Metastable Solid Solution Research Articles

The effect of SiC particles on thermal shock behavior of Al 2O 3/8YSZ coatings fabricated by atmospheric plasma spraying

This paper reports studies into the effect of SiC particles on thermal shock resistance of Al 2O 3–20 wt.% 8YSZ coatings fabricated by air plasma spraying. Six kinds of coatings were prepared from nanostructured agglomerated feedstocks. The unmelted particles, molten droplets, voids and microcracks were observed in the ceramic coating. The Al 2O 3/8YSZ coating significantly cracks on the surfaces compared with the coatings containing SiC. The thermal shock test for ceramic coatings was carried out by water quenching method. The metastable phase, solid solution and silicate fibers are formed after plasma spraying and thermal shock cycling. Testing results show that the submicron SiC (average particle size is 3 μm) particles are beneficial to the thermal shock resistance of Al 2O 3/8YSZ coatings with thermal shock cycles of 198 and 216 at 800 °C, but the nano SiC (average particle size is 70 nm) particles are not. The thermal shock resistance of Al 2O 3/8YSZ coatings is increased greatly from 5 to 83 cycles with addition of SiC particles at 1000 °C. The damage process and failure mechanism for the ceramic coatings are different at different thermal shock temperatures. Some silicate fibers were formed on the coating surface and through thickness after thermal shock. The Al 2O 3·xSiO 2 silicate fibers can greatly increase the thermal shock resistance of ceramic coatings. The thermodynamic condition for generating silicate fibers was calculated and analyzed. The failure mechanism, which was investigated and analyzed in terms of microcracks, splat lamellae, formation of debris and silicate fibers, is tilting, spallation, interface delamination and fracture.

Relaxation scenarios in Fe–Pd and Fe–Pd–Cu ferromagnetic shape memory splats: Short range order and microstructure

Fe–Pd-based ferromagnetic shape memory alloys are based on metastable random solid solutions in the austenite and martensite phases, which require preparation from the equilibrium γ phase by rapid cooling. Employing splats, we explore the impact of annealing treatment on the disordered solid solution, phase formation and lattice defects using a combined conversion electron Mossbauer spectroscopy – X-ray diffraction study. We discuss indications of short range ordering tendencies as well as the impact of splat microstructure and defects on phase formation.

Phase Evolution in the Fe$_{3}$O$_{4}$–Fe$_{2}$TiO$_{4}$ Pseudo-Binary System and Its Implications for Remanent Magnetization in Martian Minerals

Titanomagnetites offer a rich system to explore the role of fine microstructure on magnetic properties. They are important minerals in basalts, and are commonly found on the moon and Mars. Here magnetic measurements were used to monitor decomposition and phase evolution in the pseudo-binary Fe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> TiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> -Fe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> solid solution system. The phases appearing in the decomposition are a strongly magnetic magnetite and a weakly magnetic Ti-rich spinel. For the 40, 50, and 60 at% Fe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> TiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> compounds (balance Fe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> ) explored here, a metastable solid solution is nonmagnetic at temperatures where decomposition kinetics can be monitored in reasonable experimental times. The magnetization of magnetite formed by the decomposition offers a direct measure of the volume fraction transformed. Time-dependent magnetization measurements were used to monitor the kinetics of decomposition and compared to models for spinodal decomposition and nucleation and growth kinetics for compositions outside the spinodes. The fine microstructure resulting from spinodal decomposition and exchange bias mechanisms for coupling, may be important in understanding the remnant state of these minerals on Mars.

Application of ion beam analysis techniques for the investigation of the oxidation and corrosion resistance of low-energy high-flux nitrogen-implanted stainless steel

Rutherford Backscattering spectrometry (RBS), nuclear reaction analysis (NRA) and scanning electron microscopy (SEM) were applied to characterize and study the thermal oxidation (in air at 500 °C) and corrosion (in 0.5 M HCl at 50 °C) resistance of AISI 304L stainless steel samples implanted with high flux (1 mA/cm 2) low energy (1.2 keV) nitrogen ions (dose ca. 3.5 × 10 19 ions/cm 2) at 400 and 500 °C. The implantation led to the formation of a high nitrogen content (ca. 30 wt.%) metastable fcc interstitial nitrogen solid solution also exhibiting increased hardness and wear resistance. The results of this study showed that the steel samples implanted at 400 °C exhibited increased hardness and considerably improved corrosion resistance but reduced oxidation resistance at 500 °C. On the other hand, the nitrogen implantation at 500 °C led to a drastically increased surface hardness of the steel but also to a considerable reduction of its corrosion resistance. The oxidation resistance of these samples was found to be only slightly affected.

Effects of Al doping on SnO 2 nanofibers in hydrogen sensor

Pristine SnO 2 and Al-doped SnO 2 composite nanofibers, with several dopants concentrations, have been fabricated via electrospinning technique and subsequent calcination procedure. The morphology, structure, and composition of the as-prepared nanofibers are characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), and energy dispersive X-ray spectrometer (EDX), respectively. XRD analysis indicates Al–SnO 2 metastable solid solution is formed at the low concentrations, while the Al 2O 3–SnO 2 heterojunction structures can be obtained at high concentrations. Comparing with the pristine SnO 2 nanofibers, Al-doped SnO 2 composite nanofibers show improved hydrogen sensing properties, with the Al–SnO 2 metastable solid solution having the best performances, such as higher sensitivity and rapid response (∼3 s) and recovery (less than 2 s). Effects of the changes of SnO 2 crystal, causing by the induction of Al, on the sensing performance have been discussed. We believe this paper can construct a powerful platform to understand and design the practical gas sensor in future.

Investigation of thermal properties of double complex salts [M(NH3)5Br][AuBr4]2·nH2O, M = Rh, Ir

Novel double complex salts [M(NH3)5Br][AuBr4]2·nH2O, M = Rh, Ir, have been synthesized and examined. The processes of thermal decomposition of the compounds in inert and reductive atmospheres have been studied and intermediate products identified. Simultaneous thermal analysis with parallel mass-spectrometric analysis of evolved gases (STA-EGA) has been employed for identification of main gaseous products of thermolysis in inert atmosphere. It has been revealed that the final products of decomposition in inert or reductive atmospheres are fine powders of gold and the corresponding platinum metal with sizes of crystallites 4–40 nm. The possibility of preparation of the metastable solid solution Au0.05Ir0.95 on thermolysis of [Ir(NH3)5Br][AuBr4]2·H2O in inert atmosphere has been demonstrated.

Magnetron sputtered nanocrystalline metastable (V,Al)(C,N) hard coatings

Nanocrystalline hard coatings of the system V–Al–C–N with an f.c.c. metastable solid solution (V,Al)(N,C) microstructure were deposited by non-reactive r.f.-magnetron sputtering of a ceramic compound target (composition: 60mol.% VC and 40mol.% AIN) in a pure argon discharge at 1.1Pa. The chemical composition of the as-deposited coatings was determined by electron probe micro analysis (EPMA). The microstructure of the thin films was characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM), and selected area electron diffraction (SAED). The influence of a moderate argon ion bombardment during thin film deposition, realized through the variation of the argon ion energy in the range 20eV–170eV, as a means to adjust the adatom surface mobility and surface diffusion processes, on the microstructure evolution and on the Vickers micro-hardness is discussed. The conditions for the formation of a metastable solid solution f.c.c. (V,AI)(C,N) thin film microstructure are described in terms of surface processes during film growth and thermodynamic considerations. It was demonstrated, that a metastable phase formation in the quaternary material system V–Al–C–N can easily be adjusted in magnetron sputter deposition.

Chemical and magnetic properties of rapidly cooled metastable ferri-ilmenite solid solutions: implications for magnetic self-reversal and exchange bias-I. Fe-Ti order transition in quenched synthetic ilmenite 61

SUMMARY Quenched ferri-ilmenite solid solutions X FeTiO3 + (1 – X )F e2O3 with X ≈ 0.60 contain chemical and magnetic structures important for understanding the unusual magnetic properties in this series, including self-reversal in igneous rocks and exchange bias. Here we study a composition X = 0.61, annealed at 1055 ◦ C, above the Fe-Ti ordering temperature, then quenched. Presence of two interface-coupled phases is established by pot-bellied character of theroom-temperature magnetic hysteresisloop,andlargenegative magnetic exchange biasbelow 30K. Transmission electron microscopy (TEM) dark-field imaging with the 003 reflection shows dominant Fe-Ti disordered antiferromagnetic and lesser ordered ferrimagnetic phases, the latter in lenses ≤8 nm thick. Parts of the ordered phase are in antiphase relationship, shown by high-resolution TEM imaging of Fe-rich and Ti-rich layers. TEM-EDX analyses indicate chemical phase separation during quench, with dominant compositions X = 0.56–0.63, extremes 0.50 and 0.70. Thermomagnetic experiments indicate compositions X = 0.56–0.61 are antiferromagnetic, X = 0.61–0.64 are ferrimagnetic. A sample held ∼5 min at 1063K, increased in order, demonstrated by twofold increase in induced moment at 1T. This then acquired self-reversed thermoremanent magnetization between 490 and 440K. Progressive annealings of another sample at 773K, 973K, 1023K and 1063K, followed by cooling in a 1T field, produced positive room-temperature magnetic exchange bias, only for 1023K and 1063K runs. These properties suggest growth of ordered regions from disordered regions, and expansion of some ordered domains against others across antiphase boundaries, thus creating self-organized structures essential for magnetic self-reversal and magnetic exchange bias.

Near Heterosite Li0.1FePO4 Phase Formation as Atmospheric Aging Product of LiFePO4/C Composite. Electrochemical, Magnetic and EPR Study

Freeze-drying method was employed in order to synthesize a LiFePO4/C composite. This method produced phosphate nanoparticles (10–20 nm size) covered in a carbon network. Nanostructuring and homogeneous conductive web around the active material promoted a good electrochemical response, with 141 mAh · g−1 at C/1 and a capacity retention of 90% up to 300 cycles. However, XRD measurements showed the presence of an approximately 30% of a near heterosite Li0.1FePO4 intermediate phase in the initial sample, as a product of atmospheric aging. EPR spectrum displayed a very broad signal attributed to a high spin Fe3+ ion magnetically coupled to Fe2+, confirming the formation of the non stoichiometric LixFePO4 compound. Electrochemical measurements indicated the presence of active Fe3+ in the initial composite, in a structural environment close to that of a FePO4 heterosite system. A post-mortem cathode, stopped at 4 V, was characterized. Metastable LixFePO4 solid solution type phase was not noticed. Thus, it would have disappeared during cathode cycling life, and all active material would have evolved to a classic biphasic system.

The electrochemical properties of melt-spun Al–Si–Cu alloys

Melt spinning was used to prepare Al 75− X Si 25Cu X ( X = 1, 4, 7, 10 mol%) alloy anode materials for lithium-ion batteries. A metastable supersaturated solid solution of Si and Cu in fcc-Al, α-Si and Al 2Cu co-existed in the alloys. Nano-scaled α-Al grains, as the matrix, formed in the as-quenched ribbons. The Al 74Si 25Cu 1 and Al 71Si 25Cu 4 anodes exhibited initial discharge specific capacities of 1539 mAh g −1, 1324 mAh g −1 and reversible capacities above 472 mAh g −1, 508 mAh g −1 at the 20th cycle, respectively. The specific capacities reduced as the increase of the Cu content. AlLi intermetallic compound was detected in the lithiated alloys. It is concluded that the lithiation mechanism of the Al–Si-based alloys can be affected by the third component. The structural evolution and volume variation can be mitigated due to the formation of non-equilibrium state and the co-existence of nano-scaled α-Al, α-Si, and Al 2Cu for the present alloys.

Combinatorial approach to the growth of α-(Al1 − x,Crx)2 + δ(O1 − y,Ny)3 solid solution strengthened thin films by reactive r.f. magnetron sputtering

The design and synthesis of Al–Cr–O–N thin films in a metastable solid solution strengthened α-(Al1−x,Crx)2+δ(O1−y,Ny)3 microstructure are described. The deposition experiments were carried out by reactive r.f. magnetron sputtering in an argon–oxygen–nitrogen atmosphere for the sputtering from a segmented target, composed of an Al half plate and a Cr half plate. The constitution, microstructure and Vickers micro hardness of the coatings are discussed in dependence of the deposition parameters and the elemental composition. The range of α-(Al1−x,Crx)2+δ(O1−y,Ny)3 phase formation is shifted to higher Cr/(Al+Cr) ratios with increasing nitrogen gas flow. A γ-Al–Cr–O–N phase is formed at high total gas pressures and low Cr/(Al+Cr) ratios. The solid solution strengthening in the quaternary material system leads to a significant Vickers micro hardness increase compared to α-(Al1−x,Crx)2O3 coatings deposited in the same PVD machine under corresponding process parameters. The α-(Al1−x,Crx)2+δ(O1−y,Ny)3 thin films offer an additional restraint of the lattice by the incorporation of nitrogen and therefore higher Vickers micro hardness values are measured compared to the Al–Cr–O material system.

Formation of Nanostructures in Ni-22Cr-11Fe-1&lt;I&gt;X&lt;/I&gt; (&lt;I&gt;X&lt;/I&gt; = Y&lt;SUB&gt;2&lt;/SUB&gt;O&lt;SUB&gt;3&lt;/SUB&gt;, TiO&lt;SUB&gt;2&lt;/SUB&gt;) Alloys by High-Energy Ball-Milling

Powder mixtures of Ni, Cr, Fe and Y2O3 were high-energy ball-milled and subsequently sintered to fabricate Ni-based oxide-dispersion strengthened (ODS) alloys. Nano-sized Y2O3 and/or TiO2 seem to be dissolved in the Ni matrix forming a metastable solid solution during high-energy ball-milling or mechanical alloying (MA) process. The finely grained MA powders with high dislocation density facilitated the decomposition of oxides. The MA powders were consolidated to near-full density by spark plasma sintering at 1100 degrees C for 5 minutes in an Ar atmosphere. The Cr oxides as well as decomposed Y- and Ti-oxides thermally precipitated as oxide particles of several tens nanometers at this temperature, although sintering was carried out during a short time. The SPSed specimen showed a near full densification with almost pore-free microstructures. Examination of fractured surface showed a typical dimple rupture with fine and homogeneous distribution of dispersoids, indicating non-negligible room temperature ductility combined with high mechanical strength.

Stable Ti/IrO&lt;sub&gt;2 &lt;/sub&gt;Anode with Iridium-Titanium Oxide Interlayers for O&lt;sub&gt;2&lt;/sub&gt; Evolution

Ti/IrOx–TiO2/IrO2 and Ti/IrO2–Ta2O5 electrodes were prepared using thermal decomposition procedure, respectively. The microstructure and electrochemical properties of the electrodes were studied with scanning electron microscope (SEM), X-ray diffraction (XRD), potentiodynamic polarization and accelerated life test. Experimental results showed that the Ti/IrOx–TiO2/IrO2 electrode has better electrocatalytic activity for oxygen evolution and higher stability, compared with the Ti/IrO2–Ta2O5 electrode under the same conditions. The high electrocatalytic activity of Ti/IrOx–TiO2/IrO2 electrode could be correlated with a large number of IrO2 particles on coating surface. The Ti/IrOx–TiO2/IrO2 electrode exhibits a three times longer service life than that of Ti/IrO2–Ta2O5, its superior stability was attributed to the IrOx–TiO2 interlayer, which contributes to form a metastable solid solution between IrOx and thin titanium oxide layer on titanium substrate during calcination and the improvement of the bonding of IrO2 layer with the substrate.

Electrodeposition of Pt100−xPbx Metastable Alloys and Intermetallics

The electrodeposition of a series of metastable Pt-Pb alloys and intermetallic phases as well as elemental Pt is demonstrated using an acid electrolyte comprised of 0.05 mol/l Pb(ClO4)2 and/or 0.001 mol/l K2PtCl4. Pt-Pb films were deposited at various potentials relative to the reversible potential for Pb/Pb2+ (EPb/Pb2+ = −0.80 V SSE). A metastable fcc Pt-Pb solid solution is formed at potentials between −0.2 and −0.78 V SSE. A monotonic increase in the fcc lattice parameter with decreasing potential corresponds to a rise in Pb content that spans the composition range from Pt to beyond Pt3Pb. The intermetallics, PtPb, PtPb4 and elemental Pb form at more negative potentials. The films are single or multiphase depending on the growth potential and substrate. Thermal annealing leads to phase separation of the deposits into the respective equilibrium intermetallic phases whose volume fractions enable the overall film composition to be determined. At more negative potentials, between −0.79 and −0.82 V SSE, the ordered hexagonal PtPb intermetallic phase is directly formed by electrodeposition. Co-deposition of Pt100−xPbx at potentials positive of −0.8 V SSE (EPb/Pb2+) occurs by a combination of Pb underpotential deposition with overpotential Pt deposition.

Annealing behaviour of sub-stoichiometric Ti(C,N)–W mechanical alloy powders

The annealing behaviour of Ti(C 0.5N 0.05)–40 wt.% W and Ti(C 0.5N 0.5) 0.6–40 wt.% W mechanically alloyed powders was investigated using XRD, TEM, SEM and DTA techniques. It was observed that the reaction start and finish temperatures between constituents were lower in the system that had higher residual lattice strains after milling. The compositions of the intermetallic compounds and solution phases formed were dependent of the milling conditions and the annealing temperature. Thermal alloying was observed during annealing of Ti(C 0.5N 0.05)–40 wt.% W mechanically alloyed products, whereas de-mixing of W-rich phases from the metastable solid solution occurred during annealing of the Ti(C 0.5N 0.5) 0.6–40 wt.% W milled powders.

Metastable phase formation during flame spray pyrolysis of ZrO 2(Y 2O 3)–Al 2O 3 nanoparticles

Nanoparticles with the composition (1 − x mol.%) [ZrO 2 (3 mol.% Y 2 O 3 )]–( x mol.%) Al 2 O 3 , with x ranging from 0 to 1, were prepared by liquid-feed flame spray pyrolysis. The effect of the alumina content on the morphology and phase formation was studied by means of X-ray diffraction, nitrogen adsorption and transmission electron microscopy. It is shown that alumina can be incorporated into the nanoparticles at levels above the solubility limit, leading to the formation of metastable extended solid solutions and core–shell nanoparticles.

Lithium–thallium(i) butyrates binary system: an intermediate salt and liquid crystal from non-mesogenic compounds.

The binary system between lithium and thallium(I) butyrates, [xLiC3H7CO2 + (1 − x) TlC3H7CO2], where x = mole fraction, has been carefully analyzed, solving the temperature and enthalpy vs. composition phase diagrams. The formation of an intermediate salt or complex with a composition (2 : 1), an ionic liquid crystal phase and a metastable solid solution has been detected. The complex melts incongruently at Tfus = 494.7 K, with ΔfusHm = 7.70 kJ per mol of mixture. Its low temperature crystal structure (monoclinic, P21/c) has been solved and refined using X-ray synchrotron radiation and has been found to be bilayered, as is typical from pure metal alkanoates and, as it happens, for other two analogous intermediate salts studied recently by our group. The liquid crystal phase detected is formed from two non-mesogenic pure compounds, appearing in the binary system between 394.1 and 436.6 K and for x = 0.10 up to x = 0.29. Binary phase diagrams are shown to be a powerful tool to detect and predict the formation of liquid crystal phases and mixed crystals.

Transmission electron microscopy and first-principles calculations of hydrogen ordering inβ-YH2+x

In ${\text{YH}}_{2+x}$ hydrides stoichiometric deviations are associated with various interesting phenomena such as magnetic transitions and metal-insulator transitions; ordering of hydrogen on the octahedral sites (O sites) was suggested to be responsible. Long-range order was discovered in hydrogenated Y films by electron diffraction and high-resolution transmission electron microscopy. Ordering on interstitial O sites in the fcc-based ${\text{Y}}_{\text{fcc}}{\text{H}}_{2+x}$ solid solution $(0&lt;x&lt;1)$ was investigated with computational tools from the Alloy Theoretic Automated Toolkit. The resulting set of 94 structure energies was fit to a cluster-expansion Hamiltonian that was used to perform a ground-state analysis for the mostly metastable fcc-based solid solution and for the more stable ${\text{Y}}_{\text{fcc}}{\text{H}}_{2+x}+{\text{Y}}_{\text{hcp}}{\text{H}}_{2+x}$ two-phase mixture. The calculated structures were tested by the observed diffraction conditions and two possible ordered structures were suggested, a ground-state triclinic $x=0.0625$ and an I-centered cubic $x=0.375$.

Cu-Rich Scales in the Reykjanes Geothermal System, Iceland

Seawater-dominated fluids discharge from the subaerial Reykjanes geothermal system, Iceland. There is a sharp pressure decrease in surface pipes at an orifice (throttle point), and Cu-rich scales deposit at this orifice that consist largely of bornite and digenite, along with sphalerite and other sulfides. The bornite and digenite form complex intergrowths with sphalerite and galena, accompanied by high concentrations of gold and silver (up to 590 ppm and 2.3 wt %, respectively). The precipitates form in response to rapid boiling (flashing) of the hydrothermal fluids due to the sharp decrease in pressure (~37–22 bars) at the orifice, downstream of the well-head. The boiling, and concomitant separation of the vapor phase, results in a temperature decrease from 252° to 220°C across this throttle over distances of centimeters. There is a nearly quantitative deposition of metals from solution compared to concentrations in reservoir liquids, resulting in formation of the metastable Cu-FeS solid solution, rich in silver and gold, plus sphalerite and galena. A high degree of supersaturation of metals in the quenched liquid is indicated by the very fine grain size of the sulfides and dendritic textures. Postdepositional cooling likely caused exsolution of bornite and digenite from the high-temperature solid solution; in addition, silver was expelled from the Cu-Fe-S solid solution and remobilized into late fractures in the scales, whereas the gold appears to have remained in solid solution or as submicroscopic inclusions in the bornite and digenite. The observed mineral assemblage at Reykjanes contrasts with that of sea-floor black smokers, despite similar fluid compositions. The sea-floor hydrothermal vents characteristically have Cu-rich linings composed predominantly of chalcopyrite, which is precipitated by a combination of conductive cooling of high-temperature (~350°C) hydrothermal fluids and mixing with seawater. The difference in sulfide mineralogy between the Reykjanes orifice scales, with Cu sulfides dominated by bornite and digenite, and many sea-floor vents may provide an indication of the subsea-floor mineralization where fluids boil before discharging at sea-floor vents.

Preparation, microstructure and properties of Al-Zn-Mg-Sc alloy tubes

The Al-6.0Zn-2.0Mg-0.2Sc-0.10Zr hollow tube ingots, prepared by semi-continuous casting technology, were subjected to homogenization treatment, hot extrusion, intermediate annealing, tension, solution and aging treatment. The microstructures and properties of as-cast Al-Zn-Mg-Sc alloy at different homogenization treatment conditions were studied using hardness measurement, X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) analysis. The results showed that the phases in the as-cast Al-Zn-Mg-Sc alloy were α(Al) and T(Mg 32(Al,Zn) 49). The metastable supersaturation solid solution decomposed firstly. Then the equilibrium T phases and dispersed Al 3(Sc,Zr) particles precipitated and dissolved into the solution matrixes at high homogenization temperature. The appropriate homogenization processing was determined to be 470 °C for 24 h. The microstructures after extrusion were non-recrystallized grains because of dispersed Al 3(Sc,Zr) particles. After intermediate annealing most of the deformed microstructures were eliminated and softened. During solution treatment the equilibrium phases dissolved into the matrix, leading to the formation of supersaturation solid solution. The η' phases precipitated from the solid solution during aging process. The η' phases in the grain and the equilibrium phases on the grain boundaries were coarsening and the precipitate free zone (PFZ) was wider with increasing of the aging temperature and time. The suitable heat treatment for Al-Zn-Mg-Sc-Zr aluminum tubes was solution treated at 470 °C for 1 h, followed by aging at 120 °C for 24 h. At this condition, the ultimate tensile strength, yield strength and elongation could reach 520 MPa, 510 MPa and 11%, respectively. The high strength was mainly due to the fine grain strengthening caused by the addition of Sc and Zr, the subgrain strengthening and precipitation strengthening of Al 3(Sc,Zr) particles and η' phase.