Void Behavior of Al-Mg Alloy During Dynamic Recrystallization Induced Superplasticity

China Nonferrous Metals Institute Liu Teng Liu Bing 2. Lei Yi Liu Zhiyi. University of Petroleum East China Electromechanical Engineering Department. Dongying 257062; 2. East China Department of Applied Physics, University of Petroleum, Dongying 257062, China Abstract The supervising man made super-plastic deformation with one elbow and found abnormalities; Naru. That is to say, the evolution law of the jin-kao wave type with empty truths. Through the comprehensive analysis of the microstructure characteristics and mechanical properties curves, it is believed that this special void evolution rule is mainly caused by dynamic recrystallization, that is, dynamic recrystallization has an inhibitory effect on the growth of voids. Through quantitative image analysis of the topography of voids, a new void evolution model has also been obtained.

In recent years, dynamic recrystallization induced hyper-conservatism has attracted people's attention. However, research on the behavior of dynamic recrystallization induced superplastic voids. In particular, the effect of dynamic recrystallization on void behavior is rarely studied in plasticity. Focused on studying the behavior of a hole. And found. During superplastic deformation. There is a close relationship between dynamic recapitulations. Based on this understanding. Include specific experimental data. The existing hole growth tax model was revised.

1 Experimental materials and methods The chemical composition of the two kinds of village materials used in the experiment was 0181. The two kinds of village materials were poured and cast into 45-gauge gold ingots after being ironed and then thinned to 35 crimes by machining. The alloys were homogenized on 43,12, 300 hot-rolled to 20,250, warm rolled to 20 rolls. 200 warm rolled to. 8. The finally obtained rolling plate is cut along the rolling direction into a tensile sample. Winter 1 tensile experiment. The 8032 unloading section was twisted on a temperature-stretching stretcher, and the stretching direction D 016 was also 6 祀 coinciding with the dairy direction. Temperature error ±1. Insulation of the sample before stretching. 1. Immediately after the completion of stretching, water quench cooling. Observe the low-order morphology of the cavity with a metallographic microscope. Measure the size of the grain size with the average length of cut-length method 4800. Empty high profile and fracture appearance. Quantitative image analysis was performed using a 26-image analyzer from Germany.

1 Fund Project China National Petroleum Corporation Young and Middle-aged Innovation Fund Project 2 Experimental Results and Analysis 2.1 Determination of Optimal Deformation Conditions Tensile is performed at different temperatures and strain rates, and the tensile condition with the highest elongation is the highest. Good deformation conditions. The best deformation condition of the gold-like gold was 3,13.33 44=251. The best deformation condition of the eight alloys was the initial grain before the two types of alloys were weaved. 2.2 The void nucleation angle at the grain boundary was 4 Small is a 3 PCT photograph of the void nucleation at the beginning of superplastic deformation. It can be clearly observed that the void nucleates along the vicinity of the phase particles.

During superplastic deformation, grain boundary sliding is a major deformation mechanism.

In the corner grain boundaries and near the phase particles, the grain boundary sliding is not easy to perform. If other coordination mechanisms cannot complete the stress concentration in these parts, then smaller cavities, ie, hollow nucleation, are generated in these parts. The results of the observation of void nucleation and the theory of cavity nucleation of the superplasticity theory are partly in evidence.

2.3 Growth and Evolution of Voids There have been studies on the growth and evolution of voids. Observe that the number of voids monotonically increases with the increase of deformation. Through mathematical derivation, the index of void area can be exponentially related to the true strain. 1412. The author of this article is researching, the relationship between the evolution of voids and the dependent variables. Anomalies were found. That is, at the initial stage of deformation, the number of voids increases slightly with the increase of deformation. When a certain amount of strain is reached, the number of voids is not only not long, but is gradually reduced along with the increase of the strain amount and reaches a low value. With the amount of deformation, plus, and gradually from the trough, large, showing a wave-like evolution.

The void shape of the dependent variable, and the specific numerical value of the void area fraction obtained from the quantitative image analysis are listed in the strain test at a fixed number, and the real milk from the quantitative change relation curve 7 of the raw milk produced by the towel.

Tension curve. Through comprehensive analysis of the organizational evolution and mechanical tensile curves, we believe that such voids are suppressed within the range of the fixed strain. It can be seen that the dynamic recrystallization occurs mainly in the vicinity of the angular grain boundary and the first phase particles, and the nucleation site of the cavity base wood phase 4 with the dynamic recrystallization proceeds. In these areas, deformations are easily coordinated and the stress concentration is reduced due to the appearance of new fine grains. As a result, the driving force of nucleation and growth of the cavity is greatly weakened, and void nucleation and growth are inhibited. From the tensile curve and strain, the true strain where sufficient dynamic recrystallization occurs also corresponds to the true strain where the evolution of the void is suppressed. Variational principle and +1 factory method. The long fire condition of the isolated voids in the material during superplasticity and stretching is deduced, and the true strain of the relationship between the radius growth of the isolated voids and the true strain is obtained; the void radius corresponding to 8, is corresponding to the void radius of 6; Material related constants.

In the process of derivation of the above equation, the authors decomposed the superplastic rheological velocity field reasonably, calculated the evolution rules of each part, and finally superimposed and used the variational principle and the 1 ton 1 he 2 method for extrapolation. . However, Formula 1 also has obvious deficiencies. First of all, it only considers the growth of a single cavity, but ignores the restrictions on the growth of neighboring voids and grain boundaries in the actual structure. Second, Formula 1 only considers the induced cavity growth. The factors, but there are still many bridges and inhibitory factors in the actual printing of the 3 plants, such as the reordering of the grain 5, as well as the dynamic recrystallization mentioned above. From a similar relationship, such as Formula 2 fraction; void area fraction corresponding to 6; material-dependent constants.

We mentioned earlier that there is a deficiency in Formula 1, because the same original spider causes the 2+ solvability. The analysis of the 4th choice of empty holes is based on the analysis of 纟 1 result in order to compare the bodies. The curve of Formula 2 also shows 7. The use of watts into the mark must therefore be corrected for the edge of the equation, but the logarithm is then linearly related to the logarithm, and the quantitative image analysis results are processed and a relation curve is plotted. It was found to have subcurve characteristics, therefore. Formula 2 can be modified for the following constants associated with the material.

According to the experimental data in 7, taking into account the sentence =, we get the undetermined coefficient in Equation 3 by regression. For alloys = 0, D These coefficients are entered in Equation 3 and the calculated theoretical data is shown in dashed lines in 7. It can be seen that the theoretical value is basically consistent with the experimental value.

Analytical formula 3 shows that the items of the term are the same as the total meaning in the formula, which reflects that the number of voids in the initial stage of deformation is small and approximately equal to the situation of independent development. The order of the items is negative because the coefficient is negative, reaching 6 When the numerical value is fixed, it will show the effect of inhibiting the growth factor of voids, which is mainly the function of dynamic recrystallization; the term of the second order plays a significant role when it is larger, and it can be considered as the embodiment that the Langkong dong is connected and grows up quickly after super calling deformation. .

The evolution of voids in superplastic deformation is the combined effect of mutual restraint and mutual coordination between these factors. In this way, formula 3 has a wider scope of use and is closer to the actual evolution of the void. It also has important guiding significance for the formulation of superplastic forming technology. It uses Type 3 to study the evolution law of the material to be processed, find the strain amount when the number of voids is the lowest, and use this strain to perform the actual superplastic forming process. The best use of parts is achieved.

2.4 The hollow connection and the severing site are connected by a hollow connection. The appearance of the ridge can be played by the shange. The vacant hole is mainly connected along the longitudinal direction of the dairy. After the vertical connection has reached a certain degree, the transverse direction of the vertical rolling direction also occurs, eventually resulting in the fracture of the sample.

3 Conclusions In the study of dynamic recrystallization-induced superplasticity, the evolution of void growth is not monotonous and long with the strain, but rather it is a wavy evolutionary law. This kind of void is inhibited at some stage of deformation. It is due to the occurrence of dynamic recrystallization. The dynamic recrystallization occurs preferentially in the corner grain boundary and near the phase particles, which makes these parts modify their own cavity growth model, and gives a more general form. Thanks to Professor Meng Liping of Teacher of the University of China and Professor Wang Jinghong of East China University of Petroleum for their support. And thanks.