Project graduation (2)Effect of Thermo-Mechanical Treatment (TMT) on Hardness

and Mechanical Properties for Heat-Treated Al-Mg-Si (6082) and Al-Cu-Li-Zr (8090) alloys:

Experimental Correlation Using (DOE) Method using Minitab Software

By: 

Abdullah alshehriYousif albalawyAli alshahrani

Supervisor : 

Dr. Saleh A. Al Kahtani Dr. Mahmoud M.Tash  

College of Engineering 

IntroductionThermomechanical treatment is one such combination of heat treatment and mechanical working, which yield high strength materials, an improvement in fatigue, creep, corrosion resistance and fracture toughness coupled with good formability. TMT is applicable to both ferrous and non-ferrous materials. For non-ferrous alloys, TMT is commonly applied to the age harden able alloys.

The process consists of plastic deformation of alloys followed by aging treatment. This is in contrast to TMT of steels, which entails plastic deformation with simultaneous phase transformation. Different types of steels (carbon steels and low alloy steel, low and medium alloy high strength steels, mar aging steels, tool steels and high-speed steels) have been successfully subjected to thermomechanical treatments. Greater mechanical strength and an increase in toughness as well as dimensional stability are obtained with such treatment.

The objective-The effect of heat- treatment (TMT) on the aging

and mechanical behavior of Al-Cu-Mg-Li-Zr and Al-Mg-Si alloys (8090 and 6082) are investigated i.e. the combined effect of cold work and aging parameters on the hardness of heat-treated 6082 and 8090 alloys are analysed.

-Correlation between metallurgical parameters, hardness and mechanical properties of Al-Cu-Mg-Li-Zr and Al-Mg-Si alloys (8090 and 6082) using Mintab software are investigated .

-Correlation between the hardness results and the different metallurgical factors for these alloys at both quantitative and qualitative are analyzed.

Physical Composition of Alloys 8090 and 6082

Chemical Composition of Alloys 8090 and 6082

Alloy Cu Mg Li Ti Si Fe Zr Mn Al

8090 1.3% 0.9% 2.4

%

---- 0.2% 0.3% 0.1

%

---- Bal

%

6082 0.1% (0.73-

0.75%)

---- 0.01

7%

(0.91

-

0.93%)

0.39% ----- 0.5

%

Bal

RESULTS AND DISCUSSIONS 8090

(a)

(b)

Variation in alloy strength

(hardness (HV) as a

function of heat treatment

conditions.

RESULTS AND DISCUSSIONS 8090

(a)

(b)

Variation in 8090 alloy

strength (UTS (MPa, 0.2%

offset Yield strength and %

elongation) as a function of

heat treatment conditions

Residual

Pe

rce

nt

50250-25-50

99.9

99

90

50

10

1

0.1

Fitted Value

Re

sid

ua

l

120906030

50

25

0

-25

-50

Residual

Fre

qu

en

cy

4530150-15-30-45

80

60

40

20

0

Observ ation Order

Re

sid

ua

l

400350300250200150100501

50

25

0

-25

-50

Normal Probability Plot of the Residuals Residuals Versus the Fitted Values

Histogram of the Residuals Residuals Versus the Order of the Data

Residual Plots for HV

RESULTS AND DISCUSSIONS 6082

Te

rm

Standardized Effect

BC

C

B

A

AB

E

DF

D

DE

EF

AD

F

76543210

1.965Factor

AT 0CE CW3AATF An.t min.

NameA CW1BSHTB PA T 0CC PA t h

D

Pareto Chart of the Standardized Effects(response is HV, Alpha = .05)

RESULTS AND DISCUSSIONS 6082

(a) (b) (c)

(d) (e) (f)

Factorial and ANOVA Plots (main effect plot and interaction effect plot) (a, b) Normal

Probability plot and Pareto chart of the standardized effects for the

hardness data having a confidence level of 95%. (c, d) Main effects plot for

the mean values of hardness (HB). (e, f) Interaction plot for the mean values

of hardness (HV) data.

RESULTS AND DISCUSSIONS

CONCLUSIONS

1-Aging carried out for the Al-Cu-Mg-Li-Zr alloy under investigation, revealed that at 170C with intermediate cold work of 50% reduction yields peak hardness at 10 hours .

2 -Aging carried out for the Al-Cu-Mg-Li-Zr alloy under investigation, revealed that at 385C with intermediate cold work of 27-50% reduction yields peak hardness at (15-20 minutes). This could be attributed to bands of fine precipitates, which appear in those specimens.

3-Optimum mechanical properties (strength and ductility) can be attained for LTMT specimens aged at 170C for 10 hours with cold work of 50% reduction. This could be attributed to the recovery and recrystallization effects