Nanostructural Engineering of Steel

The concept of microstructural engineering of steels is well established and is the basis for a wide range of processes and products. Recently, though, there has been increasing emphasis in developing microstructures that have submicron length scales and also in understanding in far greater detail the structures and solute effects that are occurring at the nanoscale. In this review it is proposed that we are heading towards the situation where we are applying nanostructural engineering concepts in the development of new steels. A range of examples are given as well as a discussion of the potential impact of new processing routes. Clearly the future advances will be driven through improved characterization methods, such as atom probe tomography, in combination with advanced modeling

A study of the strengthening mechanism in the thermomechanically processed TRIP/TWIP steel

The strengthening mechanism responsible for the unique combination of ultimate tensile strength and elongation in a multiphase Fe-0.2C-1.5Mn-1.2Si-0.3Mo-0.6Al-0.02Nb (wt%) steel was studied. The microstructures with different volume fraction of polygonal fenite, bainite and retained austenite were simulated by controlled thermomechanical processing. The interupted tensile test was used to study the bainitic ferrite, retained austenite and polygonal ferrite behavior as a function of plastic strain. X-ray analysis was used to characterize the volume fraction and carbon content of retained austenite. TEM and heat-tinting were utilized to analyze the effect of bainitic fenite morphology on the strain induced transformation of retained austenite and retained austenite twinning as a function of strain in the bulk material. The study has shown that the austenite twinning mechanism is more preferable than the transformation induced plasticity mechanism during the early stages of deformation for a microstructure containing I5% polygonal ferrite, while the transformation induced plasticity effect is the main mechanism in when there is 50% of polygonal ferrite in the microstructure. The baillitic fenite morphology affects the deformation mode of retained austenite during straining. The polygonal fenite behavior during straining depends on dislocation substructure tonned due to the deformation and the additional mobile dislocations caused by the TRIP effect. TRIP and TWIP effects depend not only on the chemical and mechanical stability of retained austenite, but also on the interaction of the phases during straining.<br /

The effect of multiple deformations on the formation of ultrafine grained steels

A C-Mn-Nb-Ti steel was deformed by hot torsion to study ultrafine ferrite formation through dynamic strain-induced transformation (DSIT) in conjunction with air cooling. A systematic study was carried out first to evaluate the effect of deformation temperature and prior austenite grain size on the critical strain for ultrafine ferrite formation (&epsilon; C,UFF) through single-pass deformation. Then, multiple deformations in the nonrecrystallization region were used to study the effect of thermomechanical parameters (i.e., strain, deformation temperature, etc.) on &epsilon; C,UFF. The multiple deformations in the nonrecrystallization region significantly reduced &epsilon; C,UFF, although the total equivalent strain for a given thermomechanical condition was higher than that required in single-pass deformation. The current study on a Ni-30Fe austenitic model alloy revealed that laminar microband structures were the key intragranular defects in the austenite for nucleation of ferrite during the hot torsion test. The microbands were refined and overall misorientation angle distribution increased with a decrease in the deformation temperature for a given thermomechanical processing condition. For nonisothermal multipass deformation, there was some contribution to the formation of high-angle microband boundaries from strains at higher temperature, although the strains were not completely additive.<br /

Inequalities in higher education in low‐ and middle‐income countries:A scoping review of the literature

Motivation:  Higher  education  is  regarded  as  a  key  instrument  to  enhance  socioeconomic  mobility  andreduce inequalities. Recent literature reviews have examined inequalities in the higher education systemsof  high-income  countries,  but  less  is  known  about  the  situation  in  low-  and  middle-income  countries,where higher education is expanding fast.Purpose:  The  article  reviews  the  academic  literature  on  higher  education  in  low-  and  middle-incomecountries using a research framework inspired by social justice and capability approaches. It considers the financial,  socio-cultural,  human,  and  political  resource  domains  on  which  people  draw,  and  how  they relate to access, participation, and outcomes in higher education.Methods: A literature search for studies explicitly discussing in-country  inequalities  in  higher  education revealed  22  publications. Substantial  knowledge  gaps remain,  especially  regarding  the  political  (and decision-making)  side  of  inequalities;  the  ideologies  and  philosophies  underpinning  higher  education systems; and the linkages between resource domains, both micro and macro.Findings:  The  review  highlights  key  elements  for  policy-makers  and  researchers:  (1)  the  financial  lens alone  is  insufficient  to  understand  and  tackle  inequalities,  since  these  are  also  shaped  by  human  and other non-financial factors; (2) socio-cultural constructs are central in explaining unequal outcomes; and (3) inequalities develop throughout one’s life and need to be considered during, but also before and afterhigher education.  The scope  of  inequalities  is  wide, and  the literature  offers a  few ideas  for short-term fixes such as part-time and online education.Policy implications: Inclusive policy frameworks for higher education should include explicit goals related to (in)equality,  which  are  best  measured in  terms  of  the  extent  to  which  certain  actions  or  choices are feasible for all. Policies in these frameworks, we argue, should go beyond providing financial support, and also address socio-cultural and human resource constraints and challenges in retention, performance, and labour market outcomes. Finally, they should consider relevant contextual determinants of inequalities.</p

Evolution of microstructure and crystallographic texture during dissimilar friction stir welding of duplex stainless steel to low carbon-manganese structural steel

Electron backscattered diffraction (EBSD) was used to analyze the evolution of microstructure and crystallographic texture during friction stir welding of dissimilar type 2205 duplex stainless steel (DSS) to type S275 low carbon-manganese structural steel. The results of microstructural analyses show that the temperature in the center of stirred zone reached temperatures between Ac 1 and Ac 3 during welding, resulting in a minor ferrite-to-austenite phase transformation in the S275 steel, and no changes in the fractions of ferrite and austenite in the DSS. Temperatures in the thermomechanically affected and shoulder-affected zones of both materials, in particular toward the root of the weld, did not exceed the Ac 1 of S275 steel. The shear generated by the friction between the material and the rotating probe occurred in austenitic/ferritic phase field of the S275 and DSS. In the former, the transformed austenite regions of the microstructure were transformed to acicular ferrite, on cooling, while the dual-phase austenitic/ferritic structure of the latter was retained. Studying the development of crystallographic textures with regard to shear flow lines generated by the probe tool showed the dominance of simple shear components across the whole weld in both materials. The ferrite texture in S275 steel was dominated by D 1, D 2, E, E¯ , and F, where the fraction of acicular ferrite formed on cooling showed a negligible deviation from the texture for the ideal shear texture components of bcc metals. The ferrite texture in DSS was dominated by D 1, D 2, I, I¯ , and F, and that of austenite was dominated by the A, A¯ , B, and B¯ of the ideal shear texture components for bcc and fcc metals, respectively. While D 1, D 2, and F components of the ideal shear texture are common between the ferrite in S275 steel and that of dual-phase DSS, the preferential partitioning of strain into the ferrite phase of DSS led to the development of I and I¯ components in DSS, as opposed to E and E¯ in the S275 steel. The formations of fine and ultrafine equiaxed grains were observed in different regions of both materials that are believed to be due to strain-induced continuous dynamic recrystallization (CDRX) in ferrite of both DSS and S275 steel, and discontinuous dynamic recrystallization (DDRX) in austenite phase of DSS

Global Climate Change, Technology Transfer and Trade with Complete Specialization

The paper develops a model in which a country with better technology for abatement of Green House Gas (GHG) emission (the North) commits to an international protocol to keep the global GHG emission within a specified limit while it helps the mitigation effort in the other country (the South) with unconditional transfer of abatement technology. It finds out in the autarkic (no trade) equilibrium the technology transfer offer from the North is always accepted by the South. The North may offer either a partial or a complete technology transfer. If partial technology transfer is offered it finds out the determinants of the extent of technology transfer. Then it compares the autarkic equilibrium with equilibrium where trade with complete specialization occurs and finds out that trade limits the scope of technology transfer as an instrument for mitigation of global GHG emission

Catastrophic antiphospholipid syndrome presenting as fever of unknown origin

Antiphospholipid syndrome is characterized by the presence of antiphospholipid antibodies with characteristic clinical manifestation, which include venous, arterial thrombosis, thrombotic microangiopathy, and recurrent fetal loss. The syndrome can be secondary to many causes including systemic lupus erythematosus (SLE) or "primary" antiphospholipid syndrome (APLS). We report a case of a man with catastrophic antiphospholipid syndrome (CAPS), which occurs when three or more organ systems are affected by thrombosis in less than a week. Catastrophic antiphospholipid syndrome is uncommon but often fatal. The patient received a successful treatment that controlled this disease and included intravenous heparin, antiplatelet, intravenous corticosteroid, and plasmapheresis