what is abnormal grain growth?
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The Effect of Thermal-mechanical Treatment on Abnormal Grain Growth on Friction Stir Welded Al-Li 2195 Richard Wellnitz & Anthony D. Barajas Dr Howard – project superviser. Abnormal Grain Growth. Normal Grain Growth. What is Abnormal Grain Growth?. SAMPLE H. STD. Massive Grains (.5-1 mm). - PowerPoint PPT PresentationTRANSCRIPT
The Effect of Thermal-mechanical Treatment on Abnormal Grain Growth on Friction Stir Welded Al-Li 2195
Richard Wellnitz & Anthony D. Barajas
Dr Howard – project superviser
What is Abnormal Grain Growth?
SAMPLE H STD
Abnormal Grain Growth Normal Grain Growth
Massive Grains(.5-1 mm)
Small Rounded Grains (3-5 microns)
Objective To Find Out
Does Hot rolling have an affect on grain growth?Does cold rolling have an affect on grain growth?Does step heating have an affect on grain growth?
Possible Applications
Other possible applications
Other possible applications in pictures examples of cars trains planes etc.
Presentation Organization
Introduction TheoryMethods and EquipmentChartsDescription of ResultsSummary and Conclusions
Theory
Introducing a process of cold working or cold rolling may inhibit this formation of abnormal grain growth by breaking the structures along the slip plane.
Shifting along the Slip plane
Face Centered Cubic on 1 1 1 plane
The FSW equipment
FSW AT 200 RPM
4 IPM
TOOL ANGLE 3.5 DEG
POSITION CONTROL WITH 0.010 “HEEL PLUNGE
Plate and Oven Anneal Oven Temperatures
0
200
400
600
800
0 20 40 60 80 100
Time, min.
T, F
Plate
Oven
TinitTime to
reach 790
100 54 Toven=810 F200 51 tc=15 min.300 49400 45500 41600 35700 26790 0
ctte
fToTf
TT
Thermal Response of Hot Roll Furnace
t min
T F
0 7811 8386 873
11 88316 88221 90026 869
Grain Initiation Thermal History
750
800
850
900
950
0 10 20 30
time, min
T, F
Actual Thermal History of a Monitored Sample During Grain Initiation
Hot Roll Thermal Chart
750
800
850
900
950
0 5 10 15 20 25 30 35 40 45 50
Time,Minutes
T,F
OvenSample
5 880 81110 878 81115 829 79320 891 78625 932 78430 910 81335 867 81540 892 81945 851 82250 869 817
Sample layout
Cold Work Hot work Step Heating Samples
Bead on Plate down center of plate
Step Heating
Step heating-Initially brought up to 750 F And continually increased by 50 degrees each hour afterwards to 950 F
750 F
950 F
50 F
50 F
50 F
50 F 1 HOUR
1 HOUR
1 HOUR
1 HOUR
Time
Temp
Oven and samples heated to 750 degrees prior to step heating
Standard Samples
STD
H-Heated with hot roll samples
STD-FSW Only
ASAW – FSW and Solution Heat treatment
ASFSW- FSW Only
Rolling
Processing schedules
Hot work- 10%,20%,30%,40%Cold work- 5%,20%,25%,30%
T 1 T 2
% OF REDUCTION
THICKNESS OF SAMPLE
PolishingSamples surfaces were polished with silicon carbide
240 grit
400 grit
600 grit
800 grit
1200 grit
alumina suspension polish to .1 micron
Etching
Samples were etched with
10% Sodium Hydroxide solution – 60 seconds
Rinsed –distilled water
Washed in– 50% Nitric Acid Solution
Rinsed –distilled water
Etching- bringing out the grain
Results of Hot Roll
10%
20%
30%
40%
Reduction
.320
Original
Thickness
Results of Cold Roll
5%
20%
25%
30%
.320
Original
Thickness
Reduction
Conclusions
Substantial Grain growth occurs in Al-Li 2195Hot working doesn’t eliminate or reduce grain growthHot work might actually increase grain growthThere is substantial grain growth reduction above 20% cold rollingStep heating does not decrease grain growth
Suggested additional work
Image analysis for grain size (statistical)Additional cold work between 5% and 20%Further metallurgical testing for hardness toughnessTensile strength ductilityFatigue lifeMicroscopy
Acknowledgements
Bill Arbegast-AMPDr. Stone-METSantosh KoduriK.B. AnandSrikanth Labhala
Eric HendersonTyler EngstromColleen GustafsonCasey AllenBrian Tweedy
Discussion
Why is cold work effectiveAt what point is cold work effectiveDoes hot rolling increase the grain growth