grain refinement of magnesium alloys by conform: a...
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CANMET-MTL
May 11, 2011Hamilton, Ontario, Canada
Grain Refinement of Magnesium Alloys Grain Refinement of Magnesium Alloys by CONFORM: A Continuous Severe by CONFORM: A Continuous Severe
Plastic Deformation Route?Plastic Deformation Route?
Youliang He Jian Li Robert Eagleson
CANMET-MTL, Natural Resources Canada
Youliang He, Jian Li, Robert Eagleson, Pei Liu, Ruby Zhang
Fei Gao, Baoyun Song, Rong Fu, Guiming WuDalian Jiaotong University P R ChinaDalian Jiaotong University, P. R. China
Lan JiangMcGill University
CANMET-MTL
What is Severe Plastic Deformation? Why SPD?
• Large Deformation Strain: > 3• No Dimension Change After Deformation • Normally a Repeatable Process• Normally a Repeatable Process• No Fracture or Damage to the Workpiece• Batch & Continuous Modes
Fabricate Ultrafine or Nano-Structured Bulk Metallic Materials.
Achieve Favourable Properties: High Strength at Room Temperature and/or Superplasticity at Moderate Temperatures and High Strain Rates.
Commercial Products: Sputtering Targets, Dental Implants, Fasteners, …
Materials Processed: Al, Mg, Cu, Ti, Steel, …
Significantly Refined & Uniform Microstructure/Nanostructure
CANMET-MTL
Severe Plastic Deformation: Batch Operation Mode
ECAP HPT CEC TE
• Equal Channel Angular Pressing
• High Pressure Torsion
Good Grain Refining Effect Ultrafine or Nano Grains
Possible• Cyclic Extrusion
Compression• Twist Extrusion
M lti Di ti l F i
Batch Operation ModeSmall Work PieceLow Useful Material Rate
• Multi-Directional Forging• etc. R. Z. Valiev et al., JOM, 2006
CANMET-MTL
Severe Plastic Deformation: Continuous Operation Mode
• Repetitive Corrugation & Continuous Operation:
RCS ARB
p gStraightening
• Accumulative Roll Bonding
pHigher Efficiency
Large-Size Sheets PossibleCracks (Edge or Surface)
• Continuous Confined Strip Shearing
• etc.
Inhomogeneous Thickness Reduction Surface Treatment
R. Z. Valiev et al., JOM, 2006
CANMET-MTL
Severe Plastic Deformation: ECAP + Continuous Feeding
RollerZhang et al 2006
Shoe
Feed stock
RollerZhang et al., 2006
Wheel
AbutmentAbutment
ECAP with Continuous
Feeding
ECAP C f
• Large Shear Strain
ECAP-Conform
Zhu et al., 2006
CONFORM
Large Shear Strain• Hydrostatic Pressure
Srinivasan et al., 2006
CANMET-MTL
Continuous Extrusion Forming: A Combined Deformation Process
Roller Wheel Shoe
AsymmetricRolling Cu
Shear
ECAP Al
Abutment
Extrusion
Friction force as driving Invented in UK Maximum Extrusion
Materials:
Friction force as driving force: low energy consumption
High production rate Continuous production
Invented in UKAtomic Energy Authority in 1970’s
Maximum Extrusion Width: Al ~130 mm, Cu ~320 mm Maximum Product Area: Al ~13000 mm2Materials:
Al, Cu, Pb, Zn, Mg Continuous production Low scrap levels
Al ~13000 mmCu ~6400 mm2
CANMET-MTL
CONFORM: A Continuous Severe Plastic Deformation Route?
T. Erlien et al, NANOSPD3, 2005
Higher Effective Strain than ECAP C ti O ti
CONFORM ECAP
Continuous Operation Already Commercialized Various Product Shapes
Not Widely Recognized YetMore Research NeededMore Research Needed
CANMET-MTL Application to Magnesium Alloys (AZ31)
8 mm
Extruded Cast
Feedstock Cast Microstructure
Both cast and extruded rods can be used as feedstock
CONFORM Machine
Both cast and extruded rods can be used as feedstockHeating of the feedstock and the die chamber neededOne pass CONFORM extrusion onlyNo heat treatment after CONFORM
CANMET-MTL CONFORM Extruded AZ31 Rods
From cast rods
Φ5 mm
From cast rods
Φ7 mm
From extruded rods
Φ5 mm
Meters long product successfully producedg p y pSurface finish depends on the feedstock, heating temperature & extrusion speedExcellent surface finish when extruded rods were used as feedstock
Produced by a Commercial CONFORM Machine Designed for Aluminum
CANMET-MTL Grain Refinement
Feedstock~150 m
Near Surface~1.5 m
Center~2 m SEM
10 µm
2 m
Cross
Significant Grain Refinement: ~150 m to ~2 m
µ Cross Sections of
the Rod
CANMET-MTL
Microstructure Characterization: High Resolution SEM
Grains in Submicrons
Near CenterNear Surface
Grains in Submicrons
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Microstructure Characterization: SEM-EDS
A
A A B
B
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Microstructure & Texture Characterization: EBSD
ED
Inverse Pole Figure Map: Extrusion DirectionInverse Pole Figure Map: Extrusion Direction
Near Center, Average Grain Size: ~1.0 m
CANMET-MTL AZ31 Textures: CONFORM VS. ECAP
0001ED
0121
3121 0001
1102
<0110>
0001 ED 00012311 0121
ED0001
0110{0001}
EDmax=14.457Y
1110
Janecek et al, J. Mat. Sci. , 2010X
CONFORM,Near Center
Basal Prismatic Pyramidal
ED
0001
ED 0001 ED 0001 ED 0001
Contours: 1, 2, …, 10 Contours: 1, 2, …, 10 Contours: 1, 2, …, 10 Contours: 1, 2, …, 15
ExtrusionECAP-1 Pass
ECAP-4 Passes
ECAP-12 Passes
CANMET-MTL
Microstructure & Texture Characterization: EBSD
ED
30 µm
Inverse Pole Figure Map: Extrusion Direction
Near Surface, Average Grain Size: ~0.92 m
CANMET-MTL AZ31 Textures: CONFORM VS. ECAP
0001ED 0001
ED 0001
ED
0001
0121
3121 0001
1102
<0110>
2311 0121
EDmax=6.037YED
0001 0110{0001} 1110
Janecek et al, J. Mat. Sci. , 2010XCONFORM,Near Surface
Basal Prismatic Pyramidal
ED
0001ED 0001 ED 0001 ED 0001
Contours: 1, 2, …, 10 Contours: 1, 2, …, 10 Contours: 1, 2, …, 10 Contours: 1, 2, …, 15
ExtrusionECAP-1 Pass
ECAP-4 Passes
ECAP-12 Passes
CANMET-MTL
Superplastic-like Deformation Achieved by one Pass CONFORM Extrusion
Strain rate: 3.3×10-4 s-1
T = 473 KTo Achieve Superplasticity in Mg Alloys
Strain rate:
Small Grain SizesUniform MicrostructurePreferred Orientations
12.7 mm
St a ate1.0×10-4 s-1 Relatively Low Strain Rates
Appropriate Deformation Temperature
3.1 mm
Extrusion CONFORM- 1 Pass ECAP: Multi-PassesGrain size ~15 m ~2 m ~0.7 m
C-axis ^ ED ~90 40~90 40~50C axis ED 90 40 90 40 50Elongation ~100% ~200% > 460%
CANMET-MTL
Inhomogeneous Microstructure after 1 Pass CONFORM
Near CenterNear Surface Near CenterNear Surface
Multiple-pass processing: uniform microstructureHeat treating after CONFORM Optimization of the processing parameters
CANMET-MTL Summary & Conclusions
Successfully Produced Long Wrought AZ31 Mg Alloy by CONFORM
Significant Grain Refinement from Cast Structure of ~150 µm to 1~2 µm
Superplastic-like Deformation Behaviour Observed in CONFORM Extruded Samples Observed in CONFORM Extruded Samples
Non-uniform Microstructure and Heterogeneous Texture in the Cross SectionHeterogeneous Texture in the Cross Section
An Alternative Forming Method to Mg Alloys
CANMET-MTL
Thank YouThank You
CANMET-MTL Microstructure Characterization: FIB
Significant Grain Refinement: ~150 m to ~1 m
CANMET-MTL
CANMET-MTL Future Work
Processing other Mg alloys by CONFORM
Microstructure characterization and
mechanical properties testingg
Heat treatment after CONFORM
Multipass CONFORM extrusion to produce Multipass CONFORM extrusion to produce
uniform & ultrafine grained
i t tmicrostructure
Texture measurements and analysis
Modeling the CONFORM process