Upload
santhosh-kumar-kodhandapani
View
245
Download
0
Embed Size (px)
Citation preview
8/3/2019 Aluminum MMC
1/22
FRICTION STIR WELDING OFALUMINUM MMC 6092-17.5%SiCP
Tracy W. Nelson*, Dick Lederich**
*Brigham Young University
Provo, UT
**The Boeing Company
Phantom Works
St. Louis, MO
Acknowledgments: Work sponsored by the MetalsAffordability Initiative
Scott Packer
Advanced Metal Products Inc.
Bountiful, Utah
8/3/2019 Aluminum MMC
2/22
OUTLINE
Background
MMCs
Joining MMCs
ObjectivesProcedures
Results
Summary
8/3/2019 Aluminum MMC
3/22
BackgroundAluminum MMCs offer:
Advantages:Low density, high specific strength, and high modulus
High fatigue strength
Better wear resistance
Disadvantages:
Low fracture toughness
Fabrication difficulty
High cost
8/3/2019 Aluminum MMC
4/22
BackgroundWeldability of MMCs is greatly compromised
reaction between second phase and Al matrix isoften detrimental
porosity, cracking, aluminum carbides, etc.
often limited in use because of poor weldability
8/3/2019 Aluminum MMC
5/22
GTAW in 6061-21%B4C
GTAW
Hydrogen induced porosity
Formation of Al4C3Al4C3
10 m2 mm
8/3/2019 Aluminum MMC
6/22
GTAW in 6061-21%B4C
2 mm
20 m
1 m
Shrinkage Porosity
Si
Two-pass weld, ER 4043 filler, Ar shielding gas
8/3/2019 Aluminum MMC
7/22
Objectives
Assess the feasibility of joining 6092-
17.5%SiCp via FSW
Compare weld quality, mechanical properties,
and second phase distribution
Evaluate effects of post weld aging on tensile
properties and failure
Characterize tool wear
8/3/2019 Aluminum MMC
8/22
Procedure Base Material - alloy 6092-17.5%SiCp
0.100 (2.54 mm) sheet; 8 X 24 (20cm X 60cm) panels
heavily oxidized must remove before welding
Weld Procedure Development Choose optimal spindle speed, travel speed
Tool materials evaluated H13 tool steel
Polycrystalline cubic boron nitride (CBN)
Weldment Characterization
Both as-welded and post-weld aged Tensile testing (ASTM E8)
Optical and SEM analyses
8/3/2019 Aluminum MMC
9/22
Weld Parameter Evaluation Parameters evaluated for H13 tool
RPM 202, 545 and 815
IPM 6.4, 11, and 26 Parameters used for further testing 545 rpm and 11 ipm
8/3/2019 Aluminum MMC
10/22
Weld Parameter Evaluation Welds Made with CBN
Tooling No spalling of the surface
Less flash
Better consolidation
Much wider range ofparameters possible
8/3/2019 Aluminum MMC
11/22
Mechanical Properties As welded tensile properties for FSW 6092-17.5%SiCp
Strengths very similar between H13 and CBN (3% difference)
Significant difference in tensile elongation between two tool
materials (87% difference)
Coupon #
0.2% Yield
Stress(Ksi)
Ult. Tensile
Stress(Ksi)
Elong. in 2
in.(%)
Fail. Loc.1=DXZ, 2=AS-
TMAZ, 3=RS-
TMAZ, 4=HAZ
0.2% Yield
Stress(Ksi)
Ult. Tensile
Stress(Ksi)
Elong. in 2
in.(%)
Fail. Loc.1=DXZ, 2=AS-
TMAZ, 3=RS-
TMAZ, 4=HAZ
1 33700 38020 0.85 1 34220 39406 1.63 2
2 31526 35070 0.85 3 32000 37538 2.00 2
3 32500 35398 0.60 1 31800 37707 1.95 2
4 34284 39446 0.90 3 34239 38996 1.35 2
5 31847 37302 1.15 1 32500 37617 1.33 2
6 34000 36643 0.65 1 33400 38589 2.00 2
7 33000 37365 1.45 1&3 33400 37662 2.20 2
8 32800 37382 1.00 1&3 31200 36233 1.50 2
Average 32957 37078 0.93 32845 37969 1.74
Stand. Dev. 994 1402 0.274 1139 999 0.335
H13 Tool CBN Tool
8/3/2019 Aluminum MMC
12/22
Comparison of Tensile Failures Tensile Failure locations
H13 tool TMAZ and DXZCBN tool HAZ
8/3/2019 Aluminum MMC
13/22
Post weld aging to T6 w/o SHT Initial test age at 325F for various times
Oxide mechanically removed
Oxide chemically removed, flash machined after welding
Effect of Post Weld Aging
TMAZ (R side)4.545.832.0As Weld
TMAZ (A side)3.947.934.4325F/2h
TMAZ (A side)2.348.137.3325F/4h
TMAZ (A side)1.848.538.2325F/6h
TMAZ (A side)1.749.039.4325F/8h
TMAZ (A side)0.739.434.6325F/7h
Flash was machined away (.006)1.248.440.9325F/4h
TMAZ (A side)1.438.430.2325F/2h
TMAZ (A side)2.134.824.8As Weld
Comments Failure LocationElong.
(% )
UTS
(ksi)
0.2%YS
(ksi)
Condition
8/3/2019 Aluminum MMC
14/22
Effect of SHT and Aging
Failed in nugget1.151.541.2STA-1
Failed in nugget0.237.0-STA-2
Failed in nugget1.250.340.1STA-3
Failed at root side disbond-23.1-Flash removed; 0.020
removed from root
Failed at root side disbond-26.4-Flash removed (0.004)Failed at root side disbond-30.1-None
CommentsElong.
(%)
UTS
(ksi)
0.2% YS
(ksi)
Description of
Machining
SHT at 1030F for 3 hrs, T6 temper at 325F for 7-8 hours
Rockwell B 77-79, verifying T6
Results
Failure at root side disbond Chemical oxide removal, flash machined after welding
8/3/2019 Aluminum MMC
15/22
Root Side Disbond Failures Lazy Sinterface
Etched dye penetrant and radiograph inspections failed to detect
Originally believed to be oxide stringers, but SEM failed todetect oxides (different etch rate)
Need to pickle materials
mechanical cleaning was insufficient
As welded and Aged Failed Tensile Sample
500 m 500 m
8/3/2019 Aluminum MMC
16/22
Comparison of Particulate Distribution
SiC particulate distribution Distribution in weld is same as in base metal
Base Metal Nugget-H13 Nugget - CBN
15 m
8/3/2019 Aluminum MMC
17/22
Lack of Bonding at Surface Interleaving on top surface of weld in 6092-17.5%SiCp
H13 Welds CBN Welds
250 m 250 m
8/3/2019 Aluminum MMC
18/22
Tool Wear Tool wear after FSW 6092-17.5%SiCp
H13 tool after 6 feet of weld
Loss on diameter of pin (essentially no threads left) Loss of radius on shoulder
not feasible to produce significant length of weld
CBN tool after 20 feet of weld
No measurable wear on any features
H13 tool CBN tool
8/3/2019 Aluminum MMC
19/22
Effects of Tool Wear Degradation of weld quality
Surface of weld spallsPin wear affects penetration and stirring action
8/3/2019 Aluminum MMC
20/22
Typical region
1 mm
Steels
100 mLarger magnification of trailing sideClose to the end of the weld
1 mm
Steels
Fe
Effects of Tool Wear Contamination of weld from tool debris
8/3/2019 Aluminum MMC
21/22
Super Abrasive FSW Tools Cubic Boron Nitride (CBN) and Poly-Crystalline
Diamond (PCD) tools
254 cm of FSW in 6061-25%B4
C 170 cm of FSW in 6061-25%SiC
8/3/2019 Aluminum MMC
22/22
Summary FSW FSW can be used to join this material
As-welded tensile strengths are considerably lower than parent
material. Aging at 250F increases strength 20%at expense of ductility
STA after welding results in strengths that are marginally
higher than direct aging, and 20% lower than parent material
Distribution and size of reinforcement is unaffected Due to severe tool wear, traditional tool steels can only be used for
relatively short welds.
CBN tool materials exhibited no wear in 20 (3 m) of weld in6092-17.5%SiC
CBN tools give better surface finish, wider range of acceptableparameters, no weldment contamination, and better properties.