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The application of 6005A aluminum alloy in transportation is increasing, which puts forward higher requirements for the fatigue performance of welding process. In this study, friction stir welding (FSW) enhanced treatment was applied on the traditional metal inert gas (MIG) weld. The results show that the fatigue life of FSW plate is three times higher than that of original MIG welded plate at 140 MPa stress level. Under 107 cycles, the fatigue life limit was increased by 16 MPa compared with as-received MIG plate. The main reason of FSW leading to the increasing fatigue life are the reduction of porosity to reduce crack initiation and grain refinement to delay crack propagation.

The effect of cold rolling and annealing on the microstructure and properties of an Fe–13Cr–4.5Al–2.2Mo–1.1Nb alloy was investigated. The results showed that the recrystallization rate increased with increasing annealing temperature and rolling reduction. Recrystallization kinetics was constructed based on Johnson–Mehl–Avrami–Kolmogorov equation. The apparent activation energies of recrystallization were 161.385, 144.770, and 95.362 kJ/mol for the samples with 30%, 50%, and 70% cold-rolling reduction, respectively. With the cold-rolling reduction increasing, the texture γ fiber partly changed to 〈100〉//ND. After annealing, γ fiber of the alloy with 30% thickness reduction retained, the subgrains disappeared through merging, and the proportion of coincident site lattice grain boundaries increased and became more continuous. 30% cold-rolling reduction alloy annealed at 730 °C for 120 min not only possessed relatively high yield strength (YS) of ~ 730 MPa and ultimate tensile strength (UTS) of ~ 880 MPa, but also exhibited elongation of ~ 16% at room temperature. After annealing at 730 °C for 120 min, 70% cold-rolled alloy has finer and more uniform grain, with higher elongation of ~ 22%, YS of ~ 615 MPa and UTS of ~ 774 MPa. The mechanism of mechanical properties difference was explained according to Schmid factor analysis. These results provided an effective way for tuning strength and ductility of FeCrAl alloy.

In this paper, the Widmanstatten microstructure in an extruded near-α titanium alloy (Ti-5.5Al-2Zr-1Mo-2.5V) pipe was changed effectively by solid solution treatment at 920 °C for 2 h. The treatment produced intermittent lamellar α and discontinuous α grain boundaries (αGB), and aging at 450 °C for 2 h introduced a high density of nanosized secondary α (αs). The microstructure consisted of the lamellar α, αGB and transformed β demonstrated a good combination of yield strength 1064 MPa and elongation 10.5%. Severe plastic deformation occurred inside the lamellar α during the tensile process, resulting in high-density dislocation tangles and dislocation cells. Furthermore, the stretching imposed on the tensile sample before aging generated dislocations, which piled up near the α/β interface. Thus, a coordinated deformation between lamellar α and transformed β, and the resultant strain partition contributed to an improvement in the ductility. Moreover, dislocation motion was effectively obstructed near the α/β interfaces, which dramatically strengthened the alloy. A solid solution at a middle temperature in the α + β region and aging at a low temperature provided an effective way to improve the strength and ductility simultaneously in titanium alloys with Widmanstatten microstructure.

Composites of graphene nanoplatelets (GNPs) and 8030 aluminum alloy powder were prepared using powder modification + semisolid extrusion processes. The density, electrical conductivity, mechanical properties and microstructure of the specimens were investigated. The results show that the composites with 0.5 wt% GNPs achieved an enhancement in yield strength (37.5%) and ultimate tensile strength (62.9%), while its elongation and electrical conductivity were comparable, as compared with the 8030 aluminum alloy without GNPs prepared by the same process. Furthermore, the related strengthening mechanism of the composites with GNPs directional distribution was discussed.

Grains with size of 4.5–20.5 μm were studied for their corrosion behavior and electrochemical performance in a Mg-3Al-5Pb-1Ga-Y sacrificial anode using immersion testing, electrochemical measurements and microstructure analysis. The results show that fine-grained microstructure has higher chemical activity and more negative discharge potentials than coarse-grained samples. The sample with the smallest average grain size of 4.5 μm exhibits corrosion current density of 7.473 × 10−5 A/cm2, and work potentials of −1.721 V at current density of 10 mA/cm2. The density of grain boundaries and LAGBs increases with grain refinement, which leads to higher rates of dissolution and diffusion for the atoms. The secondary phases promote the occurrence of corrosion and improve the chemical activity of alloy due to their higher potential than the substrate. Higher corrosion rate and discharge activity are directly attributed to the higher density of grain boundaries and LAGBs, as well as the secondary phase.

The plastic deformation processes and fracture behavior of a Ti–5Al–5Mo–5V–1Cr–1Fe alloy with bimodal and lamellar microstructures were studied by room-temperature tensile tests with in situ scanning electron microscopy (SEM) observations. The results indicate that a bimodal microstructure has a lower strength but higher ductility than a lamellar microstructure. For the bimodal microstructure, parallel, deep slip bands (SBs) are first noticed in the primary α (αp) phase lying at an angle of about 45° to the direction of the applied tension, while they are first observed in the coarse lath α (αL) phase or its interface at grain boundaries (GBs) for the lamellar microstructure. The β matrix undergoes larger plastic deformation than the αL phase in the bimodal microstructure before fracture. Microcracks are prone to nucleate at the αp/β interface and interconnect, finally causing the fracture of the bimodal microstructure. The plastic deformation is mainly restricted to within the coarse αL phase at GBs, which promotes the formation of microcracks and the intergranular fracture of the lamellar microstructure.

The corrosion behaviors of CP Ti, Ti-Ru, Ti-6Al-4V-Ru (Ti-64-Ru) and Ti-5Al-5Mo-5V-1Cr-1Fe-Ru (Ti-55511-Ru) in HCl solution were investigated using open circuit potential, polarization curves, mass...

We herein report our investigation into the influence of cold-rolling on the recrystallization texture of the Zr-1Sn-0.3Nb-0.3Fe-0.1Cr alloy during annealing. The as-received plates were cold-rolled at 25 °C with different reductions of 6, 10, 14, 18, 30, 40, 50 and 70%. All cold-rolled sheets were annealed at 580 °C for 3 h, while 14 and 30% cold-rolled samples were also annealed at 580 °C for 12 h. The microstructures of the annealed samples were characterized by scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD). Abnormal grains growth with about 23 μm in size appeared in the samples with 14% reduction and annealed at 580 °C for 3 h, which corresponded to the critical degree of alloy deformation. The texture of the 14% cold-rolled sheet was typical rolling texture //ND, after annealing, cold rolling texture was still retained. While the texture of the 30% cold-rolled sheet was 2 ¯ 0> parallel to the rolling direction ( 2 ¯ 0>//RD), which changed to the recrystallization texture //ND, 1 ¯ 0>//RD and 2 ¯ 0>//RD characteristics after annealing. The loading direction is along the rolling direction (RD), the slip system and the Schmid factor are analyzed to more deeply understand and evaluate the plasticity of further rolling or punching. When the loading direction is along the rolling direction (RD), the predominant slip systems of annealed 14% reduction samples was prismatic and pyramidal plane system, and the annealed 30% reduction samples were prismatic with a pyramidal plane system. This implies that the use of 30% cold-rolled reduction and annealing at 580 °C for 12 h imparts a superior plasticity to the alloy, which may allow its application in future deformations, such as rolling or punching.

The objective of the present study is to investigate the high-cycle fatigue (HCF) and fatigue crack propagation (FCP) characteristic in relation to the microstructure in the 5083-O aluminum alloy. The HCF strengths of the 5083-O Al alloy in parallel to rolling direction (PD) and vertical to rolling direction (VD) specimens are 164 MPa and 165 MPa, respectively, However, the FCP resistance of the specimens reveals evident anisotropy. The FCP resistance of the PD specimen is less than that of the VD specimen, which is predominantly caused by the main crack expanding along the chain-shaped coarse inclusions in PD specimen. These chain-shaped coarse inclusions, particularly, Fe/Mn containing particles with secondary microcracks, might accelerate FCP rate and decrease FCP resistance.

Microstructure characteristics and restoration mechanism were studied in a near-β Ti-5Al-5Mo-5V-1Cr-1Fe alloy after the single- and multi-pass compression at 800 °C (below the β-transus) and 950 °C (above the β-transus) with the strain rate of 5s−1, 30s−1 and 50s−1. The results showed that the restoration mechanism of the alloy in β phase during the compression in β phase region was dynamic recovery (DRV) while DRV and dynamic recrystallization (DRX) occurred during the compression in α+β region. The involvement of α phase in α+β phase region promoted the DRX of β phase. Multi-pass compression at 800 °C has greater impact on the microstructure evolution of the alloy than strain rate change. The frequency of fine β grains/subgrains (grain size of 0∼5 μm) in the 800 °C/5-pass compressed sample was significantly higher than that in the 800 °C/1-pass compressed one. 5-pass compression at 800 °C results in enhanced fragmented α, which promoted the formation of finer β subgrains by introducing the heterogeneous deformation. This deformation route provides an effective way to obtain fine subgrain structure for quick forging parts of this alloy.

A spheroidal Al3(Zr,Sc) precipitate with a double-shell structure, comprising a Sc-enriched core enveloped by a Zr-enriched inner shell and a Sc-enriched outer shell (∼9 nm in thickness), appears in an Al–0.2Zr–0.1Sc alloy cable after thermomechanical treatment. The average diameter of the spheroidal Al3(Zr,Sc) precipitate is approximately 80 nm. The double-shelled Al3(Zr,Sc) precipitate presents three different interfaces and is semi-coherent with the Al matrix. Atom probe tomography (APT) analyses further show that the outer shell of Al3(Zr,Sc) precipitate is Sc element enrichment. The electrical conductivity of Al–0.2Zr–0.1Sc alloy cable increases by 6.5 MS/m within the aging time from 0.2 to 100 h at 350 °C, with double-shelled Al3(Zr,Sc) precipitate.

In this study, 0.2 wt% zirconium (Zr) added Sn–1.0Ag–0.5Cu (SAC105) lead-free solder alloy was prepared and its microstructure, tensile property, and aging stability were investigated and compared with the original SAC105 solder alloy. The SAC105 and SAC105-0.2Zr solder alloys were fabricated by vacuum induction melting method. The results showed that the Zr-added SAC105 solder exhibited a significantly refined microstructure. The primary β-Sn phases, Ag3Sn particle size, and spacing of Ag3Sn had been obviously reduced with the addition of trace amounts of Zr. The tensile test demonstrated that both strength and elongation of the SAC105-0.2Zr solder improved because of the finer microstructure. Isothermal aging was performed at 180 °C for 36 h, 84 h, and 156 h. The existence of Zr could significantly inhibit the coarsening of the Ag3Sn phases, thus enhancing the microstructure stability under severe aging conditions. Moreover, the Zr-added SAC105 solder showed significant decrease in supercooling, but the melting range was almost unchanged.

Alumina-reinforced copper matrix composites with Ag addition were fabricated by internal oxidation. The effects of slight Ag addition (0.92 at%) on electrical conductivity (EC) and oxidation resistance of internal-oxidized copper alumina composites were investigated. The annealing treatments were carried out to promote the diffusion of Ag in copper matrix. Ag was observed to segregate at Cu/Al2O3 interface after being annealed, which may lead to the lower interfacial energy between Al2O3 and copper matrix. The EC increased more than 7.8% after Ag was added. Moreover, annealing Cu Al2O3 Ag composite at 500 °C for 10 h results in the improvements of both oxidation resistance and EC. The initial oxidation temperature increased from 169 °C to 189 °C and the EC increased from 81.98 ± 0.56% International Annealed Copper Standard (IACS) to 88.19 ± 0.27%IACS. While the EC of Cu Al2O3 composites always remained ∼76%IACS which suggests that the annealing treatment has insignificant impacts on EC of Cu Al2O3 without Ag.

Four component solder alloys (Sn-3.0Ag-0.5Cu-xZr; x = 0, 0.05, 0.2, and 0.5 wt%) were obtained using vacuum induction melting. The microstructure of the solder alloys and solder joints was characterized via OM, SEM, XRD and EPMA. Tensile and shear tests were performed to evaluate the mechanical properties. The results showed that with the increase of the Zr content, the size of the primary β-Sn phases decreased gradually, and Ag3Sn decreased first and then increased. The SAC305-0.2Zr solder exhibited the finest microstructure. The size of the primary β-Sn phase decreased by 59%, and the Ag3Sn resembled a dot 1 μm in size. Tensile tests indicated that as the Zr content increased, the strength of the solder increased, and the elongation first increased and then decreased. Compared to the original joints, the joints fabricated with Zr-modified solders had thinner intermetallic compound (IMC) layers and exhibited higher shear strength. The SAC305-0.2Zr/Cu joints had a 17% reduction in the interfacial reaction layer thickness and a 20% increase in the maximum shear force. Moreover, the Zr-modified solders showed a significant decline in undercooling. The melting range and melting point was slightly reduced. In this study, 0.2 wt% was determined to be the optimum amount of Zr in the SAC305 solder.

Theoretical models for predicting the change of electrical resistivity of Al–Zr–Sc cable with Al3(Zr,Sc) core–shell dispersoids during aging were developed through integrating thin slices of core–shell cell. The theoretical electrical resistivity decreased with increasing volume fraction and size of dispersoids. As the aging time at 350 °C increased from 0.2 to 400 h, the experimental electrical resistivity of aged Al–Zr specimens decreased from 3.46 to 2.77 μW cm, and that of Al–Zr–Sc specimen decreased from 3.65 to 2.93 μΩ cm. Meanwhile, the theoretical electrical resistivity of aged Al–Zr–Sc specimen ranged from 3.6 to 2.85 μΩ cm, showing the prediction matched well the experimental results. The difference in the electrical resistivity between Al–Zr and Al–Zr–Sc specimens may be caused by the shell of the Al3(Zr,Sc) dispersoids. The possible scope of electrical resistivity difference value ranged from 0.05 to 0.20 μΩ cm.

α Macrozones are usually observed in near-α/α+β titanium alloys but have not been reported in near-β titanium alloys. This article shows that a new type of α macrozone has been observed using electron backscatter diffraction (EBSD)-orientation maps in a near-β titanium alloy Ti-5Al-5Mo-5V-1Cr-1Fe after thermo-mechanical processing. The microstructure in the macrozone was comprised of primary α plates (αp) and secondary α platelets (αs) with insignificant differences in shape. The majority of α platelets had similar orientation after aging.

The surface stability and equilibrium morphology of MoO3 were investigated by the first principles calculations. The thermodynamic energies of the stoichiometric surfaces of MoO3 are in the order (0 1 0)

Microstructure plays a crucial role on mechanical properties of materials. The as-prepared Al-Cu-Li alloy exhibits excellent thermal stability during longer aging treatment at 160 °C. Transmission electron microscopy, high angle annular dark field scanning transmission electron microscopy and first-principle energy calculations were used to evaluate the evolution of different phases in the alloy. The results show that the microstructure evolution goes as follows: SSS→δ′, θ′, T1→θ′, T1, cubic Al5Cu6Li2 phase. The cubic Al5Cu6Li2 phase was not precipitated from the matrix until 104 h aging, and the number density increased with prolonging of aging time. Its formation compensates the strength loss caused by the decreased number density and coarsening of θ′(Al2Cu) and T1(Al2CuLi) during longer aging treatment.

Ni-based self-lubricating composites containing a fixed amount of hexagonal boron nitride (h-BN) (5 wt%) and different amounts of graphene (0–1.5 wt%) were prepared by ultrasonic dispersion, high-energy ball milling, and spark plasma sintering. The effects of the graphene content on the physical, mechanical, and wear properties of the Ni/h-BN composites were evaluated. These properties were first enhanced with increasing graphene content, reaching optimal behavior for a graphene content of 1 wt%, and then degraded with further graphene addition. Compared to the pure Ni/h-BN composite, the relative density, hardness, and bending strength of the composite with 1 wt% graphene increased by 2.7%, 7.4%, and 6.3%, respectively, while the friction coefficient decreased by 56% to 0.31, and a reduction in wear rate by a factor of 5–15 was observed. The mechanism for improving the wear properties of the composite with added graphene was due to the formation of a graphene lubricating film on the worn surface, which increased the load bearing capacity of the surface and enhanced lubrication during wear.

The precipitation behavior of a cast Al-4.5Cu-3.5Zn-0.5Mg alloy was comprehensively analyzed using differential scanning calorimetry (DSC), Vickers hardness measurement, electrical conductivity measurement, and transmission electron microscopy (TEM). The results revealed that three exothermic reactions occur during the heating process of DSC, giving rise to exothermic peaks at around 130, 250, and 280 °C due to the formation of Guinier-Preston (GP) zones and the precipitation of Ω phase and θ′ phase, respectively. TEM observations indicated that the predominant phase was the Ω phase, with only small amounts of the θ′ phase precipitating at 280 °C. STEM analysis showed that elements Zn and Mg segregate at the Ω–α interface. The precipitation of the Ω phase was remarkably promoted by the addition of Zn. The tensile strength and elongation heated up to 280 °C with the heating rate of 5 °C/min were 403 MPa and 9.2%, respectively. It was thus concluded that the precipitation sequence of the cast alloy was supersaturated solid solution (SSS)→GP zone→Ω phase→θ′ phase. The cast alloy possesses high strength and high toughness due to the predominance of the Ω phase and the lack of substantial θ′ phase.

The effect of the addition of 0.1 wt% Sc and 0.1 wt% Er on the deformation microstructure, Vickers microhardness, and electrical conductivity of Al-0.2 wt% Zr-based alloy cables annealed at 400 °C for different times was investigated. The comprehensive properties of Al-0.2Zr-0.1Sc were better than those of Al-0.2Zr-0.1Er. The optimal conditions for the Al-0.2Zr-01Sc alloy cable were a microhardness of 575 MPa, an electrical conductivity of 34.5 MS/m for an annealing time of 36 h, and those for the Al-0.2Zr-0.1Er alloy cable were a microhardness of 550 MPa, an electrical conductivity of 33.6 MS/m for an annealing time of 8 h. During the annealing process, dispersed Al3(Zr,Sc/Er) precipitates were generated, which substantially impeded recrystallization by Zener pining of grain boundaries. Based on the ratio of volume fraction (FV) to average diameter ( d ¯ ) of the precipitates, their capability to inhibit recrystallization was as follows: Al3(Zr, Sc) > Al3(Zr, Er) > Al3Zr. Moreover, the electrical conductivity of Al-0.2Zr-0.1Sc was better than that of Al-0.2Zr-0.1Er, probably because Sc could better inhibit recrystallization than Er, leading to fewer grain boundaries and hence lesser electron scattering.

In this study, the effect of Sc content on the phase transformation of the 2519 alloy during solidification is investigated through microstructure characterization and thermodynamic calculations. The results show that the grain size of the 0.3–0.4Sc alloy is reduced by 70% (approximately 28.9 μm) to achieve maximum refinement in the as-cast 2519(Sc) Al alloy. The phase diagram calculation shows that the sequence of intermetallic formation during the solidification of 2519(Sc) Al alloy is as follows: Al3Sc, W phase, θ. The primary Al3Sc particles appear at the center of the α–Al grains and evidently acted as heterogeneous nucleating agents. Transmission electron microscopy shows that the nano-sized bean-like Al3Sc phase precipitated from the saturated solid solution. Moreover, the phase transition analysis of the 0.3–0.4Sc alloy during solidification shows that the formation of the W phase underwent two different types of reactions: the peritectic-eutectic reaction (L + Al3Sc → α–Al + W) and eutectic reaction (L → α–Al + W, L → α–Al + θ + W). The W phase formation mechanism of these two reactions is revealed through experiments. Simultaneously, W phases with different morphologies are observed in the 0.3–0.4Sc alloy, i.e., the W phase of the spherical-shell structure is formed by the peritectic-eutectic reaction, and the long strip W phase (~6 μm in size) is precipitated by the eutectic reaction.

Theprecipitate behavior, mechanical properties and corrosion behavior of an Al-Zn-Mg-Cu alloy during non-isothermal creep aging were investigated. The results show that diffraction patterns of GPI zones gradually disappear and those of &eta, &prime, phases are strengthened during the heating stage. More importantly, the size and volume fraction of precipitates increase with aging temperature increasing, which greatly enhances the mechanical properties of the alloy. The hardness and tensile strength of the alloy with H210 aging condition are 165 HV and 564 MPa, respectively. During the cooling stage, in addition to the diffraction pattern of &eta, phase, that of GPI zones can be observed again. Furthermore, the size of the precipitates decreases, and the volume fraction reaches a maximum. The hardness and tensile strength of the alloy with C120 aging condition reach 185 HV and 580 MPa, respectively. Furthermore, the characteristics of the grain boundary reveal that the width of precipitation free zones (PFZ) first increases during the heating stage and then decreases during the cooling stage. In the C120 condition, the newly generated secondary precipitates and the coarsening of undissolved precipitates around the grain boundary lead to the further narrowing of PFZ, but the coarse grain boundary precipitates (GBPs) are still not continuously distributed in the grain boundary. Hence, the alloy with C120 condition exhibits the most excellent corrosion resistance.

Electrical contact material's properties such as processability and switching behavior is strongly depend on the fabrication method. Here we present a study for evaluating the potential impact of fabrication technology for Ag/10SnO2 electrical contact materials. The result indicated that fabrication technology had an important influence on electrical contact physical phenomena, arc erosion morphology and arc erosion model of Ag/10SnO2 electrical contact materials. The mass change measured by volumetric method is 0.3765 mg larger than that of weighing method. In addition, the formation process and mechanism on arc erosion of Ag/10SnO2 electrical contact materials fabricated by different technology were discussed.

The influence of trace La on the oxidation of Ag-Sn alloy has been widely discussed. Here we present a detailed study for evaluating the potential impact of high content La for the oxidation of Ag-Sn alloy. We found that there are two kinds of intermetallic compounds in Ag-2Sn-4La alloy. The intermetallic compounds underwent a preferential oxidation, and the corresponded precipitation sequence of oxides was La2O3, La2Sn2O7 and SnO2. Based on the acquired insight, we suggest that high content La can accelerate the oxidation of Ag-Sn alloy oxidation but is not beneficial for the microstructure design of Ag-SnO2 electrical contact material.

Industrial application of superhydrophobic surfaces is often hindered by complicated process and sophisticated machines. A facile wet etching method (sandblast, HCl and sandblast/HCl) with vapor deposition of PFDS (1H, 1H, 2H, 2H-perfluorodecyltriethoxysilane) was applied to fabricate superhydrophobic surface of heat-resistant steel used for vane. The coating component, surface morphology and surface roughness parameters of sample were observed by attenuated total reflectance Fourier transform infrared spectroscopy, scanning electron microscopy and atomic force microscopy. Static water contact angle (WCA) of samples with and without PFDS coating was measured by contact angle goniometer. The results showed that WCA values of polished, sandblast, HCl and sandblast/HCl-etched samples are 98°, 97°, 100° and 101°, respectively, and increase to 112°, 148°, 151° and 154° after vapor deposition of PFDS. The sandblast/HCl-etched sample with PFDS coating shows higher superhydrophobicity because of very large surface roughness and lotus protrusion-like structure. The superhydrophobicity of this fabricated surface has no obvious change after 38 cycles of the film adhesion test, indicating excellent durability.

High-temperature plane-strain compression of a Ti-6Al-2Sn-4Zr-2Mo (Ti-6242) alloy with a lamellar structure was applied by a thermal simulation machine Gleeble 3800 at a temperature of 1223-1370 K and a strain rate of 0.01-10 s−1. Constitutive relations between the flow stress and strain at different temperatures and strain rates were constructed based on the Arrhenius equation. Processing maps based on the dynamic material model at strains of 0.5, 1.0, and 1.25 were also constructed to analyze the mechanism and instability of high-temperature deformation. Dynamic recrystallization was found to occur at 1223-1313 K and 0.01-0.1 s−1, with a peak efficiency of power dissipation of 70%. Observations of the microstructure demonstrated that α platelets and dynamic globularization were responsible for dynamic softening in the α + β phase field. Flow instability behaviors occurred at 1263-1343 K/1.78-10 s−1, 1233-1283 K/0.1-3.16 s−1, and 1353-1373 K/0.56-1.78 s−1, and adiabatic shear bands and microcracks were observed in these domains. Thus, for the lamellar Ti-6242 alloy, the recommended hot rolling parameters were 1243-1333 K and 0.01-0.1 s−1. Electron backscattered diffraction results revealed that the dynamic restoration mechanism in the β phase field was dynamic recovery when the strain rate was as high as 10 s−1.

The effects of Sc additions and isothermal aging on the microstructure and mechanical properties of 2055 aluminum alloy have been investigated. The isothermal aging temperatures investigated were 175 °C and 200 °C. Results show that the aging temperature does not affect the type of precipitates in both Sc-free and Sc-added 2055 Al alloys. While remarkable changes in the size and number density of T1 (Al2CuLi) precipitates have been observed. For samples aged at 175 °C for 8 h, the average length of T1 precipitates was increased from 39.9 nm to 45.6 nm, the number density decreased from 5.77 × 1022 m−3 to 3.68 × 1022 m−3 after Sc addition. On the contrary, when samples were aged at 200 °C for 8 h, the length decreased from 59.89 nm to 43.32 nm and number density increased from 2.13 × 1022 m−3 to 3.00 × 1022 m−3 by adding trace Sc. Slight deterioration of tensile strength and yield strength with higher ductility was founded at the aging temperature of 175 °C for 8 h due to the larger size and lower number density of T1 precipitates along with the formation of a W (AlCuSc) phase during the casting or homogenization processes. When aging temperature increased to 200 °C, tensile strength and yield strength were significantly improved by Sc addition without losing ductility. Highly dense fine T1 precipitates take responsible for the strength improvement, and to some extent it compensated the strength loss caused by the formation of W phase. A “vacancy-prison” mechanism was adopted to explain the effect of Sc additions on the precipitation of T1 phase as a function of aging temperature.

The morphological evolution of the stress-induced α″ martensite with increases in the stretching and rolling deformation degrees as well as the related orientation relationship were investigated in a β titanium alloy (Ti–19Nb–1.5Mo–4Zr–8Sn)·For a stretching deformation of 1%, the α″ martensite exhibited a packet morphology consisting of parallel lamellar structures. On the other hand, in the 2%-rolled sample, the α″ martensite exhibited a long lath-like distribution, which was accompanied by a few small pieces. With an increase in the deformation degree, the α″ martensite gradually exhibited a ladder-like structure consisting of long and short α″ laths or ellipsoids. The existence of these self-accommodating martensitic variants decreased the elastic energy. The parallel α″ laths present within a single packet were found to have the same orientation. The interface between the α″ and β phases was coherent, and their lattice constant relationships were identified as 2 a β ≈ b α ″ ≈ c α ″ and aβ ≈ aα″. Further, with the increase in the deformation degree, the hardness of the alloy first decreased and then increased; this was the case both the stretched as well as the rolled samples.

High-temperature compression deformation of a Zr-4 metal matrix with dispersed coated surrogate nuclear fuel particles was investigated at 750 °C–950 °C with a strain rate of 0.01–1.0 s−1 and height reduction of 20%. Scanning electron microscopy was utilized to investigate the influence of the deformation conditions on the microstructure of the composite and damage to the coated surrogate fuel particles. The results indicated that the flow stress of the composite increased with increasing strain rate and decreasing temperature. The true stress–strain curves showed obvious serrated oscillation characteristics. There were stable deformation ranges at the initial deformation stage with low true strain at strain rate 0.01 s−1 for all measured temperatures. Additionally, the coating on the surface of the surrogate nuclear fuel particles was damaged when the Zr-4 matrix was deformed at conditions of high strain rate and low temperature. The deformation stability was obtained from the processing maps and microstructural characterization. The high-temperature deformation activation energy was 354.22, 407.68, and 433.81 kJ/mol at true strains of 0.02, 0.08, and 0.15, respectively. The optimum deformation parameters for the composite were 900–950 °C and 0.01 s−1. These results are expected to provide guidance for subsequent determination of possible hot working processes for this composite. Keywords: Zr-4 metal matrix, Coated surrogate nuclear fuel particles, High-temperature deformation, Processing map, Microstructure