve exhibits a peak and some work softening during hot deformation of 7150 aluminum alloy. The flow stress increased with increasing strain rate and decreasing temperature while the flow softening decreased. The static softening increased with increasing strain rate, deformation temperature and delay time. The static softening curves appeared as a typical sigmoidal shape of the type at temperature of 400 °C, while plateaus were observed when temperature decreased to 300 °C. The appearance of static softening at 400 °C exceeding 100% was observed. An empirical static recrystallization model based on Johnson–Mehl–Avrami–Kolmogorov model with the recrystallization activation energy of 219.17 kJ/mol for 7150 aluminum alloy was derived.