Effect of Extrusion Conditions on Metal Flow and Microstructures of Aluminum Alloys
T. Ishikawa 1, H. Sano 2, Y . Yoshida 1, N. Yukawa 1, J. Sakamoto 1 and Y . Tozawa 1(1)
1Dept. of Materials Science and Engineering, Nagoya University, Japan
2Sumitomo Light Metal Industries LTD, Japan
1 INTRODUCTION
Study of metal flow in extruded billet of aluminum alloy is fundamental and uful to understand extrusion technology. In particular, investigation of extruded billet skin behavior is indispensable to maintain qualities of extrudates [1]-[3]. In direct extrusion, oxide layer and gregation on the surface of cast billets accumulate in the back end of billet with the progression of extrusion. At the end of extrusion, billet skin begins to flow from back end of billet to the extrudate. Therefore, butt thickness has to be t at the proper value to prevent billet skin from entering extrudates. In direct extrusion, metal flow of billet effects on qualities of extrudates. It is important to make an accurate estimate of skin movement and metal flow of billet.
On the other hand, control of extruded aluminum alloy grain structures is now being driven by many ap
plications, particularly tho with in the automotive industry. Coar surface grain can give ri to a number of problems after forging of aluminum alloys including reduced fatigue resistance, poor machinability and surface finish [4],[5]. Often it is desirable to retain a non-recrystallid fibrous structure to take advantage of the strength increa associated with the work hardening. Becau it is impossible to maintain the fibrous structure over the cross ction, it is necessary at least to obtain uniform and fine recrystallization structure. Control of grain size can be important to maintain the uniform product quality and ensure free from orange peel during cold forming.
In this paper, we focud on two important problems in aluminum alloy extrusion which affect the quality of the products. One is the deformation of skin layer of billet and the other is the control of microstructure of extrudates. Experimentally we extruded two layer clad billet and then obrved the deformation of skin material. And also, we estimate the deformation of skin material of clad billet in FE code DEFORM-2D TM . We compared the results of the FE analysis with experimental results. After it was confirmed that the analytical results were appropriate, the effects of veral conditions on the deformation of billet skin were investigated.
Secondly, the microstructure evolution of aluminum alloy during extrusion was analyzed. Experimentally, we extruded AA2013 billet and obrved the grain structure of cross ction of billet.
And also, we performed FE analysis. By using computer analysis, we can obrve the distribution of strain rate, strain and temperature in the cross ction. We compared the results of the FE analysis with experimental results and investigated a relationship between recrystallization and strain rate, strain and temperature.
2 BILLET SKIN BEHAVIOR
2.1 Extrusion experiment of two-layer clad billet The two-layer clad billet consisting of skin material and core material is ud for the experiment. A6063(JIS) was lected as the core material and A3003(JIS) was lected as the skin material becau their flow stress are similar at high temperature and they could be distinguished easily by different structures after etching. Two types of clad billet with skin material 1.0 mm or 2.0 mm thick were ud in this experiment and their total diameter was 91 mm and their length was 91 mm. Billet became 85 mm long after uptting. Other extrusion conditions are shown in Table 1. The clad billet was heated to 450 ˚C, ram and the container was heated to each experimental temperature with the furnace. Clad billet was extruded until the length
搞笑的美剧Abstract
Study of metal flow in extrusion billet is fundamental and uful to understand extrusion technology. Investigation of behavior of extrusion billet skin and microstructure of products is indispensable to maintain qualities of extrusions. In order to rearch the behavior, experiments and FE analysis of clad billet extrusion were performed. The analytical results of billet skin deformation were similar to that in experiments. Friction between back end of billet and ram affects the deformation of skin and its penetration into billet. Secondly, microstructure of an extruded product is predicted and the condition of recrystallization and grain refinement is revealed.
Keywords:
Extrusion, FEM, Microstructure
Extrusion ratio
5.5Diameter of product [mm]
40
Temperatures [˚C ]Billet &tools:450
Ram speed [mm/c]19C ontainer Diame ter [mm]
94
Container: 20-500Table 1: Extrusion conditions.
Annals of the CIRP Vol. 55/1/2006
of its remainder reaches 21.5 mm, which is about 25 % of the whole billet length. After container was cooled, billets were pushed out. Billet remainder was divided in longitudinal direction and macrostructures in ction were obrved after grinding and etching. Some of the results are shown in Figure 1. From this result, container temperature does not affect the billet skin flow. On the other hand, lubricant condition between ram and billet affect billet skin fl ow signifi cantly.2.2 FEM analysis of skin deformation
Billet with the skin material 2.0 mm thick was ud in the analysis. Length of billet was 85 mm. Figure 2 shows the model of extrusion billet with two layers: core material and skin material. In this model, core material and the skin material are defined as different objects, but their flow stress are both defi ned as A6063 in high temperature. Billet was defi ned as visco-plastic, ram and the container were defi ned as elastic and the die was defi ned as rigid body. Analysis starts from the point where the billet has been filled in the container in order to shorten the calculation time. Analytic
al extrusion conditions are
shown in Table 2. We ud 19 mm/c as the ram speed
in experiment, but in order to bring analysis clo to actual production rate, ram speed was t to 38 mm/c. Figure 3 shows the analysis result showing the effect of the container temperature. Container temperature does not have much effect on billet skin flow as in the ca with experiment. Figure 4 shows the effect of the friction coeffi cient to the billet skin fl ow. It has a signifi cant effect on billet skin fl ow.For further consideration, analysis under 5 more friction conditions, i.e. µ=0.1, 0.08, 0.05, 0.005 and fully sticking were performed. Temperature for all tools and billet are 450 ˚C. Figure 5 shows the skin appearance just before outflow of the skin into extrudates and d indicates the length of remainder at that moment. Smaller d means better yield rate. So, as friction coefficient gets smaller, skin fl ow gets faster and yield rate gets wor. From this result, it is considered that the larger friction coefficient means slower skin flow and better yield rate. Figure 6 shows the calculated results of fully sticking condition. Being different from expectation, amount of d for fully sticking condition got larger than 0.1. From this result, we can say that it is better to make the material skin to slide slightly at the punch surface in order to delay the skin fl ow and improve the yield rate.
3 MICROSTRUCTURE PREDICTION IN EXTRUSION 3.1 Extrusion experiment
AA2013 alloy compositions are shown in Table 3. Billet diameter was 90 mm and its length was 200 mm. Billet became 183 mm after uptting. Billet was heated up to 530 ˚C, die was heated up to 450 ˚C and container was heated up to each experimental temperature, 500 ˚C, 450 ˚C and 400 ˚C. Extrusion experiments under 2 kinds of ram speed were performed. So, we performed 6 different
Core Mat er ial
Cont ainer
Di e
Ram
Skin Mat er
ial
E x t r u s i o n D i r e c t i o n
L
C Figure 2: Analysis model (Clad billet model).Extrusion ratio
5.5Diameter of product[mm]40
Container:20-500Temperatures []Billet &tools:450
Ram speed [mm/c]38Container Diameter [mm]
94
Billet-Ram:0.005-0.1Billet-Tools:=0.5Fri ction co nditions
Core-Skin:
sticking
˚C µ
bec考试费用Table 2: Analytical extrusion conditions.Ram
C o n t a i n e r Ram C o
n t a i n e r
Ram C o n t a i n e r Ram
C o n t a i n e r No.1(20˚C)No.2(200˚C)No.3(400˚C)No.4(500˚C)C o n t a i n e r
C o n t
a i n
e r C o n t a i n
e r C o n t a i n e r
D i e
D i e
D
i e
D i e
tube8asianFigure 3: Skin material shape after 75%vol. extrusion at
each container temperature (FE analysis result).
Figure 1: Experimental results of skin material shape at 75%vol. extrusion (Skin material thickness: 1.0mm).
(a) Room temp., No lubrication
(b) 400˚C
No lubrication
yyt
(c) 400˚C, Lubricated Figure 4: Skin material shape at 75%vol. extrusion at each
friction coeffi cient (FE analysis result).C Ram
Core mat er ial
Skin mat er ial Ram
Die
(a) µ=0.1
(b) µ=0.005
experiments. Container diameter was 94 mm and products diameter was 15 mm (extrusion ratio=39). Extrusion conditions are shown in Table 4. Billet was extruded and product was water quenched. After product was cooled, it was divided in longitudinal direction and macrostructures in s
ection were obrved. Some of the results are shown in Figure 7. The percent values in Figure 7 indicate the percentage of length to extrude radius. From the results, the center part of Figure 7(a), which is a result of slower extrusion speed, did not recrystalli and fi brous structure remained but center part of Figure 7(b), which is a result of faster extrusion speed, recrystallid with coar grain structure. In both results, grain size near the surface becomes smaller. 3.2 FEM analysis
剑桥少儿英语考试延期Figure 8 shows the analysis model of AA2013 extrusion. Billet was defined as visco-plastic, container and ram were defi ned as elastic and the die was defi ned as rigid
Si Fe Cu Mn Mg Cr Zn Al 0.6-1.0
0.40
1.5-
万圣节英文手抄报2.0
0.25
0.8-1.2
0.04-0.35
0.25
Bal
Table 3: Composition of AA2013 (mass%).Extrusion ratio
39Diameter of product[mm]
15
Container:400-500
Billet:530Temperatures []Ram:500Ram speed [mm/c] 1.5,3.0Container Diameter [mm]
94Billet length [mm]200Billet Diameter [mm]
90
˚C Table 4: Experimental conditions.
Figure 7: Macrostructure of the products under each
extrusion condition.Extrusion ratio
39Diameter of product[mm]15
Container:400-500
Billet:530Temperatures []Ram:500Ram speed [mm/c] 1.5,3.0Container Diameter [mm]
94
Billet-Ram:=0.5Friction con ditions Billet-Tools:m=1
Billet length [mm]183Billet Diameter [mm]
94˚C µTable 5: Analysis model.
(c)µ=0.05(d) µ=0.005
Ram
Die
d
Ram
Die
d
Ram
d
Die
C o n t a i n e r
Die
Ram
C o n t a i n e r d
(b) µ=0.08
(a) µ=0.1Figure 5: Deformation behavior of billet skin at each
friction condition (FE analysis result).
Die
d = 19.3mm
d
Ram
Die Figure 6: Deformation behavior of billet skin at fully
sticking condition (FE analysis result).
C
L
69%31%(b) Ram speed 3.0mm/c
Container temp.:500˚C
C L
37%42%21%
(a) Ram speed 1.5mm/c
Container temp.:500˚C
E x t r u s i o n d i r e c t i o n
body. Analysis starts from the point where the billet has been filled in the container. Length of the billet was 183 mm and diameter was 94 mm. We ud same ram speed as the experiment, 1.5 mm/c and 3.0 mm/c. Analytical extrusion conditions are shown in Table 5. Figure 9 shows the strain rate distribution in the product from the analysis results. Strain rate of the red region is over 6.5 /s. Red region in Figure 9(b) covers entire cross ction but there is some blue region around 37 % at center part in Figure 9(a). By comparing this result with the experimental result of Figure 7, it is said that region where strain rate exceed 6.5 /s recrystallis. Percentage of shaded region in Figure 9(a), where strain rate under 6.5 /s, and percentage of red shaded area in Figure 9(a) which is not recrystallid fibrous grain structure part, are almost the same. So it would appear that there is a relationship between strain rate distribution and recrystallization. Figure 10 shows the strain distribution in the product from the analysis results. By comparing this result with the experimental result, it is obvious that recrystallid grain size can be associated with strain distribution. Region wh
ere strain becomes larger than 3.7, which is green shaded part in Figure 10, can be associated with fi ne recrystallid grain pha.This is same as green shaded part in Figure 7. Recrystallid region where strain is smaller than 3.7, i.e. blue shaded part in Figure 10, can be associated with coar recrystallid grain part and this is same as blue shaded part in Figure 7. Percentage of the each shaded areas in analysis result and experimental result are approximately
same, so strain distribution can be related to recrystallid grain size.4 CONCLUSION
In order to investigate the billet skin behavior and the
recrystallization behavior, experiments of billet extrusion and FE analysis were performed. From the results, following conclusions were obtained.
1. Temperature distribution does not affect the skin
material fl ow.2. Friction coeffi cient between billet and ram affects the
skin material fl ow.3. Skin material fl ow is faster when the friction coeffi cient
is extremely small becau the skin slides at the surface of the ram.
4. It is better to make the material skin to slide slightly at
the ram surface in order to improve the yield rate.
5. Strain rate distribution can be associated with
recrystallization. No recrystallid structure will be obtained if the strain rate does not exceed 6.5 /s by lecting the ram speed.
6. Strain distribution can be associated with recrystallid
grain size. The region where strain exceeds around 3.7 is recrystallid with fi ne grain size.
The results have been applied to the actual extrusion operation and high quality products are made effectively.5 References
typical
[1] The Japan Society for Technology of Plasticity, 1992,
Extrusion Process, Corona Publishing, 224-232.[2] Sano, H., Ishikawa, T., Yoshida, Y., 2004, Study of
Metal Flow in Extruded Billet, ET-2004 Proceedings, 47-53.[3] Kaneko, T., Yoshida, Y., Yukawa, N., Ishikawa, T.,
Sano H., 2002, Study of Metal Flow in Extruded Billet, The Proceedings of the 53rd Japane Joint Conference for the Technology of Plasticity, 439-440.[4] Duan, X., T. Sheppard, T., 2003, Simulation and
control of microstructure evolution during hot extrusion of hard aluminum alloys, Materials Science Engineering A, 351, 282-292.[5] Parson, N., Jowett, C., 2005, Control Grain Structure
in Al-Mg-Si Extrusions, ET-2005 Proceedings, 71-80.
Cont ainer
Di e
Ram
E x t r u s i o n D i r e c t i o n
L
C
Billet
Figure 8: Analysis model (Single billet model).
Figure 9: Strain rate distribution in the products under
each condition.(a) Ram speed 1.5 mm/c Container temp.: 500˚C (b) Ram speed 3.0 mm/c Container temp.: 500˚C Strain rate over 6.5 /s
C L
Die
C
L
Die 37%
面首Figure 10: Strain rate distribution in the products under
each condition.C L
C L
(a) Ram speed 1.5mm/c Container temp.: 500˚C (b) Ram speed 3.0mm/c Container temp.: 500˚C Die
Dieleaves是什么意思
Effective strain
杨桃的英文3.1 3.7
40%24%68%32%
