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element simulation。 The hot processing map is another important approach to describing the hot workability of the metal materials。 At present, the processing maps are mainly based on atomic model and dynamic material model (DMM) [14]。 So far, DMM has been increasingly used in the hot working field because of its practical utility。 DMM was first put forward on the basis of continuum mechanics of large plastic deformation, physical system modeling and extremum principle of irreversible thermodynamics by Prasad et al。 [15]。 The hot processing map can be used for determining the unstable flow zone of the metal materials during hot deformation in order to optimize the process parameters。 So far, it has been widely applied to titanium alloy, magnesium alloy, metal matrix composite and so on [16–22]。

In the present study, the constitutive equation and the proces- sing map of 7A09 aluminum alloy were established during hot deformation。 Furthermore, isothermal precision forging of complex-shape rotating disk of airplane was systematically inves- tigated by means of digitized  technology  based  on  CAD,  CAE and CAM。

2。Experimental  procedures

2。1。Typical forging

Rotating disk of aluminum alloy is an important load-bearing part and is located in the principal shaft of lifting system of airplane。 The rotating disk has two inner ears and five outer ears, in which four outer ears have the concaves, as shown in Fig。 1

(a)and (b)。 In addition, the rotating disk forging must meet the distribution of flow line along the profile in order to guarantee the appropriate load-bearing ability, as shown in Fig。 1(c) and (d)。

2。2。Material

2。3。

Compression test

Hot compression test was carried out on the thermal analog test machine of Gleeble-1500 type。 The compression samples with the height of 12 mm and the diameter of 8 mm were derived from the 7A09 aluminum alloy bar。 The compression samples were covered with the graphitic lubricant before compression test in order to avoid the inhomogeneous plastic deformation due to friction。 During compression test, the compression samples were

heated to a certain temperature at the heating rate of 1 1C s−1     and

then were held for 3 min。 Then, the compression samples were compressed by the deformation degree of 60% at the   temperatures

ranging from 300 1C to 460 1C and at the strain rates ranging  from

0。01 s−1 to 10 s−1, and subsequently were quenched into the water at room temperature in order to keep the original microstructures of the compressed samples。 All the compressed aluminum alloy samples were cut along the longitudinal direction by means of electro-discharge machining (EDM) and then were made into the metallographic specimens。 All the metallographic specimens were etched in a solution containing 1。3% HNO3, 0。4% HCl, 0。3% HF and 98% H2O by volume fraction and subsequently were characterized by XJG-05 optical microscope。

3。Digitized  design  and manufacturing

Digitized design and manufacturing of isothermal precision forging of rotating disk mainly deals with establishment of constitutive equation, construction of hot processing map, computer-aided design (CAD), computer-aided engineering (CAE) and computer-aided manufacturing (CAM), and the flow chart

Table 1

Chemical composition of 7A09 aluminum alloy (%, mass fraction)。

7A09   aluminum   alloy   bar   was   used   as   the experimental