Ultrafine Grain Structure Development in Aluminium Alloy by Strain Hardening using CCGP

Severe Plastic Deformation (SPD) processes are for developing ultrafine grained (UFG) structured materials for different Industrial applications. Cyclic Constrained Groove Pressing (CCGP) is a technique, produce fine grained structures in metallic sheets or plates in mass production. The objective of research work is to investigate the influence of CCGP processing on the super plastic behaviour of an Aluminium alloy. Samples in “ascast” materials processed by CCGP with as cast, 1, 2, 3 and 4 passes. Processed Material study for microhardness and Tensile strength mechanical properties test were done for different test specimens. Grain refinement, microhardness and Tensile strength increased with the number of CCGP passes.

Comparison of Experimental and Numerical Study on Superplastic Forming of Rectangular Box Shape using AZ31 Magnesium Alloy Sheet

Super plastic forming has become a feasible process in manufacturing aircraft and automobile parts. Super-plasticity is a property of certain metallic materials which enable them to attain very high elongations (100% and above) without necking under certain conditions. This is assigned to the viscous behaviour exhibited by certain metals and alloys with very fine and stable grain structure at temperatures above half of the melting point. The experimental setup was developed for finding the parametric influences and their effects on super plastic forming. AZ31 Magnesium alloy is most suitable materials for producing more complex shapes using super plastic forming method. The experimental values of pressure, temperature and the thinning, dome height of the super plastically formed specimens were analysed.

Conventional Super Plastic Forming and Multi-attribute Optimization through VIKOR and ANOVA

Super plastic forming is a manufacturing process utilized in the automotive industry like vehicle structures to produce complex geometries of aluminium or magnesium alloy components which cannot be fabricated at room temperature. The technique has proven to be an efficient cost-worthy process in forming various lightweight components for aerospace and medical applications During the process, parameters such as die entry radius, pressure, temperature and material thickness at the sheet die interface greatly influence the metal flow and also depends on product quality. The aim of prsent work is to optimise the conventional super plastic forming process parameters for getting the better quality with proper dimensions of hemispherical cup out of AA2024 sheet. The sheet is placed in a die, which can have a simple to complex geometry depends on the final part to be produced. It is shaped into the hemispherical cup using compressed air. These input process parameters were varied and output parameters such as thickness, maximum height, diameter and minimum forming time of cup were studied and L9 Orthogonal array with a specific end goal to acquire the yield parameters influencing item quality, both VIKOR and ANOVA were assessed.

Development of numerical tool for hybrid manufacturing process for titanium sheet metal forming

The use of titanium in the aerospace industry has grown considerably in recent years in conjunction with the development of composite aircraft. In this way, improving titanium forming has become an important issue for the industry, both for productivity objectives and the ability to deliver basic parts according to the needs imposed by aircraft delivery rates, as well as for cost objectives. Currently, hot forming of titanium parts can be achieved through two processes: Super-plastic forming (SPF) or Hot Forming (HF). The aeronautical industry wanted to develop an innovative process for the manufacture of titanium parts by coupling the HF and SPF processes in order to exploit the advantages of these two technologies. The development of a mixed HF / SPF process will thus not only improve the rates and allow better control of the quality of the formed parts (thickness homogeneity), but also, by allowing forming at lower temperatures, this hybrid process presents a large interest at the energy plan. The study was devoted to the development of a hybrid HF/SPF process, carried out at a common temperature, allowing the “pre-forming” of the part in HF mode and the “calibration” of the part in SPF mode, while respecting a global cycle time compatible with the objectives of the aerospace industry and guaranteeing the quality expected for the final complex part. Improving the performance of the final part requires a development of numerical simulation tool of the forming process. The available simulation tool (ABAQUS/ Standard) must be adapted to define the best simulation strategy according to the simulated parts; moreover, it remains imperative to determine the input data (material behavior laws of titanium alloys) adapted to the cases to be treated (strain rate and process temperature).

Thermo-cycling impact upon velocity choice of titanium alloy super-plastic flow

The modes of the thermo-cyclical deformation of pseudo-α alloys having the super-plastic deformation state under isothermal conditions at temperatures in the field of two-phase state are investigated. The modes for preliminary thermo-processing influencing processing characteristics of VT20 and OT$ alloys, that is, increasing a deformation temperature interval and decreasing processing time are determined.

Influence of Grain Size and Thermo-Mechanical Conditions on the Activation Energy for Super Plastic Flow in Ti-6Al-4V Alloy

The essential objective of this work is to establish the influence of grain size and thermo-mechanical conditions on the activation energy for super plastic flow (QSPF) in Ti-6Al-4V alloy by applying the quantum mechanics and relativistic model (QM-RM) proposed by Muñoz-Andrade, in the framework of the unified physics. The QM-RM allows the direct determination of the QSPF in advanced materials at instantaneous thermo-mechanical material working conditions. By applying, the QM-RM on the experimental results reported previously by some authors, it is shown for grain size of 6.1μm, that the calculated QSPF for grain boundary sliding is about 193 and 178 kJ/mol, at 850°C with an efficiency of power dissipation, η=0.65. These results are in closed agreement with the values of 204 and 174 kJ/mol reported previously for grain boundary self-diffusion energy of α-Ti. Nevertheless, for grain size of 0.6μm the calculated QSPF is 142 kJ/mol at 650°C, with an efficiency of power dissipation, η=0.61. As well, in order to understand the phenomenology and mechanics of SPF in Ti-6Al-4V alloy, the variation of the activation energy with the temperature; stress and strain rate is analyzed in association with coupled mechanisms during SPF, such as grain boundary sliding, cooperative grain boundary sliding and self-accommodation process related to the microstructure. In summary, the results of QSPF obtained in this work, by the QM-RM are in closed agreement with results reported previously by using the theoretical and conventional methodology set up by Mohamed and Langdon.