a b s t r a c t  Isothermal precision forging of complex-shape aluminum alloy rotating disk of airplane was system- atically investigated by means of digitized technology based on computer-aided design (CAD), computer- aided engineering (CAE) and computer-aided manufacturing (CAM)。 The constitutive equation of 7A09 aluminum alloy under hot compression was established in order to understand the flow behavior of the metal material during isothermal precision forging。 7A09 aluminum alloy frequently exhibits dynamic recovery in the case of low strain rate, while it can also be characterized by dynamic recrystallization in the case of high strain rate。 According to dynamic material model, the hot processing map of 7A09 aluminum alloy was obtained to optimize the process parameters which lead to the stable flow of the metal material during isothermal precision forging。 Based on the different preforms, finite element method (FEM) was used to simulate the metal flow and predict the forming defects during isothermal precision forging of rotating disk。 By controlling the metal flow, the high-quality rotating disk forging was manufactured on the basis of the proper preform through digitized technology。 The simulated results are in good accordance with the experimental   ones。82588

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1。Introduction For the purpose of meeting the requirements for light weight in the aerospace field, aluminum alloy forgings are usually designed based on the integral structure with complex shape。 Furthermore, they are characterized by high dimension accuracy, good mechan- ical properties and perfect flow line distribution。 In general, the complex-shape aluminum alloy forgings possess the lightening structures, such as high rib, long ear, thin web, thin wall and so on。 The lightening structures lead to the rapid dissipation of heat quantity during forging and thus have an adverse influence on   the

formability of the forgings。 In addition, aluminum alloy usually have a narrow forging temperature interval of about 70 1C。   There-

fore, too low forging temperature or too long forging time leads to the rapid drop of the temperature in the forging preform and thus results in the increase in the deformation resistance as well as the decrease in the material plasticity。 Consequently, the finished forgings frequently possess some defects, such as coarse grains, cracks, folding, underfilling and so on    [1–3]。

Isothermal precision forging is an advanced plastic forming process, in which the dies are heated to the approximately same temperature as the forging and the forging temperature is    almost

n Corresponding author。 Tel。: +86 13936266338; fax: +86 451 82519952。

E-mail address: jiangshy@sina。com (S。 Jiang)。

constant in the process of forging。 As a candidate for producing a net shape or at least a near-net shape workpiece, isothermal precision forging has been increasingly used to form light materi- als such as aluminum, magnesium and titanium alloys with small forging temperature range。 As compared to conventional bulk forging, isothermal precision forging has many advantages, such as uniform temperature distribution, low deformation load, high material plasticity, small machining allowance and so on [4–8]。 However, the optimization of the process parameters plays an important role in obtaining the high-quality forgings during isothermal precision forging。 In general, the digitized technology becomes a candidate for cost reducing and time saving during isothermal precision forging。 The digitized technology deals with the integration of computer-aided design (CAD), computer-aided engineering (CAE) and computer-aided manufacturing (CAM)。 In particular, as an important simulation and prediction instrument, finite element method (FEM) plays a significant role in  the digitized technology [9–13]。 In addition, the knowledge for flow behavior and hot workability of metal materials lays the founda- tions for optimizing the isothermal precision forging process。 The constitutive equation is an important approach to understanding the flow behavior of the metal materials during hot working。 On the one hand, the constitutive behavior of the metal materials during hot deformation can be used for understanding dynamic recovery and dynamic recrystallization。 On the other hand, the constitutive  equation  can  become  a  material  model  for       finite