Observation of Precipitation Evolution in Fe-Ni-Mn-Ti-Al Maraging Steel by Atom Probe Tomography

We describe the full decomposition sequence in an Fe-Ni-Mn-Ti-Al maraging steel during isothermal annealing at 550 °C. Following significant pre-precipitation clustering reactions within the supersaturated martensitic solid solution, (Ni,Fe)3Ti and (Ni,Fe)3(Al,Mn) precipitates eventually form after isothermal aging for ~60 seconds. The morphology of the (Ni,Fe)3Ti particles changes gradually during aging from predominantly plate-like to rod-like, and, importantly, Mn and Al were observed to segregate to these precipitate/matrix interfaces. The (Ni,Fe)3(Al,Mn) precipitates occurred at two main locations: uniformly within the matrix and at the periphery of the (Ni,Fe)3Ti particles. We relate this latter mode of precipitation to the Mn-Al segregation

Elevated risk of infection with SARS-CoV-2 Beta, Gamma, and Delta variants compared with Alpha variant in vaccinated individuals

The extent to which severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants of concern (VOCs) break through infection- or vaccine-induced immunity is not well understood. We analyzed 28,578 sequenced SARS-CoV-2 samples from individuals with known immune status obtained through national community testing in the Netherlands from March to August 2021. We found evidence of an increased risk of infection by the Beta (B.1.351), Gamma (P.1), or Delta (B.1.617.2) variants compared with the Alpha (B.1.1.7) variant after vaccination. No clear differences were found between vaccines. However, the effect was larger in the first 14 to 59 days after complete vaccination compared with ≥60 days. In contrast to vaccine-induced immunity, there was no increased risk for reinfection with Beta, Gamma, or Delta variants relative to the Alpha variant in individuals with infection-induced immunity.</p

Observation of Precipitation Evolution in Fe-Ni-Mn-Ti-Al Maraging Steel by Atom Probe Tomography

We describe the full decomposition sequence in an Fe-Ni-Mn-Ti-Al maraging steel during isothermal annealing at 550 °C. Following significant pre-precipitation clustering reactions within the supersaturated martensitic solid solution, (Ni,Fe)3Ti and (Ni,Fe)3(Al,Mn) precipitates eventually form after isothermal aging for ~60 seconds. The morphology of the (Ni,Fe)3Ti particles changes gradually during aging from predominantly plate-like to rod-like, and, importantly, Mn and Al were observed to segregate to these precipitate/matrix interfaces. The (Ni,Fe)3(Al,Mn) precipitates occurred at two main locations: uniformly within the matrix and at the periphery of the (Ni,Fe)3Ti particles. We relate this latter mode of precipitation to the Mn-Al segregation

Mircostructure and texture of warm rolled extra-low carbon steel alloyed with chromium

Contrary to interstitial free (IF) steel grades, low carbon steels exhibit dynamic strain ageing during warm rolling due to the presence of solute carbon. This leads to the reduced formation of grains containing in-grain shear bands and a weak but desirable {111} recrystallisation texture on annealing, when compared to IF steels. Addition of Cr leads to carbon depletion in the ferrite matrix as a result of Cr carbide formation. The warm rolling schedule could also have an effect on the amount of carbides and grains containing in-grain shear bands formed. In this work extra low carbon steel alloyed with 0.78wt%Cr was subjected to two different warm rolling schedules: (i) rolling to 65% reduction at 913K and (ii) rolling to 80% reduction at 853K. The microstructure was characterised using optical metallography, transmission electron microscopy, energy dispersive X-ray spectroscopy and bulk texture analysis. The results have shown that increase in the severity of deformation resulted in a very slight increase in the number of grains containing in-grain shear bands. The intensity of ND-fibre, which comprises of grains withaxes parallel to the normal direction (ND), was slightly higher in the steel warm rolled at 853K than at 913K. In both steels several types of carbides were formed, such as Cr3C2, Cr23C6 and Cr19Fe4C6. The density of fine strain-induced carbides in the steel after 80% reduction was by order of magnitude higher than after warm rolling to 65% reduction. Based on their size, the carbides could be divided in two distinctive groups: (i) coarse carbides, predominantly located at ferrite grain boundaries and microband boundaries; and (ii) fine carbides, relatively uniformly distributed within the microbands