Microstructure and Mechanical Properties of Low-Density, B2-Ordered AlNbZrTix Multi-Principal Element Alloys

Low-density multi-principal element alloys (MPEAs) combining a high specific strength and considerable ductility have remained a research hotspot, due to their promising prospects for energy-saving industrial applications. Light Ti-containing AlNbZrTix (x = 1−3) MPEAs were designed and prepared by induction melting and annealing. As the Ti content increases, the microstructure of these MPEAs evolves from dual phase (B2-ordered and Zr5Al3-type structure) into a single-phase B2-ordered structure, while the density reduces by ~8.7%, from ~5.85 g·cm−3 (x = 1) to ~5.34 g·cm−3 (x = 3). Unexpectedly, the AlNbZrTix (x = 1, 2, 3) alloys possess high specific yield strengths of ~270 kPa·m3·kg−1, ~221 kPa·m3·kg−1, >208 kPa·m3·kg−1, along with excellent fracture strains of ~17.8%, 21.8%, and >50%, respectively. These combined compressive properties are superior to the reported data of most BCC/B2-dominant MPEAs. The deformation mechanism of the B2-ordered structure is explained as a dislocation-based mechanism, accompanied by antiphase domains. Here, the effect of Ti on the microstructure and compressive properties of AlNbZrTix MPEAs was investigated, providing scientific support for the development of advanced low-density materials

Microstructure and Mechanical Properties of Low-Density, B2-Ordered AlNbZrTi_x Multi-Principal Element Alloys

Low-density multi-principal element alloys (MPEAs) combining a high specific strength and considerable ductility have remained a research hotspot, due to their promising prospects for energy-saving industrial applications. Light Ti-containing AlNbZrTix (x = 1−3) MPEAs were designed and prepared by induction melting and annealing. As the Ti content increases, the microstructure of these MPEAs evolves from dual phase (B2-ordered and Zr5Al3-type structure) into a single-phase B2-ordered structure, while the density reduces by ~8.7%, from ~5.85 g·cm−3 (x = 1) to ~5.34 g·cm−3 (x = 3). Unexpectedly, the AlNbZrTix (x = 1, 2, 3) alloys possess high specific yield strengths of ~270 kPa·m3·kg−1, ~221 kPa·m3·kg−1, >208 kPa·m3·kg−1, along with excellent fracture strains of ~17.8%, 21.8%, and >50%, respectively. These combined compressive properties are superior to the reported data of most BCC/B2-dominant MPEAs. The deformation mechanism of the B2-ordered structure is explained as a dislocation-based mechanism, accompanied by antiphase domains. Here, the effect of Ti on the microstructure and compressive properties of AlNbZrTix MPEAs was investigated, providing scientific support for the development of advanced low-density materials

The effect of grain size on the annealing-induced phase transformation in an Al0.3CoCrFeNi high entropy alloy

The annealing-induced phase transformation was investigated in coarse-grained and severely deformed nanocrystalline face-centered cubic (FCC) high entropy alloys (HEA). Increasing temperature leads to phase transformations from the FCC phase to an L12 phase and finally to a B2 phase in the coarse-grained HEA. By contrast, direct transformation from the FCC phase to the B2 phase was observed in the nanocrystalline HEA at a lower temperature

GPa grade cryogenic strength yet ductile high-entropy alloys prepared by powder metallurgy

The carbon-doped Fe50Mn30Co10Cr10 HEAs with excellent cryogenic mechanical properties were prepared by powder metallurgy, and their tensile deformation behavior and strain-hardening mechanism were investigated. The yield strength of the HEAs at 77 K improved from 489.7 to 1087.0 MPa as the carbon content increased from 0 to 3 at. %, which mainly stems from the increased lattice friction caused by the addition of carbon and the cryogenic environment; the ultimate tensile strength of the HEAs doped with 2 and 3 at. % carbon reached 1.2 and 1.4 GPa, respectively, while the elongation to fracture reached 31.6 % and 16.8 %, respectively, which is mainly attributed to the joint activation of microbands, twinning, and HCP phase. The deformation mechanism gradually changed from deformation-induced phase transformation to microbands and twinning with increasing carbon content under cryogenic conditions. This study provides a meaningful reference for the design and development of powder metallurgy HEAs with excellent performance in cryogenic applications

Smoking and smoking cessation in relation to risk of diabetes in Chinese men and women: a 9-year prospective study of 0·5 million people

Summary: Background: In developed countries, smoking is associated with increased risk of diabetes. Little is known about the association in China, where cigarette consumption has increased (first in urban, then in rural areas) relatively recently. Moreover, uncertainty remains about the effect of smoking cessation on diabetes in China and elsewhere. We aimed to assess the associations of smoking and smoking cessation with risk of incident diabetes among Chinese adults. Methods: The prospective China Kadoorie Biobank enrolled 512 891 adults (59% women) aged 30–79 years during 2004–08 from ten diverse areas (five urban and five rural) across China. Participants were interviewed at study assessment clinics, underwent physical measurements, and had a non-fasting blood sample taken. Participants were separated into four categories according to smoking history: never-smokers, ever-regular smokers, ex-smokers, and occasional smokers. Incident diabetes cases were identified through linkage with diabetes surveillance systems, the national health insurance system, and death registries. All analyses were done separately in men and women and Cox regression was used to yield adjusted hazards ratios (HRs) for diabetes associated with smoking. Findings: 68% (n=134 975) of men ever smoked regularly compared with 3% (n=7811) of women. During 9 years' follow-up, 13 652 new-onset diabetes cases were recorded among 482 589 participants without previous diabetes. Among urban men, smokers had an adjusted HR of 1·18 (95% CI 1·12–1·25) for diabetes. HRs increased with younger age at first smoking regularly (1·12, 1·20, and 1·27 at ≥25 years, 20–24 years, and <20 years, respectively; p for trend=0·00073) and with greater amount smoked (1·11, 1·15, 1·42, and 1·63 for <20, 20–29, 30–39 and ≥40 cigarettes per day; p for trend<0·0001). Among rural men, similar, albeit more modest, associations were seen. Overall, HRs were more extreme at higher levels of adiposity. Among men who stopped by choice, there was no excess risk within 5 years of cessation, contrasting with those who stopped because of illness (0·92 [0·75–1·12] vs 1·42 [1·23–1·63]). Among the few women who ever smoked regularly, the excess risk of diabetes was significant (1·33 [1·20–1·47]). Interpretation: Among Chinese adults, smoking was associated with increased risk of diabetes, with no significant excess risk following voluntary smoking cessation. Funding: Wellcome Trust, Medical Research Council, British Heart Foundation, Cancer Research UK, Kadoorie Charitable Foundation, Ministry of Science and Technology, National Natural Science Foundation of China, and China Scholarship Council