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Abstract The long-term hydrogen storage performance of a CaCu 5 -type LaNi 4 Co alloy is studied by detailed analysis of its P-C-T curves and structural changes within 1000 cycles. The alloy shows one absorption plateau (α→β phase transition) and two desorption plateaus (γ→β and β→α phase transitions). With increasing cycle number, the plateau pressures for both α→β and β→α phase transitions decrease due to the increase in cell volumes. The increased crystal cells also provide more space to accommodate the simultaneous occupations of 12° and 6 m sites, and thus β→α and β→γ desorption plateaus become less distinguishable. During cycling, partial phase decomposition, crystal grain destruction and surface oxidation occur, resulting in the loss of hydrogen storage capacity. In addition, due to the increase in the atomic disorder and internal microstrains and defects, the average slope factors (SF / H %) of the hydrogen absorption/desorption plateaus are increased. Particularly, the SF / H % value of the γ→β plateau is always higher than those of the α→β and β→α plateaus, and it also increases faster with cycling, reaching about 4 times of the other two plateaus at the 1000th cycle. It is considered that the improvement of the γ→β phase transition process is significant to promote the cycling behavior and practical applications of this alloy system. Graphical abstract Image 1 Highlights • Hydrogen storage properties of the LaNi 4 Co alloy within 1000 cycles are studied. • Changes in PCT curves with double desorption plateaus are investigated in detail. • Phase decomposition, lattice expansion, crystal damage and surface oxidation occur. [ABSTRACT FROM AUTHOR]

LaNi 5 -based hydrogen storage alloys have a strong application potential in many areas such as gaseous hydrogen storage, hydrogen compressing, Ni/MH batteries etc. But the cycling stability is always an important issue of concern. In this study, the changes in the hydrogen storage performance of the LaNi 4 Al alloy at 403, 423 and 443 K during 1000 hydrogen absorption/desorption cycles are studied, and the degradation mechanism is explored using EXAFS as a main study method. It is found that with increasing cycle number, the P-C-T plateau first becomes flattened then steepened, the plateau pressure and the hysteresis are decreased, the entropy change for both hydrogen absorption and desorption first increases and then decreases, and the hydrogen storage capacity decreases. Testing temperature does not have notable influence in the variation trend of the long-term hydrogen storage properties. The degradation is mainly reflected by the tilted P-C-T plateau and the reduced hydrogen storage capacity. Structural analysis results suggest that the strain-induced nanocrystalization and the atomic mis-location during hydrogen absorption/desorption might cause a high disorder state and a partial destruction in LaNi 5 crystal lattice, resulting in the degradation in the hydrogen storage properties. [ABSTRACT FROM AUTHOR]

• Mn-Cu alloys are fabricated by laser powder bed fusion based on mixed element powders. • The optimal processing windows for the dense Mn-Cu alloys is discovered. • The as-fabricated Mn-Cu alloys present good tensile properties. Mn-Cu alloys with high Mn contents have good damping capacity but poor workability and mechanical properties. In this research, laser powder bed fusion (LPBF) was applied to fabricate the Mn-Cu alloys (Mn 63 Cu 37 , Mn 73 Cu 27 , and Mn 82 Cu 18) based on mixed element powders. The printability, microstructure and mechanical properties of the as-fabricated Mn-Cu alloys were investigated through a series of characterization methods. The results indicate that the Mn-Cu alloys with high relative densities (99.76–99.85%) can be fabricated using the optimal processing parameters. The as-fabricated Mn-Cu alloys show higher strengths (537.5–589.6 MPa) and yield strengths (404.0–440.1 MPa) than those of commercial Mn-Cu alloys fabricated by conventional methods. The tensile strength presents an overall downward trend with increasing Mn content. Thus, LPBF can be considered as a promising method to fabricate Mn-Cu alloys with high Mn contents. [ABSTRACT FROM AUTHOR]

The microstructure and properties of Cu-0.42Cr (wt.%) and Cu-0.45Cr-0.14Ti (wt.%) alloy subjected to cold rolling and aging treatment are investigated through tensile testing, electrical conductivity measurement, scanning electron microscopy, and transmission electron microscopy. Results show that the tensile strength of Cu-0.45Cr-0.14Ti (wt.%) alloy enhances as the degree of deformation increases, but the degree of deformation slightly influences electrical conductivity. When deformation is changed, electrical conductivity is basically unchanged. The good combination of strength and electrical conductivity, which reach 610 MPa and 55.4% IACS, respectively, can be obtained in the Cu-0.45Cr-0.14Ti (wt.%) alloy after 80% cold rolling and aging at 450 °C for 15 min. Ti inhibits the growth of the Cr precipitation phase and enhances the precipitation strengthening effect. Ti mainly exists in the matrix in the form of solute atoms, which do not form a separate lattice structure after aging treatment. • The alloy material is prepared by a process method combining solid solution aging treatment and deformation treatment. • Ti element enhances the effect of age hardening and significantly improves the mechanical properties of the alloy. • Titanium atoms segregate around the Cr phase to slow down the rate of precipitation coarsening. • Ti atoms have never formed a separate lattice structure in the Cu-0.45Cr-0.14Ti (wt.%) alloy. [ABSTRACT FROM AUTHOR]

Rare earth–Mg–Ni-based alloys with superlattice structures are novel anode materials for nickel metal hydride batteries, wherein A 5 B 19 -type alloys have been regarded as the replacement of the current commercialized A 2 B 7 -type alloys due to the superior discharge ability at high rates and cycling stability. However, it is still a challenge to further improve the hydrogen storage properties of the A 5 B 19 -type alloys in a low-cost approach. Herein, we select low-cost Mn and Fe elements to substitute Ni to further reduce the cost of an A 5 B 19 -type La 0.72 Y 0.13 Mg 0.15 Ni 3.70 Al 0.15 alloy and focus on their effects on the alloy's structure and hydrogen storage properties. Results show that the La 0.72 Y 0.13 Mg 0.15 Ni 3.65 Al 0.15 Fe 0.05 alloy features increased intrinsic gas-solid hydrogen storage ability of 1.44 wt% and hydrogen absorption enthalpy change of −22.9 kJ mol–1, which have been altered by 0.21 wt% and 7.3 kJ mol–1 in contrast to the La 0.72 Y 0.13 Mg 0.15 Ni 3.70 Al 0.15 alloy, respectively. Furthermore, the Fe substitution benefits capacity retention during electrochemical cycling compared to Mn, which maintains 87.5% and 62.4% after cycling 100 and 500 times. The Mn substitution results in superior rate capability compared to the alloy containing Fe. The work provides guidance for designing hydrogen storage alloys with superlattice structures to improve the electrochemical performance. • Pr 5 Co 19 -type alloys with low cost Mn and Fe substituted Ni are obtained. • Effect of Mn and Fe substituted Ni on hydrogen storage properties is clarified. • Fe substituted Ni increases hydrogen storage capacity from 1.23 wt% to 1.44 wt%. • Fe substitution rises the capacity retention from 52.6% to 62.4% at the 500th cycle. • Mn substitution optimizes the discharge ability at high rates. [ABSTRACT FROM AUTHOR]

• The oxidation behaviors of Zr-Sn-Nb and Zr-4 alloy were investigated under three ambients in the range of 650–1250 ℃. • The kinetics transitions for Zr-Sn-Nb and Zr-4 alloy under three test ambients were obtained and analyzed. • The break-away of oxide layer resulting from the martensite phase transformation of from t-ZrO 2 to m-ZrO 2 was clearly observed. • A multi-layer structure of oxide-nitride-oxide was found in air ambient caused by the re-oxidation of ZrN. • The effects of crack formation of oxide layer on oxidation resistance in various scenarios were studied. Zirconium-based alloys are widely used for fuel claddings particularly in pressurized water reactor. This study investigates the oxidation characteristics of Zr-4 and Zr-Sn-Nb alloy in steam, oxygen and air atmosphere respectively in temperature range of 650–1250 ℃ by a modified thermo-gravimetric analyzer. The oxidation rate exponents and oxidation kinetic correlations are calculated. The rate transitions of the kinetic oxidation for Zr-Sn-Nb and Zr-4 occur both at 1100 ℃ in steam, both 950 ℃ in air, and 1200 ℃ and 1150 ℃ in oxygen, respectively. The oxidation kinetics of both zirconium alloys in air is faster than in steam and oxygen. The maximum thickness of the oxide layers for both zirconium alloys is reached at 1150 ℃ in steam due to the phase transformation of the zirconium from monoclinic to tetragonal. The oxide layer formed in air is porous, heterogeneous with a multi-layer structure of oxide-nitride-oxide because of the formation and re-oxidation of zirconium nitride in oxygen starvation environment. The oxidation resistance of the zirconium alloy is related to the integrity and compactness of the oxide layer. Gas diffusion through the imperfection in the oxide scale may accelerate subsequent oxidation. [ABSTRACT FROM AUTHOR]

In this work, the microstructure and hydrogen storage properties of Ti 1- x Ce x V 0.45 Mn 1.5 (x = 0, 0.05, 0.10, 0.15, and 0.20) alloys have been studied. It shows that the x = 0 alloy consists of a C14 Laves single phase. Moreover, alloys containing Ce can exhibit the CeO 2 phase, whose content rises as Ce content does. Furthermore, CeO 2 phase aggregation causes the alloy to fracture and the hydrogen diffusion channel to enlarge. According to the PCT curves (25 °C), the plateau pressure increases with increasing Ce content, and the hydrogen storage capacity decreases with increasing Ce content due to increase in Ce content which does not absorb hydrogen. And it is also found that increase in Ce substitution for Ti results in better dynamic properties for the alloys. And the dehydrogenation kinetics curves show that hydrogen desorption rate substantially increases with x getting larger. This is because CeO 2 phase acts as the "hydrogen pump" to increase the rate of hydrogen discharge in the alloy, The fastest hydrogenation kinetics are shown, the best hydrogen storage performance is achieved, and the ma x imum hydrogenation is reached in less than 100 s. • According to the PCT curves, the plateau pressure increases with increasing Ce content and the hydrogen storage capacity decreases with increasing Ce content. • In this study, CeO 2 phase acts as the "hydrogen pump" to increase the rate of hydrogen discharge in the alloy. • CeO 2 phase aggregation leads to cracks in the alloy. [ABSTRACT FROM AUTHOR]

The 2195 Al-Cu-Li alloy is widely utilized in the aerospace industry due to its lightweight nature and high strength. Consequently, gaining a comprehensive understanding of techniques to enhance its microstructural and mechanical properties is crucial for the consistent production of reliable and high-strength aerospace components. In this investigation, a pristine 2195 industrial ingot was subject to three distinct forging pretreatments: PT1, which involved a direct three upsetting and three stretching (3U3S) process; PT2, which combined double stage homogenization (DH) with 3U3S; and PT3, which involved DH along with six upsetting and six stretching (6U6S). Subsequent warm deformation and T8 aging treatment were applied to the pretreated forgings. The microstructure evolution during the processes and the final mechanical properties in three orthogonal dimensions were examined. The findings revealed that the combination of DH and multi-dimensional forging (MDF) facilitated the dissolution of non-equilibrium phases to a greater extent. Consequently, the main strengthening phase transformed from the T 1 + δ' phase observed in PT1 to the denser T1 + little θ' phase observed in PT2 and PT3 after T8 aging treatment. Notably, the tensile strength and yield strength of PT2 and PT3 specimens increased by 20–30 MPa in all three directions. Moreover, the MDF process accelerated the recrystallization behavior from PT1 to PT3, resulting in a gradual reduction in the average grain size of the pretreated samples from 356 µm to 186 µm. Following warm forging and T8 aging, the grains exhibited a finer and equiaxed structure. Additionally, the coarse phase was identified as the primary source of transgranular cracking. The coarse phases within the matrix became more homogeneous and finer from PT1 to PT3, with a gradual decrease in their area fraction. On the fracture surfaces, the aggregation of coarse phases diminished. Consequently, the elongation in the z-direction improved, and the elongation anisotropy and standard deviation decreased in all three directions for PT3 specimens. The findings presented in this study provide valuable insights into the high-performance manufacturing of Al-Cu-Li alloys. • The DH and doubling the strain of MDF both promoted the dissolution of non-equilibrium phases. • Combine DH treatment with MDF enhanced the precipitation kinetics of the T 1 phase, increasing the strength by 20–30 MPa. • The coarse phase was the main transgranular cracking sources, which was diminished gradually by the improved process. [ABSTRACT FROM AUTHOR]

In this study, the role of tantalum (Ta) on the phase transformation, microstructure evolution, mechanical properties and corrosion resistance of titanium-tantalum (Ti–Ta) alloys in-situ fabricated via selective laser melting (SLM) was investigated. Ti–Ta mixed powders with different Ta ratios ranging from 0 to 25 wt % were prepared by ball milling for the SLM process. With the increase of Ta content, the SLM-processed Ti–Ta alloys exhibits the microstructure evolution from the lath α grain to acicular α' + primary cellular β grains, accompanying with the gradual suppression of martensite transformation. The β-stabilized effect of Ta promotes the formation of β (Ti, Ta) solid solution phase in the alloys. The rise of Ta addition in SLM-processed Ti–Ta alloys contributes to the improvement on the tensile strength from 641 to 1186 MPa and the microhardness from 257 to 353 HV, which results from a combined effect of grain refinement strengthening and the solid solution strengthening. The Young's modulus decreases from 115 to 89 GPa due to the increasing amount of β phase. Additionally, the corrosion resistance of the Ti–Ta alloys is enhanced with few pits on the surfaces due to the increasing amount of Ta 2 O 5 identified through X-ray photoelectron spectroscopy. These findings provide the knowledge and boost the further understanding on the SLM-processed Ti–Ta alloys as promising candidates for biomedical application. • Ti–Ta alloys were fabricated by SLM with different Ta contents (0–25 wt %). • The microstructure evolves from the lath α to acicular α' + primary cellular β. • Ta addition leads to the improvement on the tensile strength and the microhardness. • The enhanced corrosion resistance is related to the composition of the passive film. [ABSTRACT FROM AUTHOR]

The 2195 Al-Cu-Li alloy is widely utilized for the fabrication of key aerospace vehicle components; hence, an in-depth understanding of its hot deformation behavior is essential for consistently achieving high-performance products. In this study, isothermal compression tests were performed on 2195 Al-Cu-Li alloy ingots in the temperature and strain rate ranges of 250–500 °C and 10−3-1 s−1, respectively. A processing map was established to predict the workability under different conditions. The corresponding microstructures were examined to reveal their hot deformation mechanism. Results demonstrated that the processing map was divided into four distinct domains. The unstable zone was located in the 250–375 °C/10−1.5-1 s−1 and 250–275 °C/10−2.5–10−1.5 s−1, temperature/strain rate regimes, in which deformation bands and flow localization were observed. The deformation bands blocked dislocations and compromised the dynamic recrystallization (DRX) behavior, hence damaging the microstructure. Further, large coarse T 1 phases precipitated in the 325–410 °C/10−2.5–10−3 s−1 regime, which led to the formation of heterogeneities in the microstructure, corresponding to a minimum workability in the processing map. The optimal hot-working domain for the 2195 alloy was determined to be 460–500 °C/10−3–10−2 s−1, and the dominating hot deformation mechanisms were DRX and dynamic recovery (DRV). Specifically, continuous and discontinuous DRX behaviors dominated in the 300–400 °C/10−3 s−1 and 450–500 °C/10−3 s−1 regimes, respectively. DRX gradually weakened as the strain rate increased at 500 °C. Further, the weakening of DRX was only minimally affected by temperature at 400–500 °C during high-speed deformation (1 s−1). The results reported herein can provide valuable insights into the hot working of Al-Cu–Li alloys. • A processing map (PM) was established to accurately predict the hot deformation behavior of the 2195 alloy. • Deformation bands and flow localization were the main microstructure response in the unstable domain. • Large coarse T 1 phases precipitated in the precipitation sensitive domain, leading to heterogeneity deformation. • The optimal hot working domain was 460–500 °C/10−3–10−2 s−1, which was dominated by DRX and DRV. • Within the 300–400 °C/10−3 s−1 regime, CDRX was the main DRX mechanism, whereas DDRX predominant at 450–500 °C/10−3 s−1. [ABSTRACT FROM AUTHOR]

The microstructure, phase composition, tensile and fatigue properties of Ti–6Al–4V samples produced by selective laser melting (SLM), SLM followed by heat treatment (HT), and SLM followed by hot isostatic pressing (HIP) were investigated to explore a simpler approach to improve the mechanical performances by post treatment at minimum cost in our work. Results showed that the tensile and fatigue properties of the as-SLMed samples were far below the level of wrought counterpart. Heat treatment and HIP can more obviously enhance tensile properties and fatigue performances, respectively. The microstructure consisted of the lamellar or acicular α and grain boundary α within prior β columnar grain boundaries in the SLMed samples after solution treatment at 850 °C followed by water quenching, whose tensile properties were improved to be 1085 MPa, 859 MPa, 14.0%. A tri-modal microstructure including lamellar α, polygonal α and acicular nanoscale α+β phase formed in the samples after 850 °C solution treatment and 550 °C aging treatment. Their corresponding tensile properties were enhanced to be 1192 MPa, 1054 MPa, 11.4%. The microstructure was composed of lamellar α+β phases for the SLMed sample after HIP treatment, which improved the tensile (>1000 MPa, >850 MPa, and >10%) and fatigue (105∼6 at the stress amplitude of 500 MPa) properties. Therefore, solution treatment at 850 °C followed by water quenching or HIP treatment is a simpler method to control the performances of the SLMed Ti–6Al–4V alloy. • Tensile and fatigue properties of SLMed Ti–6Al–4V alloy are below those of wrought ones. • 850 °C solution treatment inherits advantages and eliminates defects of SLM, resulting in better tensile properties. • Tri-modal microstructure forms after 850 °C solid-solution and 550 °C aging treatments. • HIP treatment improves the tensile and fatigue properties, independent of SLM processing parameters. • Heat treatment can adjust tensile properties, while HIP can enhance fatigue performance. [ABSTRACT FROM AUTHOR]

Selective laser melting (SLM) is used to fabricate near-equiatomic NiTi alloy from Ni–Ti mixed element powders. The influence of energy input on formability, microstructure, phase transition and shape memory effect of the NiTi alloy (atomic ratio is 1:1) is studied. The results show that the as built specimens contain NiTi phase and stable phase transition. The macro-defect-free NiTi alloys can be built up well from 118.75 J/mm3 to 750 J/mm3. The width of the columnar NiTi phase and the amount of the equiaxed NiTi phase increase while the fraction of NiTi phase decreases with the increase of the energy input. The B2↔B19′ phase transition behavior enhances with the increase of the energy input. And the as built NiTi alloy fabricated at high energy input presents better shape memory effect (SME), its recoverable strain is about 5.17% under a pre-strain of 6%, which is close to those by conventional methods. Thus, SLM from mixed element powders can be regarded as a promising processing method to manufacture the NiTi alloy. • A NiTi alloy is fabricate by selective laser melting from mixed element powders. • The range of energy input for the macro-defect-free NiTi alloys is discovered. • The relation between the forming quality and the dimensional accuracy is discovered. • The effect of laser energy input on the microstructural evolution is studied. • NiTi alloys built at higher energy input prefers to get better shape memory effect. [ABSTRACT FROM AUTHOR]