Materials Science Forum Vols. 475-479

Abstract: An experimental study on superplastic forming of a front fender of 5182 aluminum alloy is presented in this paper. Based on the shape characters of the front fender and the material experimental results, dies, heater and temperature controller for superplastic forming of the fender are designed and manufactured. The SPF results show the designed processing and dies are reasonable and feasible.

Abstract: Superplasticity and crystallographic orientation distribution of an Al-Mg-Mn sheet subjected to friction stir processing (FSP) have been investigated. The FSP was developed by adapting the concepts of friction stir welding to obtain a fine grain size in a stirred zone. Grain refinement was achieved by the FSP to give a smaller grain size of about 4µm than a value of 26µm in the as-received sheet. The SEM/EBSP analysis of the specimen before and after the FSP revealed a fraction of high angle grain boundaries became a higher percentage of 83% due to the FSP than 75% before. The elongation to failure in the FSPed sample had a maximum value of 361% at 773K and 1.1×10-3 s-1. Further, change in crystallographic orientation distribution is investigated during tensile testing in consideration of deformation mechanism.

Abstract: Friction stir welding is a novel welding technique which has been successfully applied in structure manufacturing of aluminium alloys (including 2XXX and 7XXX). Friction stirring in aluminium alloy welds produces a combination of very fine grain size. This paper deals with the SPF response in 1420 Al-Li alloy welds. The results showed that the friction stir weld could achieve good superplasticity performance. The lateral elongation in the weld could reach 120% and the grain size still remain the same size with little change. And the drawback in the friction weld is the obstacle to fufill the good SPF ability. During the friction stir welding, some oxides or contaminates were stired into the weld in the form of black line. When the weld was experienced superplastic deformation, the crack initiated from the line and finally reach the surface and bottom of the plate. The oxide was formed mainly in the nugget of the friction weld. So the parameters and preparation before welding must be optimized so that the weld can achieve maximum superplasticity performance.

Abstract: As a versatile fabrication process for titanium and aluminum alloys, SPF/DB offers a real potential for revolutionizing aerospace component design. In this paper, the principle, advantages, techno-economics of the process, as well as its application in aerospace industry are introduced. The current trends and the factors relating to the process’s developments are given.

Abstract: The microstructure of friction stir processed AA5052 sheets is investigated using Scanning Electron Microscopy (SEM) and Orientation Imaging Microscopy. The correlation between the generated forces during processing and the microstructure is evaluated. Observations indicate that the finest microstructure are achieved when the plunging forces are at minimum.

Abstract: Titanium alloys sheets have many attractions for the aerospace industry owing to their high strength, low density, heat resistance and other useful properties. Many of the sheet metal structures in airframes have complex shapes and compound curvatures with intricate details. Superplastic forming (SPF), a most recent advancement in titanium sheet forming technology, exploits the excellent characteristic of >1000% elongation potential for the fabrication of complex configurations not achievable by conventional methods. SPF technology can also reduce manufacturing cost by shortening the preparation time, eliminating the need for extensive welding or other joining methods and by reducing the number of manufacturing steps. Consequently, high profit margins may be achieved in serial aircraft production. This paper outlines the research at Israel Aircraft Industries (IAI) of SPF technology and its application in producing complex-shape Ti sheet parts for the new IAI commercial aircrafts, models “G-150” and “G-200”. Examples of both actual and experimental parts are given, together with details of the manufacturing parameters employed. An economical analysis is also included.

Abstract: The complex superplastic forming (SPF) technology applying gas pressure and compressive axial load is an advanced forming method for bellows made of titanium alloy, which forming process consists of the three main forming phases namely bulging, clamping and calibrating phase. The influence of forming gas pressure in various phases on the forming process are analyzed and models of forming gas pressure for bellows made of titanium alloy are derived according to the thin shell theory and plasticity deformation theory. Using model values, taking a two-convolution DN250 bellows made of Ti-6Al-4V titanium alloy as an example, a series of superplastic forming tests are performed to evaluate the influence of the variation of forming gas pressure on the forming process. According to the experimental results models are corrected to make the forming gas pressures prediction more accurate.

Abstract: High strain rate superplasticity has been realised at room temperature for the first time with a ultra fine grained Zn-22wt%Al alloy. Zn-Al alloys have some advantages over low-yieldpoint steels in their low work-hardening rate and high ductility. In addition, Zn-Al alloys are environment-conscious because of no harmful metal like Pb. However, when Zn-Al alloys are subjected to plastic deformation, the strain is localised and local fracture can take place because of their low work-hardening property. In this study, a seismic damper was designed with a Ultra fine grained Zn-Al alloy. As a result, an ecological and high performance seismic damper, the so-called “maintenance-free seismic damper”, has been successfully developed.

Abstract: This paper deals with an analysis of material flow in an extrusion process with a divide flow. The billet material flows easily into the corners of the die cavity and/or the material flow is controlled by the help of the ratio in reduction area, thikness ratio of backward can thickness to forward can thickness. So the influences of this tool geometry and process condition on balanced material flow in a combined forward and backward can extrusion process are explained. The FEM simulation has been conducted in order to investigate the effect of process parameters such as thickness ratio on the material flow. Deformation pattern and flow characteristics were examined in terms of design parameters such as extruded length ratio etc. Based on the simulation results, die pressure exerted on the die-workpiece interface is calculated and anaylsied for safe tooling. Therefore the numerical simulation works provide a combined extrusion process of stable cold forging process planning to avoid the severe damages on the tool.

Abstract: . A novel processing method was proposed to enlarge a partial diameter in the middle of a round bar with an experimental size of 10mm in diameter. To confirm that the processing method is applicable also to shaft with a practical size of 25mm-60mm in diameter for general industrial machine, a large-scale processing machine was developed. Deformation behavior of diameter in a processed part during processing process was made to an expression. The several influences, such as bending angle θ, axial-compressive stress σc, diameters D0, rotation number N of shaft and curvature radius ρ, on the increase behavior of diameter were estimated quantitatively.