Liquid zinc embrittlement of a high-manganese-content TWIP steel

The cracking resistance of a twinning induced plasticity (TWIP) steel with high-manganese content has been studied in relation to the liquid metal embrittlement phenomenon. This phenomenon was investigated by hot tensile tests carried out on electrogalvanised specimens using a Gleeble® simulator at temperatures ranging from 600°C to 1000°C. The results show that this steel can be embrittled by liquid zinc within a limited range of temperature depending on strain rate.     

Comparative study of local structure in Zr70Al10Ni20 and quasi-crystal-forming Zr70Al9Ni20Pd1 metallic glasses

The local structure of Zr₇₀Al₉Ni₂₀Pd₁ metallic glass, in which a nano-icosahedral quasi-crystalline phase (I-phase) is formed in the primary stage of crystallization, has been examined and compared with that of Zr₇₀Al₁₀Ni₂₀, the supercooled liquid state of which has a high stability. Since the local environments around the Zr and Ni atoms do not change drastically by the addition of 1 at.% Pd to Zr₇₀Al₁₀Ni₂₀, as evidenced by radial distribution function (RDF) and extended x-ray absorption fine structure (EXAFS) studies, we deduce that the icosahedral phase formed in the Zr₇₀Al₉Ni₂₀Pd₁ metallic glass has a local structure similar to that in Zr₇₀Al₁₀Ni₂₀. Although a very slight rearrangement of Zr–Zr atomic pairs occurs during quasi-crystallization, the I-phase formation is achieved without disturbing the dominant local structure in the glassy state of the Zr₇₀Al₉Ni₂₀Pd₁. An icosahedral local structure is proposed for Zr–Al–Ni metallic glass system as well as for primary quasi-crystal (QC)-forming Zr-based metallic glasses.     

Group‐analytic network process for balancing stakeholder views on fire protection of steel‐framed buildings

To select appropriate fire protection options for buildings during their design stage, economic, safety, environmental, and societal criteria need to be accounted for. The divergent and sometimes conflictual desires from different fire design stakeholders involved in the process present a multicriteria decision problem. Design decision criteria and fire protection options can be interdependent, and so there is a need to manage these desires with an advanced decision analysis technique, thereby reducing uncertainties in the complex decision‐making process. The aim of this paper is to use the weighted/geometric mean method‐analytic network process (W/GMM‐ANP) to balance the opinions of fire design stakeholders extracted from 42 structured stakeholder interviews on selecting the most suitable fire protection option for buildings constructed of steel frames. Different categories of interdependent decision elements were developed from 22 design decision criteria and 5 proposed fire protection options to produce a network of decision clusters for multicriteria decision analysis. In the synthesis and ranking of fire protection options, the W/GMM‐ANP accounted for the multiple interdependencies of weighted and unweighted stakeholder desires and managed the complexity of the decision‐making problem. The technique is proposed for approaching suitable group decisions in structural fire design of steel‐framed buildings as well as other performance‐based engineering decision making that may involve multidisciplinary stakeholders.     

Electron spin resonance of hydrogenated amorphous silicon-carbon alloy films prepared by magnetron sputtering

Abstract

New electron spin resonance (ESR) lines with g¹ = 2·0017 and g₂ and g₃ = 2·0006 have been found in the ESR spectra of as-deposited a-Si_1–x C_x:H films prepared by magnetron sputtering of silicon in the gas mixtures of methane and argon. Similarities between the observed spectra and those for the E′ centre in glassy SiO₂ are discussed.     

Attainment of an exceptionally high strength in low-carbon steel along with modest ductility through a novel heat treatment route

ABSTRACT

Over the last few decades, the use of steel (the most significant structural engineering material) is facing a significant challenge due to its replacement by other materials (such as composites) possessing higher strength-to-weight ratio/specific strength. This necessitates further enhancement in the strength of steel. In particular, low-carbon steel, in the annealed condition, suffers from inherent problems of poor strength and discontinuous yielding. In this research work a novel heat treatment route of incomplete austenitisation-based cyclic ice-brine quenching has been adopted on low-carbon steel (AISI 1010 steel containing 0.1 wt.% C) without considering any costly alloying or thermo-mechanical treatment. Accordingly, exceptionally high strength (UTS?=?1.7?GPa) and specific strength (226?MPa?g^?1cm³) are achieved after three cycles along with a modest ductility (% Elongation?=?9). This is the highest strength reported so far for low-carbon steel containing 0.1 wt.% C. Yield point phenomenon is also eliminated. This is attributed to a novel microstructure consisting of highly sub-structured fine plate martensite crystals containing internal twin and dislocation tangles along with dispersion of nano-sized cementite particles and clusters of cementite particles.     

Post-irradiation annealing behaviour of oxide dispersion strengthened Fe-Cr alloys studied by nanoindentation

ABSTRACT

To study the nature of irradiation-induced nanofeatures in oxide dispersion strengthened (ODS) Fe-Cr alloys, post-irradiation isochronal thermal annealing up to 600°C was performed for ODS Fe-9%Cr and Fe-14%Cr alloys ion-irradiated at 300°C and 500°C. Nanoindentation indicated hardening for all as-irradiated alloys and complete hardness recovery upon post-irradiation annealing. Cross-sectional TEM indicated an irradiation-induced defect band near peak damage mainly consisting of dislocation loops. Candidate mechanisms of recovery were critically evaluated. Shrinkage of loops via capture of thermal vacancies was found to correctly reflect the annealing behaviour of ODS Fe-9Cr irradiated at 300°C.     

Importance of crack-propagation-induced ε-martensite in strain-controlled low-cycle fatigue of high-Mn austenitic steel

We investigated the roles of deformation-induced ε-martensitic transformation on strain-controlled low-cycle fatigue (LCF) through crack-propagation analysis involving a notching technique that used a focused ion beam (FIB) setup on Fe–30Mn–4Si–2Al austenitic steel. Using the FIB notch, we separated the microstructure evolution into macroscopic cyclic deformation-induced and crack-propagation-induced microstructures. Following this, we clarified the fatigue crack-propagation-induced ε-martensitic transformation to decelerate crack propagation at a total strain range of 2%, obtaining an extraordinary LCF life of 1.1 × 10⁴ cycles.     

Mantle region accommodating two-dimensional grain boundary sliding in ODS ferritic steel

Two-dimensional grain-boundary sliding (GBS) was achieved microscopically in an oxide-dispersion-strengthened ferritic steel with an elongated and aligned grain structure, which was deformed perpendicular to the long axis. At the border between superplastic regions II and III, microscopic deformation was observed using sub-micron grids drawn on the material surface using a focused ion beam. GBS was accommodated by intragranular deformations in narrow areas around grain boundaries, which has been predicted by earlier researchers as characteristics of the core–mantle model. These observations suggest that dislocations slip only in the mantle regions around wavy boundaries to relax the stress concentration caused by GBS during superplasticity.     

On the AlN precipitation and grain refinement in the Al(N)-added medium C–Mn steels

The precipitation of AlN particles and grain refinement in the Al(N)-added medium C–Mn steel have been studied using a Gleeble hot-deformation simulator and extraction replica TEM technique. No significant grain refinement occurs during either hot-rolling or hot-deformation/isothermal-holding, which is due to the absence of AlN precipitation; the lack of precipitation is caused by an unusually high-energy barrier for nucleation. Abrupt grain refinement occurs on reheating because of the copious precipitation of AlN during reheating. The copious precipitation of AlN during reheating is possible because thermally unstable Fe-rich sulphides act as precursors for AlN precipitation during reheating.     

Nanoscale partitioning of Mn between austenite and martensite revealed by Curie temperature variations

The partitioning of Mn between deformation-induced martensite and austenite phases of a Fe?18Mn?2Al?2Si?0.04C high-Mn steel was studied by tracking variations in the Curie temperature of martensite after exposure to successively higher annealing temperatures. The increase in Curie temperature was justified by the Mn depletion of martensite. Assuming a linear relationship between the Curie temperature and Mn concentration, the average Mn concentration of martensite was expressed as a function of annealing temperature. The proposed method, which is applicable in a dilatometer with inductive heating, enables the ready estimation of Mn partitioning in intercritically annealed medium- and high-Mn steels.