Search

The Ti-7Al-1Mo-0.5V-0.1C alloy exhibits low density and good mechanical properties, and has potential applications in aerospace industries. The microstructure features of titanium alloys, such as the morphology and volume fraction of the primary α phase (αp) and the precipitation of the secondary α phase (αs), are sensitive to heat treatment parameters, especially the cooling rate from the two-phase region. In this work, we have characterized the precipitation of the secondary α phase and ordered α2 phase in Ti-7Al-1Mo-0.5V-0.1C alloy under water quenching, air cooling, and furnace cooling, and have investigated their effects on the mechanical properties of the Ti-7Al-1Mo-0.5V-0.1C alloy. The results show that the secondary α phase is significantly coarsened in the air-cooled alloy and leads to an increase in the strength but decrease in the ductility of the alloy, while the equiaxed microstructure generated in the furnace-cooled alloy, with no precipitation of the secondary α phase and an increase in size of the ordered α2 precipitation phase within the primary α phase, contributes to a further increase in ductility. [ABSTRACT FROM AUTHOR]

(100‐x) wt.% La0.9Sr0.1 Ga0.8Mg0.2O2.85 ‐ x wt.% Ce0.8Gd0.2O1.9 (x = 0, 5, 10, 20) electrolytes were prepared by solid‐state reaction. The composition, microstructure, and electrical conductivity of the samples were investigated. At 300 ~ 600°C, the pure La0.9Sr0.1 Ga0.8Mg0.2O2.85 electrolyte has a higher conductivity compared to the composite electrolytes, but at 650 ~ 800°C the 95 wt.% La0.9Sr0.1 Ga0.8Mg0.2O2.85 ‐ 5 wt.% Ce0.8Gd0.2O1.9 composite electrolyte presents the highest conductivity, reaching 0.035 S cm−1 at 800°C. The cell performances based on La0.9Sr0.1 Ga0.8Mg0.2O2.85‐Ce0.8Gd0.2O1.9 electrolytes were measured using Sr2CoMoO6‐La0.9Sr0.1 Ga0.8Mg0.2O2.85 as anode and Sr2Co0.9Mn0.1NbO6 ‐La0.9Sr0.1 Ga0.8Mg0.2O2.85 as cathode, respectively. At 800°C, the measured open‐circuit voltages are higher than 1.08 V, and the maximum power density and current density of the fuel cell prepared with 95 wt.% La0.9Sr0.1 Ga0.8Mg0.2O2.85 ‐ 5 wt.% Ce0.8Gd0.2O1.9 electrolyte reach 192 mW cm−2 and 720 mA cm−2, respectively. [ABSTRACT FROM AUTHOR]

Abstract Twin-twin interactions form twin-twin boundaries (TTBs) which can prevent twin propagation, inhibit direct twin transmission, retard detwinning, and facilitate secondary twins. The current work studies the microstructure and interaction mechanisms of non-cozone twin-twin junctions by combining electron back-scatter diffraction observations and atomistic simulations. Non-cozone twin-twin interactions are defined as the intersecting line of the two twins isn't parallel to one < 1 2 ¯ 10 > zone axis (a-axis) and include two types, Type II(a) (T 2 → T 1) and Type II(b) (T 3 → T 1), according to the crystallography of two interacting twins. For Type II(a) interaction, both statistical results of experimental observations and interfacial energy calculation confirm TTB formation on the obtuse side of the incoming twin instead of the acute side. However, for Type II(b) interaction, the growth of twins on both sides is impeded, although the TTB on the acute side possesses the lowest interfacial energy. Atomistic simulation demonstrates that, for Type II(a) twin-twin interactions, positive resolved shear stresses on the obtuse side favor T 1 and T 2 twinning, while negative resolved shear stresses on the acute side impede T 1 and T 2 twinning. For Type II(b), negative resolved shear stresses on both the acute and obtuse sides result in impediment of twinning on both sides. These results can be used in developing micro/macro-scale predictive models that deal with the role of multiple twins and twin variants during mechanical processing. The analytical and simulation methods can be generalized and applied to atomistic analysis in different material systems to further explain the hardening mechanisms associated with twin-twin interactions. Graphical abstract Image 1 [ABSTRACT FROM AUTHOR]

Microstructure and nanoindentation properties of the mouthparts for the skillful driller Cyrtotrachelus longimanus are presented. The composition and morphological examinations are made using light, fluorescent, scanning electron microscopy, and Energy Disperse Spectroscopy, respectively. Nanoindentation was carried out to measure the elastic modulus and the hardness of mouthparts. The hardness and modulus for 'dry' samples is 0.202 ± 0.065 and 8.604 ± 0.838 GPa, respectively, and the values of 'fresh' ones is 0.126 ± 0.0196 and 6.951 ± 0.065 GPa, respectively. These results are critical for analyze the drilling mechanism of the weevil and provide a biological template to inspire the biomimetic design. [ABSTRACT FROM AUTHOR]

The microstructure, composition and mechanical properties of the rostrum inCyrtotrachelus longimanus(JHC Fabre) were studied utilizing light, fluorescent, scanning electron microscopy (SEM) and energy-dispersive spectroscopy. SEM images show the morphological characteristics of rostrum’s cross section; it is a typical lightweight multilayer structure – one rigid exocuticle layer and dense endocuticle layers, which construct unevenly overlapping fiber structures. The composition analysis of the rostrum shows that it is mainly composed of C, H, N, O, as well as some metal elements and microelements, such as Mg, Si, Zn, Ca and Na, which contribute to its mechanical performance. The mechanical properties of the rostrum were tested by the electronic universal testing machine, which shows it has high-specific strength and is almost the same as that of the stainless steel. The results may provide a biological template to inspire biomimetic lightweight structure design. [ABSTRACT FROM PUBLISHER]

In the referenced article, the corresponding authors should be Danfeng Pan (pdf@nju.edu.cn) and Linwei Yu (yulinwei@nju.edu.cn). [ABSTRACT FROM AUTHOR]

To realize strength-ductility balance in a novel titanium alloy Ti–6Mo-3.5Cr–1Zr, the microstructure transition of stress-induced β→ω was intendedly retarded by design of α-β hybrid structure. The outstanding quasi-static tensile properties with yield strength of ∼825 MPa, true tensile strength of ∼1171 MPa and total elongation of ∼29.7% was obtained via microstructure optimization. [Display omitted] • α" phase transformation is suppressed for improving yield strength in the material. • The SIω transformation is intendedly retarded by design of α-β hybrid structure. • Excellent strength-ductility balance is achieved via microstructure optimization. [ABSTRACT FROM AUTHOR]

The dual-hardness titanium alloy laminated composites exhibit high hardness and toughness, making it an ideal material for applications in ballistic protection, wear-resistant and other fields. However, the substantial difference in hardness poses a challenge in effectively bonding these alloys, potentially resulting in the emergence of cracks and a decrease in bonding strength. In this study, a new Ti 5 Si 3 -reinforced high-hardness Ti311 (475 HV) and TC4 (352 HV) titanium alloys were successfully combined by hot-pressing diffusion bonding. The synergy effects of hot-pressing temperature and deformation on the microstructural evolution and mechanical properties of the Ti311/TC4 interface were systematically studied. The metallurgical bonding interface was formed at 850 °C under 25 MPa of 15.9% deformation, with the maximum shear strength value of 606 MPa. Moreover, a continuous and discontinuous coupled dynamic recrystallization mechanism was revealed. Deformed α grains were transformed to fine recrystallized grains, and gradually grew with the help of continuous dynamic recrystallization to eliminate the original flat interface. In addition, with the occurrence of element diffusion, the interface between Ti311 and TC4 is ultimately successfully bonded. Notably, the Ti 5 Si 3 phase played a double-edge sword effect on bonding the Ti311/TC4 interface, promoting the occurrence of continuous dynamic recrystallization of adjacent α phase in TC4, but having negative effects on element diffusion. • Ti311/TC4 laminated composites with significant hardness difference but high shear strength were fabricated. • The synergy effects of temperature and deformation on the T311/TC4 interface were elaborated. • Continuous and discontinuous recrystallization were found to jointly promote the interface bonding. • Ti 5 Si 3 on the interface promotes dynamic recrystallization but hinders element diffusion. [ABSTRACT FROM AUTHOR]

Hierarchical microstructure (HM) shows excellent comprehensive properties, but the relationship between mechanical properties and HM characteristics is not clear. In this work, seven HMs of Ti20C were tailored by aging treatments, containing equiaxed α (α ep), lamellar α of micron and submicron scale (α lp-i , α lp-ii) and transformed β t (with nano-scale precipitated phases ω/α s in β). Different combinations of strength and plasticity were achieved. It was found that, the different phase interfaces hindered dislocation transferring, and ω/α s phase restricted dislocation movements in β t , which resulted in strength improvement. Moreover, HM was quantitatively characterized, then the relationship between HM characteristics and yield strength (R p0.2), elongation after fracture (A) was precisely deciphered by referring to Hall-Petch formula and mixing law. It was found that the influence of β t , α lp-ii , α ep and α lp-i on R p0.2 decreased orderly. The decrease in the thickness of α lp-ii and increase in the volume fraction (VF) of β t , α lp-ii , were the most effective methods to improve R p0.2. For A, the VF of β t was negatively correlated with it, but the equivalent circle diameter (ECD) of α ep and the thickness of α lp-i , α lp-ii were positively correlated with it. Specifically, α ep and α lp-ii had a higher contribution to plasticity than α lp-i , and the increase in the ECD (or thickness) and VF of α ep and α lp-ii was most beneficial to improve plasticity. • Hierarchical microstructures containing α ep , α lp-i , α lp-ii and β t (β + ω/α s) phases by aging were induced. • Wide range of strength and plasticity was achieved by tailoring microstructures. • Quantitative relationship between microstructure and tensile properties (R p0.2 , A) was precisely deciphered. • The influence of β t , α lp-ii , α ep and α lp-i on yield strength was found to decrease orderly. • Size and content of α ep , α lp-i and α lp-ii was beneficial for the elongation, while β t was adverse. [ABSTRACT FROM AUTHOR]

In this paper, Mg-Al-Ca-Mn-Cu magnesium alloys by Cu alloying were studied with the aim of developing Mg alloys with higher heat conduction. As a result, the mechanical properties and thermal conductivity of the alloys was evaluated simultaneously, owing to the addition of Cu, which meets the requirements of the project to develop high-strength and high-conductivity magnesium alloy. Compared with the commercial AZ31 magnesium alloy, the strength and plasticity are improved by means of fine grain strengthening. Meanwhile, the amount of solid solution atoms in the alloy decreases, and the content of the second phase particles increases, which reduces the degree of lattice distortion. On the other hand, the Cu element provides a large amount of free electron for heat transfer, which makes the alloys have a high thermal conductivity. • The microstructure and morphology characteristics of the Mg-Al-Ca-Mn magnesium alloy by Cu alloying were investigated. • Cu addition improved the mechanical properties and thermal conductivity of the Mg-Al-Ca-Mn alloy. • The microstructure evaluation during the extrusion processing effected by the addition of Cu content was investigated. [ABSTRACT FROM AUTHOR]

The stress-induced α" phase transformation in titanium alloys has received extensive attention due to its significant effect on mechanical properties. In this work, by adjusting the heat treatment process, the stress-induced α" phase transformation is activated in Ti-5Al-2.5Cr-5Mo-1Sn. The quasi-static tensile mechanical properties of the alloy under air-cooled and as-quenched states have been compared. Further, the morphology and orientation of the stress-induced α" phase and its interaction with dislocations are investigated by X-ray diffraction (XRD), optical microscope (OM), electron backscattered diffraction (EBSD) and transmission electron microscope (TEM) experiments. The value of average misorientation at the stress-induced α" bands region is larger than that in the β matrix, which indicates that the degree of plastic deformation in the stress-induced phase transformation region is higher. Therefore, the stress-induced α" phase exhibits a strong strain partitioning effect during the stretching process and improves the ductility of the material. The β/α" interface has a weak effect to hinder the dislocations, which results in low tensile strength of the alloy. This work can provide insight into the influence of stress-induced α" phase transformation on the mechanical properties of transformation induced plasticity (TRIP) type titanium alloys. • The Ti-5Al-2.5Cr-5Mo-1Sn alloy is elaborately regulated to produce TRIP effect. • Average misorientation of α" band region is generally larger than that of β matrix. • α" phase exhibits a strong strain partitioning effect to increase alloy ductility. • The β/α" interface is semi-coherent and has a weak effect to hinder dislocations. [ABSTRACT FROM AUTHOR]

A novel metastable β-type Ti–6Mo-3.5Cr–1Zr alloy is designed using d-electrons theory to introduce diverse phase transformations. Stress-induced ω (SIω) phase transformation dominates the initial deformation, while the SIω bands are transformed to α+β phase as the strain increases. The sequential mechanism associated with β→SIω→α+β is first reported in titanium alloys. • A novel metastable β alloy Ti–6Mo-3.5Cr–1Zr is designed using d-electrons theory. • The stress-induced β.→ω→(β+α) phase transformation is firstly reported • Localized growth and combination of the single athermal ω variant form the SIω. • Elemental redistribution occurs during the stress-induced ω.→(β+α) process • The covalent bond gradually dominates during the β.→ω→α transformation [ABSTRACT FROM AUTHOR]