Equal Channel Angular Equal Channel Angular Pressing of High Purity Pressing of High Purity

AluminumAluminum

Julio A. NunezJulio A. Nunez

Chris HovanecChris HovanecDr. Surya R. KalidindiDr. Surya R. KalidindiDr. Roger D. DohertyDr. Roger D. Doherty

Mechanics of Microstructures GroupMechanics of Microstructures Group

Equal Channel Angular PressingEqual Channel Angular Pressing(ECAP)(ECAP)

Deformation process Deformation process that imposes high that imposes high strains with the strains with the benefit of retaining benefit of retaining the cross-sectional the cross-sectional area of the work area of the work piece.piece.

Shear Plane

MotivationMotivation

The likelihood that ultra fine grain The likelihood that ultra fine grain aluminum and its alloys can be produced aluminum and its alloys can be produced by ECAP processing with both increased by ECAP processing with both increased strength and fracture toughness.strength and fracture toughness.

To achieve a more in-depth understanding To achieve a more in-depth understanding of the physical mechanisms behind the of the physical mechanisms behind the evolution of grain size and shape during evolution of grain size and shape during severe plastic deformation.severe plastic deformation.

Social/EconomicalSocial/Economical

Space Shuttle

Dodge Viper

F-22

HighThrust

Weight=Higher Acceleration

10% Reduction/6% efficiency

Properties

Processing Microstructure

Performance

Microstructure = PerformanceMicrostructure = Performance

Two Ways to Strengthen Two Ways to Strengthen MetalsMetals

Precipitation HardeningPrecipitation Hardening

Strain HardeningStrain Hardening

Precipitation HardeningPrecipitation HardeningPrecipitation Hardening Precipitation Hardening is a thermodynamic is a thermodynamic reaction that involves reaction that involves creation of a new phase creation of a new phase changechange– Precipitation Heat Precipitation Heat

Treatment: Treatment: precipitates form on grain precipitates form on grain boundariesboundaries

lower fracture toughness lower fracture toughness compared to strain compared to strain hardeninghardening

Grain Boundaries

Strain HardeningStrain Hardening

Strain Hardening occurs when a ductile Strain Hardening occurs when a ductile metal becomes harder and stronger as it is metal becomes harder and stronger as it is plastically deformed plastically deformed – rolling, compression, and ECAProlling, compression, and ECAP

RollingRollingWidely used for strain hardeningWidely used for strain hardening

Pass a piece of metal between two rollsPass a piece of metal between two rolls– Although imposes strain on the metal, it Although imposes strain on the metal, it

reduces thicknessreduces thickness– Sample thickness limits amount of strain Sample thickness limits amount of strain

inducedinduced

AluminumAluminum

Generally precipitation heat treated Generally precipitation heat treated because of inherent propertiesbecause of inherent properties

Lowers fracture toughnessLowers fracture toughness

Dr. Doherty and colleagues discovered Dr. Doherty and colleagues discovered high solute alloys increase fracture high solute alloys increase fracture toughness when strainedtoughness when strained

ECAPECAP

Same strength as precipitation hardening Same strength as precipitation hardening but higher fracture toughnessbut higher fracture toughness

Rolling Rolling εε =2.3 VS. ECAP =2.3 VS. ECAP εε =10 =10

ObjectivesObjectives

Successfully process high purity Al by Successfully process high purity Al by ECAP to high strainsECAP to high strainsExtract mechanical properties as a Extract mechanical properties as a function of imposed strainfunction of imposed strainExtract mechanical properties as a Extract mechanical properties as a function of microstructurefunction of microstructureValidate the MMG ECAP process through Validate the MMG ECAP process through comparisons of experimental data & comparisons of experimental data & published datapublished data

ProcedureProcedure

Run each sample twice and heat treat at Run each sample twice and heat treat at 450C for 1hr450C for 1hr

Run ten samples to different strains Run ten samples to different strains through route “A”through route “A”

Cut samplesCut samples

Run compression test Run compression test

Perform metallography to measure grain Perform metallography to measure grain size and analyze texturesize and analyze texture

MicrostructureMicrostructure

Metallography is Metallography is the process of preparing samples such that any deform or unrepresented surface is removed so the specimen is ready for analysis.

Grain SizeGrain Size

Texture OIM (measure Texture OIM (measure of crystal orientations).of crystal orientations).

SEM

OIM

Grinding/Polishing•Grinding is done on a spinning wheel with water running on the surface.

•Round SiC grinding paper are used to scratch the surface with all the lines going in one direction.

•Polishing creates a smooth, mirror-like finish.

•Non-abrasive cloth is used and lubricant is added and a diamond suspension which acts as grit.

Different grit papers

Grinding wheel

Cloth, lubricant, and diamond suspension

Mechanical PropertiesMechanical Properties

Theoretically we Theoretically we expect the expect the envelope expand envelope expand to the rightto the right

KIC

σy

Fracture Toughness

Yield Strength

Mechanical PropertiesMechanical Properties

Theoretically we Theoretically we expect the expect the envelope expand envelope expand to the rightto the right

KIC

σy

Fracture Toughness

Yield Strength

ResultsResults

Results from testing will be used to Results from testing will be used to compare data from previous published compare data from previous published findings.findings.If the data correlates, this will validate If the data correlates, this will validate proper technique and give us a base line proper technique and give us a base line for our overall project. for our overall project.

Thank YouThank YouThank YouThank You

DislocationsDislocationsLinear or one dimensional defects where some of

the atoms are misaligned.