Materials Science Forum Vol. 713

Abstract: As it is well-known, TRIP 800 steels modify their structure with the deformation grade. So, part of the retained austenite turns into martensite by plastic deformation. The usual techniques tried out to evaluate this transformation whether do not lead to obtain good results or the experimentation with them is very complex. In this work, a magnetic induction method is experimented and developed in order to determine the evolution of a TRIP 800 steel microstructure with the strain grade. The variables that can have influence on this kind of analysis methodology have been studied and their effects evaluated. This method has been applied to determine the induced martensite by deformation under conditions of pure shear deformation. Results point that this method allows to state that the microstructure evolution taking place in TRIP 800 steels is not proportional to the strain applied.

Abstract: Laser beam welding (LBW) show clear advantages compared with other techniques, as the low heat input, the high localization ability, the high welding speed, the high flexibility, the high weld quality and the high production rate. However, its applicability to aluminium alloys is limited, as they generally have high reflectivity, high thermal conductivity and low viscosity. In the present study, the laser weldability of four aluminium alloys (2024, 5083, 6082 and 7075) under conduction regime is analysed. High penetration butt welds could be obtained with a High Power Diode Laser (HPDL) under conduction regime. The properties of the weld beads such as the microstructure and microhardness were analysed. A linear function between the input laser fluence and the volume of melted material was obtained for the four alloys.

Abstract: Present work poses, from the methodological point of view, an approach to a case offorging by indentation by means of the application of the Upper Bound Element Technique(UBET), in his development of triangular rigid blocks (TRB). With two approaches of differentnature (Modulate and not Modulate), it tackles the study of the evolution of the necessary minimumenergy to attain the required deformation. The UBET allows a suitable implementation of theboundary conditions of the process, as well as the characteristic of the same, such as the kind offriction or the geometrical considerations, without limit on the flow of material in contrary directionto the applied load by the tool.

Abstract: The analysis of LIF operations is often difficult, especially when several strokes are necessary to obtain the final shape of the part. The use of FE models is highly recommended and it is known that implicit FE models give more robust results than explicit FE models; however, with the former methodology there are several problems that must be faced. With the main goal to extend the analysis capability of LIF operations, some explicit FE models are developed in this paper and results are compared to those obtained by implicit methodology. It can be concluded that taking into account these guidelines, the developed models could be further used in the analysis of multi-strokes LIF operations, where more complicated trajectories are going to be used.

Abstract: Ti6Al4V is the α-β alloy most employed in industry. The modification of its properties can be achieved with conventional heat treatments and/or with laser processing. Laser remelting (LR) has been applied to Ti6Al4V by other authors with excimer and Nd-YAG laser, employing pure argon as shielding gas to prevent risk of oxidation. In the present contribution, LR has been applied for the first time with a high power diode laser shielded with argon to improve the properties of Ti6Al4V. Results showed that remelted samples (with medium energy densities) have higher microhardness and better corrosion resistance than Ti6Al4V base metal.

Abstract: Over recent years, some severe plastic deformation processes have been developed with the aim of obtaining a material with sub-micrometric or even nanometric grain size, such as: ECAE (Equal channel angular extrusion) and HPT (High pressure torsion) among many others. The main aim of this present study is to analyse the upsetting of the 5083 Al-Mg-Mn alloy, which had been previously deformed by ECAE. Different processing temperatures will be used and the final properties of the resulting material will be determined.

Abstract: The use of fiber reinforced polymer (FRP) composites in the aircraft and automotive industries exponentially. Reinforced fibers which are abrasive in nature make it hard to machine by the traditional machining. Dissipation of heat into workpiece which in turn results in enhanced cutting tool wear and damage to the workpiece is the common problems faced in traditional machining of FRPs. Nontraditional machining is favorable to reduce these issues. Abrasive waterjet machining (AWJM) is one of the best choices for machining FRPs. Development in AWJM of FRPs and the current research in this field will be discussed in details. Machining process of FRPs, quality dependents such as surface finish and variable cutting parameters will be addressed. One of main issues in AWJM noise due to high flow rate of water jet will be addressed. The importance of human safety aspects when AWJM is employed will be highlighted. Limitations and challenges in AWJM are presented elaborately.

Abstract: The development of open Additive Manufacturing (AM) technologies, such as the Fab@Home system, has emerged as a freeform approach capable of producing complex three-dimensional objects with a broad variety of materials. The main objective of this work is to analyze and optimize the manufacturing capacity of this system when producing 3D edible objects. A new heated syringe deposition tool was developed and several process parameters were optimized to adapt this technology to consumers needs. The results revealed in this study show the potential of this system to produce customized edible objects without qualified personnel knowledge, therefore saving manufacturing costs compared to traditional technologies.

Abstract: The main disadvantage for industrial application of new processes based on laser surface treatments, such as laser hardening, quenching or precipitation hardening, is the prior experimentation needed to determinate the optimum conditions for processes. The presented work is focused on the development of a tool based on a semi-empirical model to predict accurately the thermal field and thickness of the head affected zone in laser surface treatments in order to avoid the previous experimental setups of this processes. The conventional thermal models are focused on solving the differential equation of temperature field, considering the laser as heat source and thermal properties of each material. However, during the rapid heating treatment processes of metal surfaces are some unknown heat sinks such us metallurgical transformations or a changeable material absortivity that must be taken into account. The model has been adjusted and validated with experimental data for AISI 1045.