Mariano Marcos Bárcena

The Influence of the Surface Distribution of Al6(MnFe) Intermetallic on the Electrochemical Response of AA5083 Aluminium Alloy in NaCl Solutions

In this paper the behaviour against pitting corrosion of different samples of AA5083 aluminium alloy has been studied. A correlation between the microstructure of the samples and their susceptibility to pitting has been established. Metallographic analysis combined with SEM and EDS techniques have allowed us to detect three intermetallic compounds in the samples. The particle size distribution and surface density of each intermetallic phase have been evaluated for the three AA5083 alloy samples coming from different suppliers. Significant differences in the microstructure of the three samples have been found. Full immersion test carried out in 3.5% aerated aqueous solutions showed that pitting starts at the locations of the Al 6 (MnFe) intermetallic particles. As a consequence of this, the samples with higher Al 6 (MnFe) content showed a higher pit density on its surface. The results of cyclic polarisation tests showed also a good correlation with the microstructural parameters.

Sliding Wear Behavior of UNS R56400 Titanium Alloy Samples Thermally Oxidized by Laser

Wear of elements subjected to friction and sliding is among the main causes of low tribological performance and short lifetime of strategic materials such as titanium alloys. These types of alloys are widely used in different areas such as aerospace and the biomechanics industry. In this sense, surface modification treatments allow for the overcoming of limitations and improvement of features and properties. In the case of titanium alloys, improvements in the main weaknesses of these materials can be obtained. Laser texturing of UNS R56400 (Ti6Al4V) alloy, according to Unified Numbering System designation, surface layers in a non-protective atmosphere produces an increase of the oxides, especially of titanium dioxide (TiO2) species. The presence of oxides in the alloy results in color tonality variations as well as hardness increases. In addition, specific roughness topographies may be produced by the track of laser beam irradiation. In this research, thermochemical oxidation of UNS R56400 alloy has been developed through laser texturing, using scan speed of the beam (Vs) as the process control variable, and its influence on the sliding wear behavior was analyzed. For this purpose, using pin on disc tribological tests, wear was evaluated from the friction coefficient, and wear mechanisms involved in the process were analyzed. Combined studies of wear mechanisms and the friction coefficient verified that by means of specific surface treatments, an increase in the wear resistance of this type of alloys is generated. The most advantageous results for the improvement of tribological behavior have been detected in textured surfaces using a Vs of 150 mm/s, resulting in a decrease in the friction coefficient values by approximately 20%.Wear of elements subjected to friction and sliding is among the main causes of low tribological performance and short lifetime of strategic materials such as titanium alloys. These types of alloys are widely used in different areas such as aerospace and the biomechanics industry. In this sense, surface modification treatments allow for the overcoming of limitations and improvement of features and properties. In the case of titanium alloys, improvements in the main weaknesses of these materials can be obtained. Laser texturing of UNS R56400 (Ti6Al4V) alloy, according to Unified Numbering System designation, surface layers in a non-protective atmosphere produces an increase of the oxides, especially of titanium dioxide (TiO₂) species. The presence of oxides in the alloy results in color tonality variations as well as hardness increases. In addition, specific roughness topographies may be produced by the track of laser beam irradiation. In this research, thermochemical oxidation of UNS R56400 alloy has been developed through laser texturing, using scan speed of the beam (Vs) as the process control variable, and its influence on the sliding wear behavior was analyzed. For this purpose, using pin on disc tribological tests, wear was evaluated from the friction coefficient, and wear mechanisms involved in the process were analyzed. Combined studies of wear mechanisms and the friction coefficient verified that by means of specific surface treatments, an increase in the wear resistance of this type of alloys is generated. The most advantageous results for the improvement of tribological behavior have been detected in textured surfaces using a Vs of 150 mm/s, resulting in a decrease in the friction coefficient values by approximately 20%.

Sustainable Manufacturing in Aerospace Industry – Analysis of the Viability of Intermediate Stages Elimination in Sheet Processing

Manufacturing performance improvement must take into account energetic, environmental and economic considerations. Thus, when intermediate manufacturing processes are avoided, that performance is improved from the cited viewpoints. In the aeronautical industry, pre-shaped elements of UNS A92024 alloy based structural elements are machined in T3 temper state previously to be thermally treated to reach an O state in order to facilitate its posterior plastic forming process. In this work, a comparative study on the dry turning of UNS A92024 alloy in both states has been achieved in order to analyze the possibilities of eliminating the thermal treatment process, so improving the three above commented considerations. This study has been carried out on the basis of the analysis of surface finish and cutting tool wear.

Microstructural Differences of Adhered Material in the Tool Edge and Tool Rake Face. Application to the Machining of Al Alloys

Tool adhesion wear can be produced by two different ways. On the one hand, direct adhesion wear is caused by the incorporation of tool particles to the chips. On the other hand, indirect adhesion wear is caused by the incorporation of fragment of the workpiece material to the tool. When these fragments are removed, they can drag out tool particles causing tool wear. Indirect adhesion can be localised in the tool edge, giving rise to Built-Up Edge (BUE), or in the tool rake face, giving rise to Built-Up Layer (BUL). In this work microstructural differences between both effects in different machining processes of Al-Cu alloys have been analysed. From these microstructural differences, a model has been proposed for the mechanism of formation of both effects.

A Comparison of BPMN 2.0 with other Notations for Manufacturing Processes

In order to study their current practices and improve on them, manufacturing firms need to view their processes from several viewpoints at various abstraction levels. Several notations have been developed for this purpose, such as Value Stream Mappings or IDEF models. Recently, the BPMN 2.0 standard from the Object Management Group has been proposed for modeling business processes. A process organizes several activities into a single higher-level entity, which can be reused elsewhere in the organization. Its potential for standardizing business interactions is well-known, but there is little work on using BPMN 2.0 to model manufacturing processes. In this work some of the previous notations are outlined and BPMN 2.0 is positioned among them after discussing it in more depth. Some guidelines on using BPMN 2.0 for manufacturing are offered, and its advantages and disadvantages in comparison with the other notations are presented.

Identification, Analysis and Evolution of the Mechanisms of Wear for Secondary Adhesion for Dry Turning Processes of Al-Cu Alloys

In this work, Stereoscopic Optical Microscopy (SOM), Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS) have been applied for analyzing the evolution of tool wear during the dry turning process of aerospace Al-Cu alloys. The results derived from this analysis have revealed that secondary adhesion is the main tool wear mechanism that takes place in such process. So, in the first instants of the machining process, a Built-Up Layer (BUL) is developed onto the tool rake face by thermomechanical causes, promoting the conditions for developing a Built-Up Edge (BUE) which grows to a critical size. Starting from it, BUE is extruded giving rise to secondary BUL-BUE effects. When these are removed, tool particles are dragged out provoking the tool wear.

Tribological Wear Analysis of Laser Surface Treated Ti6Al4V Based on Volume Lost Evaluation

Surface modification of materials through thermal or chemical treatments and coatings development can be used to obtain improved behavior under abrasive and adhesive wear. A great variety of surface structures with different properties can be adapted to the most demanding requirements. This is due to the high number of parameters that can be controlled in each treatment, such as the technique used, the atmosphere, the use of additive elements to the base material, the thickness of the modified layers, etc., In order to monitoring more accurately the wear conditions on the alloy, tribological tests were carried out that enable to control anytime the application parameters of a process, thus generating very accurate, reliable and easier to evaluate data, than industrial machining processes. One of the most significant wear variables in the study is the change in volume of material experienced by the sample after the sliding process. This contribution aims at assessing the volume of worn material, analyzing the tribological behavior of surface treated by laser Ti6Al4V samples.

SOM-SEM-EDS Identification of Tool Wear Mechanisms in the Dry-Machining of Aerospace Titanium Alloys

Titanium based alloys, mainly UNS R56400 (Ti6Al4V), are increasingly being applied in the airship building industry due to its excellent physicochemical properties. Machining operations are usually required in the manufacturing processes of Ti based aerospace structural elements. However, high reactivity of Ti provokes a quick tool wear. So, in order to reach an economically acceptable production level, it is necessary to minimize the costs associated to tool wear. In this work, Scanning Electron Microscopy (SEM), Stereoscopic Optical Microscopy (SOM) and Energy Dispersive Spectroscopy (EDS) have been used for both analysing and identifying secondary adhesion mechanisms that are taking place when an aeronautical titanium alloy is machined. Special severe cutting conditions have been applied. Thus, titanium alloy have been dry machined with TiN coated WC-Co tools. Results obtained have shown that tool wear is controlled by a secondary adhesion mechanism, which presents two stages. A first stage is constituted by a TiOx multi-film formed onto the tool surfaces. A second step involves the mechanical adhesion of the alloy material to those surfaces. When this material is removed, tool particles are dragged off causing tool wear.

Influence of the Dry Turning Parameters on the Ultimate Tensile Strength (UTS) of UNS A92024 Samples

The influence of the forming process in the response into service of the manufactured workpieces, in the first instance, through the surface integrity can be evaluated. The concept of surface integrity includes the assessment of geometrical aspects like shape and dimensions, and physicochemical properties like hardness and corrosion resistance. This work reports on the results of a study of the influence of the turning parameters on the Ultimate Tensile Strength (UTS) of turned bars of UNS A92024 Aluminium-Copper alloy.

Cutting Speed-Feed Based Parametric Model for Macro-Geometrical Deviations in the Dry Turning of UNS A92024 Al-Cu Alloys

This work reports on the results of a study of different macro-geometrical deviation parameters, such as Straightness (SD), Parallelism (PD) and Circularity (CD) as a function of cutting speed (v) and feed (f) of dry turned UNS A92024 (Al-Cu) cylindrical bars. The results obtained have allowed establishing exponentials parametric model for predicting these deviations as a function of those cutting parameters. As a consequence of that, geometrical surfaces SD(f,v), PD(f,v) and CD(f,v) have been developed for this alloy. These surfaces allows determining marginal curves for specific v and f values, respectively, out the parameter ranges employed. So, macro-geometrical deviations can be predicted through this model for v and f values out of those considered in the study for each alloys.