Cu-Cr-Zr alloy, a copper-based precipitation hardened alloy with good electrical and thermal conductivities and moderate strength at elevated temperatures, is being considered for many advance ...technological applications including fusion energy programme. Ageing study on indigenously manufactured Cu-Cr-Zr alloy (0.7-0.8 wt.% Cr, 0.08-0.11wt.% Zr, balance Cu) has been performed in the temperature range of 673 K – 773 K and time from 30 min to 5 h to find the peak ageing conditions for this alloy. The peak ageing conditions were achieved at 3 h of heat-treatment at 723 K. An attempt has been made to identify the precipitates using analytical transmission electron microscopy and to classify them based on morphology, sizes and distribution. Besides the larger precipitates of Cu5CrZr, two clearly distinct sizes of smaller precipitates were observed. Electron microscopy revealed that the larger precipitates are having spherical and cuboidal morphology. The temperature dependent flow behavior of Cu-Cr-Zr alloy in peak aged condition was evaluated in the range of 298 K to 1073 K in 100 K interval. The dislocation arrangement and the dislocation precipitate interaction were examined to understand the contribution of the precipitates in strengthening and also in work hardening behavior of the alloy.
Joining of high strength materials using friction stir welding (FSW) is difficult due to severe tool wear and change in the shape/size of the tool. However, quantitative understanding of tool wear ...during FSW of high melting point metallic materials is very limited. Here we present quantitative wear analysis of H13 steel tool during FSW of CuCrZr alloy. Higher amount of total tool wear is observed for faster tool rotational speeds, and slower traverse speeds. Progressive wear rate shows similar relationship with these process parameters during initial traverse stage. With further tool traverse the wear rate decreases significantly and is not much affected by the process parameters. The quantitative wear study provides insights about tool wear during FSW process and would be useful to better estimate and improve tool life. This would also be helpful to optimize the process parameters and tool shape to reduce tool wear during FSW of high strength materials.
•Higher tool RPM leads to greater tool wear due to enhanced surface velocities.•Tool wear decreases with increase in traverse speed due to reduced interaction time.•Progressive wear rate is highest during first 300mm of tool traverse.•Wear rate decreases as tool approaches a self-optimized shape after long traverse.•Effect of process parameters on wear rate is significant only during initial stage.
Previous efforts to report estimates of cancer incidence and mortality in India and its different parts include the National Cancer Registry Programme Reports, Sample Registration System cause of ...death findings, Cancer Incidence in Five Continents Series, and GLOBOCAN. We present a comprehensive picture of the patterns and time trends of the burden of total cancer and specific cancer types in each state of India estimated as part of the Global Burden of Diseases, Injuries, and Risk Factors Study (GBD) 2016 because such a systematic compilation is not readily available.
We used all accessible data from multiple sources, including 42 population-based cancer registries and the nationwide Sample Registration System of India, to estimate the incidence of 28 types of cancer in every state of India from 1990 to 2016 and the deaths and disability-adjusted life-years (DALYs) caused by them, as part of GBD 2016. We present incidence, DALYs, and death rates for all cancers together, and the trends of all types of cancers, highlighting the heterogeneity in the burden of specific types of cancers across the states of India. We also present the contribution of major risk factors to cancer DALYs in India.
8·3% (95% uncertainty interval UI 7·9–8·6) of the total deaths and 5·0% (4·6–5·5) of the total DALYs in India in 2016 were due to cancer, which was double the contribution of cancer in 1990. However, the age-standardised incidence rate of cancer did not change substantially during this period. The age-standardised cancer DALY rate had a 2·6 times variation across the states of India in 2016. The ten cancers responsible for the highest proportion of cancer DALYs in India in 2016 were stomach (9·0% of the total cancer DALYs), breast (8·2%), lung (7·5%), lip and oral cavity (7·2%), pharynx other than nasopharynx (6·8%), colon and rectum (5·8%), leukaemia (5·2%), cervical (5·2%), oesophageal (4·3%), and brain and nervous system (3·5%) cancer. Among these cancers, the age-standardised incidence rate of breast cancer increased significantly by 40·7% (95% UI 7·0–85·6) from 1990 to 2016, whereas it decreased for stomach (39·7%; 34·3–44·0), lip and oral cavity (6·4%; 0·4–18·6), cervical (39·7%; 26·5–57·3), and oesophageal cancer (31·2%; 27·9–34·9), and leukaemia (16·1%; 4·3–24·2). We found substantial inter-state heterogeneity in the age-standardised incidence rate of the different types of cancers in 2016, with a 3·3 times to 11·6 times variation for the four most frequent cancers (lip and oral, breast, lung, and stomach). Tobacco use was the leading risk factor for cancers in India to which the highest proportion (10·9%) of cancer DALYs could be attributed in 2016.
The substantial heterogeneity in the state-level incidence rate and health loss trends of the different types of cancer in India over this 26-year period should be taken into account to strengthen infrastructure and human resources for cancer prevention and control at both the national and state levels. These efforts should focus on the ten cancers contributing the highest DALYs in India, including cancers of the stomach, lung, pharynx other than nasopharynx, colon and rectum, leukaemia, oesophageal, and brain and nervous system, in addition to breast, lip and oral cavity, and cervical cancer, which are currently the focus of screening and early detection programmes.
Bill & Melinda Gates Foundation; and Indian Council of Medical Research, Department of Health Research, Ministry of Health and Family Welfare, Government of India.
► Embrittlement of 304L and 316L welds after aging up to 20,000h. ► Spinodal decomposition and G-phase precipitation in ferrite at 400°C. Only spinodal decomposition at 335 and 365°C. ► Charpy ...impact, microhardness and tensile tests for evaluation of aging embrittlement and its kinetics determined.
Austenitic stainless steel welds in components used in light water reactors are susceptible to thermal aging embrittlement at reactor operating temperature of around 300°C after a long service life. In this study, low temperature aging embrittlement of types 304L and 316L stainless steel welds with 10% ferrite was investigated on the basis of changes in mechanical properties and microstructure after aging up to 20,000h at 335, 365 and 400°C. Spinodal decomposition and G-phase precipitation in the ferrite was observed after aging which lead to embrittlement in the material. In contrast to the small effect on tensile properties, the impact toughness was significantly degraded after aging. Charpy impact test of the aged samples showed decrease in upper-shelf and lower-shelf energy and increase in ductile brittle transition temperature. Large increase in the microhardness of ferrite phase was observed with no change in austenite hardness. The embrittlement in 316L weld was higher compared to 304L weld for similar aging condition. The kinetics of aging embrittlement was established based on Arrhenius relationship. A constant activation energy was determined for 304L weld in the temperature range 335–400°C, however, 316L weld showed different activation energy values in each temperature range.
► Embrittlement study of austenitic stainless steel welds after ageing up to 20,000
h. ► Spinodal decomposition and G-phase precipitation in ferrite at 400
°C. ► Spinodal decomposition of ferrite at ...335 and 365
°C. ► Large decrease in corrosion resistance due to G-phase precipitation. ► Good correlation between electrochemical properties and the degree of embrittlement.
The low temperature thermal ageing embrittlement of austenitic stainless steel welds is investigated after ageing up to 20,000
h at 335, 365 and 400
°C. Spinodal decomposition and G-phase precipitation after thermal ageing were identified by transmission electron microscopy. Ageing led to increase in hardness of the ferrite phase while there was no change in the hardness of austenite. The degree of embrittlement was evaluated by non-destructive methods, e.g., double-loop and single-loop electrochemical potentiokinetic reactivation tests. A good correlation was obtained between the electrochemical properties and hardening of the ferrite phase of the aged materials.
Zr-1Nb alloy is normally processed in two phase region to get desirable microstructure and properties for fuel cladding tube application in the nuclear reactor. Thus, it is important to know the ...deformation behavior of individual phases in the two phase region. However, the conventional approach to develop processing maps is to use flow stress data obtained from hot compression experiments, without accounting for the phases present at different temperatures. This approach fails to bring out the details about the operating deformation mechanism in the individual phases. In order to bring out these details, two new approaches are proposed for developing processing maps. The validity of the approaches is confirmed by performing microstructural analysis using electron backscattered diffraction (EBSD) studies. EBSD analysis of the microstructures obtained after deformation in the two phase region confirmed that α−phase had undergone dynamic recrystallization (DRX) whereas, β−phase exhibited coarse elongated grains. Processing maps developed using the new approaches were able to predict domains of high dissipation efficiency, which is corroborated by microstructural analysis. Also, one of the novel approaches proposed in this work could delineate the contribution of each phase in the two phase region.
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•New processing map developed by incorporating phase information in two phase region.•Dominant phase in two phase region is identified in processing map.•Microstructural analysis confirmed the predictions of the new processing maps.•α-phase undergoes DRX whereas β-phase experiences DRV.
Dynamic materials model (DMM), modified dynamic materials model (MDMM) and α-parameter were used to develop processing maps of Zr-2.5Nb alloy. Gleeble-3800® thermo-mechanical simulator was used to ...obtain flow stress at different temperatures and strain rates in the range of 700–925 °C and 0.01–10 s−1 respectively. Suitability of the three models in predicting the hot deformation behavior of Zr-2.5Nb alloy was evaluated by microstructural studies. DMM was found appropriate to delineate different deformation conditions for this alloy.
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•Flow stress behaviors are discussed during thermo-mechanical processing.•Flow stress in (α+β) phase exhibits softening whereas in β phase it remains almost constant.•We made comparative study using different materials model to delineate the safe and unsafe hot deformation parameters.•Prediction of each model is validated using microstructural study and summarized in a table.•DMM is best predictable model and hot deformation of Zr-2.5Nb alloy is safe at strain rate lower than 1 s−1.
Friction stir welding (FSW) of high melting point metallic (HMPM) materials has limited application due to tool wear and relatively short tool life. Tool wear changes the profile of the tool pin and ...adversely affects weld properties. A quantitative understanding of tool wear and tool pin profile is crucial to develop the process for joining of HMPM materials. Here we present a quantitative wear study of H13 steel tool pin profile for FSW of CuCrZr alloy. The tool pin profile is analyzed at multiple traverse distances for welding with various tool rotational and traverse speeds. The results indicate that measured wear depth is small near the pin root and significantly increases towards the tip. Near the pin tip, wear depth increases with increase in tool rotational speed. However, change in wear depth near the pin root is minimal. Wear depth also increases with decrease in tool traverse speeds. Tool pin wear from the bottom results in pin length reduction, which is greater for higher tool rotational speeds, and longer traverse distances. The pin profile changes due to wear and result in root defect for long traverse distance. This quantitative understanding of tool wear would be helpful to estimate tool wear, optimize process parameters, and tool pin shape during FSW of HMPM materials.
•This Ab-initio study determines lowest enthalpy barrier TP for α→ω in Zr.•Most favorable TP has a C2/c common sp. gr. and 22meV/atom enthalpy barrier at 0K.•This TP comprises of small strains and ...atomic shuffles compared to other TP.•Softening of C44 and ωE2g associated with change in E2g phonon mode potential landscape.•E2g phonon mode and pressure shows a similar topological change in band structure.
This first principles study attempts to find the lowest enthalpy barrier transformation pathway (TP) for pressure induced α→ω transformation in pure Zr by systematically studying TPs suggested experimentally along with TPs generated from symmetry analysis. We find that symmetry generated pathways and model pathways given from experimental inputs essentially outline the same subset of possible pathways. The most favorable TP, comprising of smaller strains and atomic shuffles compared to others, has a C2/c as a common space group along the TP with enthalpy barrier of 22meV/atom at 0K. It is evident from the study that the softening of shear elastic constant C44 and Γ point transverse optical phonon frequency as a function of pressure in α-Zr are associated with change in effective potential landscape for the E2g phonon at Γ point of the Brillouin zone. The calculated electronic band structure as a function of pressure and E2g phonon mode shows a similar topological change in the band structure which drives this transformation.
The sequence of austenite reversion during overageing in 18 Ni (350) maraging steel was examined and its effects on the mechanical properties were evaluated. Austenite with different morphological ...features were identified at different stages of overageing. The reverted austenite caused decrease in the yield strength (YS) and ultimate tensile strength (UTS) and increase in the tensile ductility. Though the presence of austenite appeared to be beneficial to impact toughness in the initial stages of overageing, severe embrittlement was noticed in samples subjected to prolonged ageing. The observed deterioration in toughness with continued overageing was associated with the coarsening of intermetallic precipitates formed during the early stages of ageing. Electron probe micro analysis (EPMA) carried out on fracture surface identified the embrittling species as precipitates rich in titanium and nickel.
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