Current Challenges and Opportunities in Microstructure-Related Properties of Advanced High-Strength Steels

This is a viewpoint paper on recent progress in the understanding of the microstructure–property relations of advanced high-strength steels (AHSS). These alloys constitute a class of high-strength, formable steels that are designed mainly as sheet products for the transportation sector. AHSS have often very complex and hierarchical microstructures consisting of ferrite, austenite, bainite, or martensite matrix or of duplex or even multiphase mixtures of these constituents, sometimes enriched with precipitates. This complexity makes it challenging to establish reliable and mechanism-based microstructure–property relationships. A number of excellent studies already exist about the different types of AHSS (such as dual-phase steels, complex phase steels, transformation-induced plasticity steels, twinning-induced plasticity steels, bainitic steels, quenching and partitioning steels, press hardening steels, etc.) and several overviews appeared in which their engineering features related to mechanical properties and forming were discussed. This article reviews recent progress in the understanding of microstructures and alloy design in this field, placing particular attention on the deformation and strain hardening mechanisms of Mn-containing steels that utilize complex dislocation substructures, nanoscale precipitation patterns, deformation-driven transformation, and twinning effects. Recent developments on microalloyed nanoprecipitation hardened and press hardening steels are also reviewed. Besides providing a critical discussion of their microstructures and properties, vital features such as their resistance to hydrogen embrittlement and damage formation are also evaluated. We also present latest progress in advanced characterization and modeling techniques applied to AHSS. Finally, emerging topics such as machine learning, through-process simulation, and additive manufacturing of AHSS are discussed. The aim of this viewpoint is to identify similarities in the deformation and damage mechanisms among these various types of advanced steels and to use these observations for their further development and maturation

Impact of opioid-free analgesia on pain severity and patient satisfaction after discharge from surgery: multispecialty, prospective cohort study in 25 countries

Background: Balancing opioid stewardship and the need for adequate analgesia following discharge after surgery is challenging. This study aimed to compare the outcomes for patients discharged with opioid versus opioid-free analgesia after common surgical procedures.Methods: This international, multicentre, prospective cohort study collected data from patients undergoing common acute and elective general surgical, urological, gynaecological, and orthopaedic procedures. The primary outcomes were patient-reported time in severe pain measured on a numerical analogue scale from 0 to 100% and patient-reported satisfaction with pain relief during the first week following discharge. Data were collected by in-hospital chart review and patient telephone interview 1 week after discharge.Results: The study recruited 4273 patients from 144 centres in 25 countries; 1311 patients (30.7%) were prescribed opioid analgesia at discharge. Patients reported being in severe pain for 10 (i.q.r. 1-30)% of the first week after discharge and rated satisfaction with analgesia as 90 (i.q.r. 80-100) of 100. After adjustment for confounders, opioid analgesia on discharge was independently associated with increased pain severity (risk ratio 1.52, 95% c.i. 1.31 to 1.76; P < 0.001) and re-presentation to healthcare providers owing to side-effects of medication (OR 2.38, 95% c.i. 1.36 to 4.17; P = 0.004), but not with satisfaction with analgesia (beta coefficient 0.92, 95% c.i. -1.52 to 3.36; P = 0.468) compared with opioid-free analgesia. Although opioid prescribing varied greatly between high-income and low- and middle-income countries, patient-reported outcomes did not.Conclusion: Opioid analgesia prescription on surgical discharge is associated with a higher risk of re-presentation owing to side-effects of medication and increased patient-reported pain, but not with changes in patient-reported satisfaction. Opioid-free discharge analgesia should be adopted routinely

Quantifying The Evolution Of Crystal Stresses During Monotonic And Cyclic Loading Using Finite Element Simulations

The focus of the current work is on investigating the orientation dependent micromechanical response of face-centered cubic (fcc) polycrystals using crystal-based elastoplastic finite element simulations. This dissertation contains three related studies examining the evolution of the lattice strains and the crystal stresses in fcc polycrystalline aggregates subjected to monotonic and cyclic loading. These three studies, which can be read independently, are presented in Chapters 1, 2 and 3. Chapter 1 contains an investigation into the evolution of the orientation dependent lattice strain response in fcc polycrystals under monotonic tensile loading, particularly in the elastic-plastic transition regime leading up to fullydeveloped plasticity. The lattice strains, when plotted as a function of the macroscopic stress, begin to deviate from linear behavior in the elastic-plastic transition regime when certain sets of crystals begin yielding before others. It is demonstrated that the progression of yielding in different sets of crystals is influenced by a combination of the single crystal elastic and plastic anisotropies, which can be quantified by the directional strength-to-stiffness ratio [1]. Chapter 2 examines the evolution of the lattice strains and the crystal scale stress distributions in fcc polycrystals under fully-reversed, strain-controlled cyclic loading with respect to the concepts of the directional strength-to-stiffness ratio [1] and the vertices of the single crystal yield surface [2], which have previously only been applied to monotonic tensile loading. These two concepts are derived from the single crystal elastic and plastic anisotropic properties and are used to explain observed behaviors in the lattice strain response such as the size and shape of the lattice strain hysteresis loops. Chapter 3 presents a coordinated approach to quantifying the evolution of lattice strains in an AA7075-T6 aluminum alloy under in situ zero-tension cyclic loading using high-energy synchotron x-ray diffraction experiments and crystal-based finite element simulations. This dissertation involves only the computational aspect of this coordinated approach. Lattice Strain Pole Figures (SPFs) are constructed from both measured and computed lattice strains and comparisons are made at the same macroscopic stress on several cycles in the loading history. Trends in the evolution of crystal quantities such as the crystal stresses, slip system activity and the slip system strengths, which are available from the simulation data, are examined and explained in a consistent manner with respect to the single crystal yield surface topology. The final chapter, Chapter 4, is a brief summary of the preceding chapters highlighting the main contributions of this dissertation

Current challenges and opportunities in microstructure-related properties of advanced high-strength steels

This is a viewpoint paper on recent progress in the understanding of the microstructure–property relations of advanced high-strength steels (AHSS). These alloys constitute a class of high-strength, formable steels that are designed mainly as sheet products for the transportation sector. AHSS have often very complex and hierarchical microstructures consisting of ferrite, austenite, bainite, or martensite matrix or of duplex or even multiphase mixtures of these constituents, sometimes enriched with precipitates. This complexity makes it challenging to establish reliable and mechanism-based microstructure–property relationships. A number of excellent studies already exist about the different types of AHSS (such as dual-phase steels, complex phase steels, transformation-induced plasticity steels, twinning-induced plasticity steels, bainitic steels, quenching and partitioning steels, press hardening steels, etc.) and several overviews appeared in which their engineering features related to mechanical properties and forming were discussed. This article reviews recent progress in the understanding of microstructures and alloy design in this field, placing particular attention on the deformation and strain hardening mechanisms of Mn-containing steels that utilize complex dislocation substructures, nanoscale precipitation patterns, deformation-driven transformation, and twinning effects. Recent developments on microalloyed nanoprecipitation hardened and press hardening steels are also reviewed. Besides providing a critical discussion of their microstructures and properties, vital features such as their resistance to hydrogen embrittlement and damage formation are also evaluated. We also present latest progress in advanced characterization and modeling techniques applied to AHSS. Finally, emerging topics such as machine learning, through-process simulation, and additive manufacturing of AHSS are discussed. The aim of this viewpoint is to identify similarities in the deformation and damage mechanisms among these various types of advanced steels and to use these observations for their further development and maturation.(OLD) MSE-