EUROMAT 2019 Symposia on Processing

This issue of JMEP contains invited, peer-reviewed papers presented at the European Congress and Exhibition on Advanced Materials and Processes (EUROMAT 2019), held on September 1–5, 2019, in Stockholm, Sweden, in two symposia from the Area C “Processing”: C6 “Joining,” organized by Anna Zervaki (University of Thessaly, Greece), Ivan Kaban (IFW Dresden, Germany), and C. Sommitsch (Technische Universität Graz, Austria) C8 “Interface Design and Modelling, Wetting, and High-Temperature Capillarity,” organized by Pavel Protsenko (M.V. Lomonosov Moscow State University, Russian Federation), Fabrizio Valenza (CNR—ICMATE, Genoa, Italy), and Simeon Agathopoulos (University of Ioannina, Greece) The research works in the field of joining technologies, presented at the C6 symposium, concerned soldering, brazing, diffusion bonding, resistance spot welding, friction stir welding, and riveting techniques. The symposium C8 covered research topics on grain boundary wetting, surface energy of liquid metals and interfacial phenomena, considering fundamental as well as applied issues related to materials joining, and interface design. We wish to thank the authors for the written contributions and acknowledge the reviewers for their careful reading and evaluation of the manuscripts and valuable suggestions to improve the quality of the papers. We are grateful to the editor-in-chief of JMEP, Dr. Rajiv Asthana, and the ASM journal staff, including Mary Anne Fleming, senior content developer; Kate Doman, content developer (journals); and Vincent Katona, production coordinator; for the opportunity to publish the symposia contributions in this issue and for their professional and friendly support during the entire reviewing and publication process. We hope this collection will stimulate fresh thinking and promote further research on joining and interfacial phenomena

Automated office blood pressure measurements in primary care are misleading in more than one third of treated hypertensives: The VALENTINE-Greece Home Blood Pressure Monitoring study

Abstract Background This study assessed the diagnostic reliability of automated office blood pressure (OBP) measurements in treated hypertensive patients in primary care by evaluating the prevalence of white coat hypertension (WCH) and masked uncontrolled hypertension (MUCH) phenomena. Methods Primary care physicians, nationwide in Greece, assessed consecutive hypertensive patients on stable treatment using OBP (1 visit, triplicate measurements) and home blood pressure (HBP) measurements (7 days, duplicate morning and evening measurements). All measurements were performed using validated automated devices with bluetooth capacity (Omron M7 Intelli-IT). Uncontrolled OBP was defined as ≥140/90 mmHg, and uncontrolled HBP was defined as ≥135/85 mmHg. Results A total of 790 patients recruited by 135 doctors were analyzed (age: 64.5 ± 14.4 years, diabetics: 21.4%, smokers: 20.6%, and average number of antihypertensive drugs: 1.6 ± 0.8). OBP (137.5 ± 9.4/84.3 ± 7.7 mmHg, systolic/diastolic) was higher than HBP (130.6 ± 11.2/79.9 ± 8 mmHg; difference 6.9 ± 11.6/4.4 ± 7.6 mmHg, p Conclusions In primary care, automated OBP measurements are misleading in approximately 40% of treated hypertensive patients. HBP monitoring is mandatory to avoid overtreatment of subjects with WCH phenomenon and prevent undertreatment and subsequent excess cardiovascular disease in MUCH

Simulation of dissolution and coarsening in the HAZ of 6061 Al- alloy during laser welding

Application of laser beam welding (LBW) in heat treatable aluminum alloys causes softening of the heat affected zone (HAZ). This loss in hardness, reflects the relevant microstructural changes due to dissolution and coarsening of the strengthening precipitates during the weld thermal cycle. The main objective of the present work is the simulation of the microstructural evolution in the HAZ of the 6xxx Al alloys, in order to predict the hardness drop as a function of welding conditions. Towards this scope, bead-on-plate laser welding experiments have been conducted. Weld thermal cycles in the HAZ were determined by the finite element method. The volume fraction and average precipitate size, were calculated by employing the methodology of computational thermodynamics and kinetics for several weld thermal cycles. These microstructural characteristics were incorporated in relevant models in order to predict hardness variation. Calculated hardness profiles in the HAZ are in good agreement with the experimental values. Copyright © 2006 ASM International®

Computational kinetics simulation of the dissolution and coarsening in the HAZ during laser welding of 6061-T6 Al-alloy

Laser beam welding (LBW) has become common practice in the production lines of several industrial sectors including the electronics, domestic appliances, and automotive industries. The advantages of LBW over conventional fusion welding processes (mainly GMAW and GTAW) is the lower welding heat input and smaller weld pool and HAZ dimensions, which are associated with lower residual stresses and distortion. In addition to the general problems encountered during the application of LBW on aluminum alloys (high reflectivity, porosity, loss of alloying elements), the most important problem, which concerns the heat treatable alloys, is the softening of the HAZ due to the dissolution and coarsening of the strengthening precipitates. The main objective of the present work is the simulation of the microstructural evolution in the HAZ in order to predict the hardness drop of the HAZ as a function of welding conditions. Models for the numerical simulation of precipitation, dissolution, and coarsening of beta-Mg2Si phase were developed and solved with the use of the computational thermodynamics and kinetics software DICTRA. In this way the volume fraction and average precipitate size were calculated for several types of weld thermal cycles, under extremely nonisothermal conditions. Calculated hardness profiles in the HAZ are in good agreement with the experimental values. The above results point to the conclusion that it is possible to simulate the microstructure evolution and hardness in the HAZ of aluminum laser welds, thus opening the way for a more precise control and design of LBW of aluminum alloys

Inverse Thermal Analysis of Heat-Affected Zone in Al2129 and Al2198 Laser Welds

Case study analyses of A12139 and Al2198 laser welds are presented. These analyses demonstrate the concept of constructing parameter spaces for prediction of properties within the heat-affected zone (HAZ) of welds using inverse modeling, which are in turn for process control. The construction of these parameter spaces consists of two procedures. One procedure entails calculation of a parameterized set of temperature histories by inverse analysis of the heat deposition occurring during welding. The other procedure entails correlating these temperature histories with a specific physical property of the weld that is measurable. The analyses presented here examines some characteristics of inverse modeling with respect to the prediction of hardness within the HAZ for deep penetration laser welding of the Aluminum alloys A12139 and Al2198. This study further demonstrates the feasibility of constructing a parameter space for the prediction of weld properties using weld cross section measurements that are independent of weld process conditions

Corrosion damage evolution of the aircraft aluminum alloy 2024 T3

Purpose - The purpose of this paper is to quantify the corrosion damage evolution that has occurred on the aircraft aluminum alloy 2024 after the exposure to Exfoliation Corrosion Test (EXCO) solution. Moreover, the effect of the evolving corrosion damage on the materials mechanical properties has been assessed. The relevance of the corrosion damage induced by the exposure to the laboratory EXCO for linking it to the damage developed after the exposure of the material on several outdoor corrosive environments or in service is discussed. Design/methodology/approach - To induce corrosion damage the EXCO has been used. For the quantification of corrosion damage the metallographic features considered have been pit depth, diameter, pitting density and pit shape. The effect of the evolving corrosion damage on the materials mechanical properties has been assessed by means of tensile tests on pre corroded specimens. Findings - The results have shown that corrosion damage starts from pitting and evolves to exfoliation, after the development of intergranular corrosion. This evolution is expressed by the increase of the depth of attack, as well as through the significant growth of the diameter of the damaged areas. The results of the tensile tests performed on pre corroded material made an appreciable decrease of the materials tensile properties evident. The decrease of the tensile ductility may become dramatic and increases on severity with increasing corrosion exposure time. SEM fractography revealed a quasi-cleavage zone beneath the depth of corrosion attack. Originality/value - The results underline the impact of corrosion damage on the mechanical behavior of the aluminum alloy 2024 T3 and demonstrate the need for further investigation of the corrosion effect on the structural integrity of the material. This work provides an experimental database concerning the quantification of corrosion damage evolution and the loss of material properties due to corrosion. © Emerald Group Publishing Limited

Rolling contact fatigue of rails

Rolling contact fatigue (RCF) has been of increasing concern in the recent years regarding the safe operation of high-speed railway track with high traffic intensity. The present paper summarizes the results of an on-going investigation of RCF damage encountered in the Athens Metro. The objective of the investigation has been to determine the initiation and propagation of RCF cracks and to determine their geometrical characteristics. A thorough metallographic investigation of track regarding shelling and spalling defects showed the development of a subsurface network of cracks. An analysis of the Hertzian stress field was employed in order to determine the conditions for first yield and shakedown limits as a function of loading conditions

Simulation of the transformation of iron intermetallics during homogenization of 6xxx series extrudable aluminum alloys

A computational simulation of the beta-AlFeSi to alpha-AlFeSi transformation has been performed in this work by integrating the process steps of solidification and homogenization. The composition profiles of alloying elements as well as the profiles of weight fractions of all solid phases computed after solidification were entered as input for the simulation of the homogenization process which involves the dissolution of the Mg2Si and the transformation of beta-AlFeSi to alpha-AlFeSi intermetallics. The transformation fraction was computed as a function of homogenization temperature and time and the transformation kinetics compares well with published experimental data. The evolution of alpha-AlFeSi weight fraction profile and the effect of grain size on transformation kinetics were also computed. (C) 2012 Elsevier B.V. All rights reserved

Analysis of heat affected zone in Al1239 and Al2198 laser welds using inverse modeling

Case study analyses of Al2139 and Al2198 laser welds are presented. These analyses demonstrate the concept of constructing parameter spaces for prediction of properties within the Heat Affected Zone (HAZ) of welds using inverse modeling, which are in turn for process control. The construction of these parameter spaces consists of two procedures. One procedure entails calculation of a parameterized set of temperature histories by inverse analysis of the heat deposition occurring during welding. The other procedure entails correlating these temperature histories with a specific physical property of the weld that is measurable. The analysis presented here examines some characteristics of inverse modeling with respect to the prediction of hardness within the HAZ for deep penetration laser welding of the Aluminum alloys Al2139 and Al2198. This study further demonstrates the feasibility of constructing a parameter space for the prediction of weld properties using weld cross section measurements that are independent of weld process conditions. Copyright © 2013 ASM International® All rights reserved

Fatigue failure investigation of pre-corroded and laser-welded Al-Cu-Mg-Ag Alloy with different temper condition

The fatigue failure mechanisms of pre-corroded, laser beam welded Al-Cu-Mg-Ag alloy in different temper conditions (T3,T8) have been investigated. Aging influences the corrosion behavior of laser welds. In the T3 temper, corrosion attack is in the form of pitting in the weld area, while in the T8 temper corrosion is in the form of intergranular corrosion in the base metal. In the latter case corrosion is attributed to the presence of grain boundary precipitates in the base metal. Corrosion degrades the fatigue behaviour of 2139 welds. The degradation is equal for both the T 3 and T 8 tempers and for the corrosion exposure selected in this study corresponds to a 52% reduction in fatigue limit. In both cases fatigue crack initiation is associated with corrosion pits. In the T3 temper, the fatigue crack initiation site is at the weld metal/HAZ interface, while for the T 8 temper the initiation site is at the base metal. Fatigue crack initiation in uncorroded 2139 welds occurs at the weld toe at the root side, the weld reinforcement playing a principal role as stress concentration site. The fatigue crack propagates through the PMZ and the weld metal in all cases. Fatigue crack initiation in the corroded 2139 welds occurs exclusively at corrosion pits which act as stress raisers