A model approach to metals

A model approach to metals

Wei SHA
Professor of Materials Science
3 May 2006

Other materials
Metals
The for
Not
most
theimportant
same jobs
materials

Microstructure
Big

Small

Microstructure

Heat treatment: steel hardness and Al precipitation

60

Hardness, HRC

55
50
45
40

440°C
480°C
500°C
540°C

35
30
25
0.0625 0.125 0.25


0.5

1

2

4

8

16

Ageing Time, h

Guo, Sha, Vaumousse, Acta Materialia, 51, 2003, 101.

32

64


Mechanical processing
Rolling, forging, ball milling

Gasar
Gas-reinforced metals

Drenchev, Sobczak, Malinov, Sha, Materials Science and Technology, 22, 2006, in press.

Computer software systems

Predicting microstructures
Predicting properties
Predicting the effect of metal processing

Modelling methodologies

1) The Johnson-Mehl-Avrami method and its adaption to
continuous cooling and heating
2) Finite element method

3) Phase field method
4) Atomistic simulation
5) Neural network method
6) Surface engineering products

Neural network
Natual
3

Neuron

Artificial
Input
Layer

Hidden
Layer

Output
Layer


2
5
1
4

Neural Network

The human brain contains
1010 – 1011 neurons

X1
0.345
….
….

Training data set
INPUTS
OUTPUTS
X2

X3
X4
Y1
Y2
-0.701 1.000
0.002
0.678 -0.243
….
….
….
….
….
….
….
….
….
….

Malinov, Sha, McKeown, Computational Materials Science, 21, 2001, 375.


Titanium alloy
Phase transformation
970
5

5

10
15
20
25
35 30
40
50 45
910
55
70 60
65
85 75 80
90

95
880

T (oC)

940

5

10
15
20
25
30
35
40
50 45
55
60
70

75 65
85 80
90
95

10
15
20
25
35
50
70
85

850

820
10
T
Fr3


20

30

30
40
55
75

90
95

40

45
60

1


65

80

50

Cooling Rate (oC/min)

Malinov, Guo, Sha, Wilson, Metallurgical and Materials Transactions, 32A, 2001, 879.

Example of simulation and monitoring
Nucleation and growth of the  phase in Ti6242

Furnace

Time-temperature path

In-situ monitoring

The Model

Malinov, Katzarov, Sha, Defect and Diffusion Forum, 237-40, 2005, 635.

SM_Monitoring.exe

Modules and graphical user interfaces
Simulation and modelling of different correlations
Composition-processing-temperature-mechanical properties

Fatigue life

CCT diagrams

Malinov, Sha, Computational Materials Science, 28, 2003, 179.

TTT diagrams

Microhardness profile

Gasar
Pores
• Heat conduction
• Gas diffusion

Drenchev, Sobczak, Sha, Malinov, Journal of Materials Science, 40, 2005, 2525.

1) Pass the 9 dots with
3 changes of direction

2) Plant 10 trees in 5 lines,
each line having 4 trees



Industrial applications
Optimization of the alloy composition
Find

Optimisation
Criteria

Alloy composition with
max strength at 420°C

Fix
Loops for
Heat Treatment

Trained
Neural
Network

Solution

Heat treatment = Annealing
T = 420°C
Sn, Cr, Fe, Si, Nb, Mn = 0; O = 0.12

Loops for
Temperature
Loops for
Alloy Composition

Vary
Al, Mo, Zr, V

Solution
Al = 5.8; Mo = 7.3; Zr = 5.2; V = 0
Tensile strength (420°C) = 932 MPa;
Yield strength = 665 MPa;
Elongation = 10%;
Modulus of elasticity = 94 GPa;
Fatigue strength = 448 MPa;
Fracture toughness = 101 MPa m 1/2

Malinov, Sha, McKeown, Computational Materials Science, 21, 2001, 375.

Industrial applications
Centrifugal casting process of composite

Drenchev, Sobczak, Malinov, Sha, Modelling Simul. Mater. Sci. Eng., 11, 2003, 635.

Industrial applications
SiC particle distribution during casting of Al alloy

radius r

0s

radius r

15 s

vol.
fraction

vol.
fraction

radius r

5s

radius r

20 s

vol.
fraction

radius r

vol.
fraction

radius r

10 s

vol.
fraction

vol.
fraction

25 s, completed

Drenchev, Sobczak, Malinov, Sha, Modelling Simul. Mater. Sci. Eng., 11, 2003, 651.

Industrial applications
Hot spot and gas cavity in centrifugal casting

Hot spot

Gas cavity

Drenchev, Sobczak, Malinov, Sha, Modelling Simul. Mater. Sci. Eng., 11, 2003, 651.

Acknowledgements
Postdoctoral RA, PhD students, visiting scientists

• Savko Malinov, School of Mechanical & Aerospace Engineering
• Ivaylo Katzarov, School of Mathematics & Physics
• Zhanli Guo, Sente Software, England
• Ludmil Drenchev, Bulgarian Academy of Sciences
• Jerzy Sobczak, Foundry Research Institute, Poland