Dear Colleagues,

Although there has been a recent issue (Metals 2019) devoted to the segregation of atoms to the boundaries, it is believed that this is an area which has tremendous potential for improving the properties of metals and alloys and accounts for the plethora of papers that are being published on the subject and so needs continuous attention. It is believed that the segregation of solute atoms to the grain boundaries and other structural defects as well as the interaction between them can dictate the properties of metals such as strength, ductility and impact behaviour, corrosion and weldability, particularly for steels. There is also a movement to use segregation to the boundaries as a means of designing alloys. This Special Issue is designed to attract more of such papers. Part of this increased interest in the subject has come through the development of new techniques which has enabled accurate studies to be made of the grain boundaries and their contents. There are now many techniques available to identify the atoms at the boundaries (e.g., atom-probe tomography (APT), auger electron spectroscopy (AES) and high-resolution analytical transmission electron microscopy (HRTEM), secondary ion mass spectrometry (SIMs), dual electron energy loss spectroscopy (Dual EELS) as well as the development of theoretical models based on phase-field or molecular dynamics simulations so that grain boundary engineering is becoming a real possibility in alloy design, and papers covering this topic will be welcome.

The Special Issue will cover the following:

• Papers which use modern characterization techniques to identify the atoms at the boundaries and the properties that they are influencing.
• Experimental techniques which can assess segregation, i.e., identification and quantification of the amount of segregation, taking into account factors like cooling rates, temperature and time at temperature and the matrix concentration.
• Competitiveness of elements in reaching the grain boundaries and their choice between segregation to particles in the matrix rather than to the boundaries.
• The role of ionic bonding in controlling the cohesive strength of the boundary.
• The role of dislocations, precipitation and vacant sites at the boundaries in influencing the metallic bonding at the boundaries, as well as experiment-based explanations on clarifying non-equilibrium solute drag effect of solute atoms.
• Presentation of theories to explain why certain atoms which segregate to the grain boundaries in metals influence the bonding, either by strengthening or weakening of the grain boundaries.
• Instances where segregation to the boundaries may influence properties not solely by the bonding but also by other means such as the nucleation sites for the austenite to ferrite transformation in low C steels which boron has been credited as doing.
• Most importantly, papers are required which show how grain boundary segregation can be used as a means of designing alloys to give better properties.

Prof. Dr. Barrie Mintz
Guest Editor

Prof. Dr. Antonio Enrique Salas Reyes
Guest Editor Assistant

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• grain boundary segregation
• ductility
• corrosion
• weldability
• steel
• atom-probe tomography
• auger electron spectroscopy