semi-solid metal processing

Semi-solid Metal (SSM) Processing A New Approach to Metal CastingBy

Dr. Muhammad Kamran

Semi-solid Metal processing by Dr. Muhammad Kamran

April 30, 2009Semi-solid Metal processing by Dr. Muhammad Kamran*IntroductionDiscovered at MIT in 1971During study of hot tearing of steel during solidificationModeled by Sn-15Pb alloy using Coeutte Rheometer

Semi-solid Metal ProcessingNon-dendritic structureSolid-liquid regionSuitable fraction solid

Property exploited isRheologySteady state rheology (Rheology)Transient state rheology (Pseudoplasticity)Time dependent rheology (Thixotropy)


April 30, 2009Semi-solid Metal processing by Dr. Muhammad Kamran*Evolution to Non-dendritic MicrostructureUnder Forced ConvectionFragmentation of primary dendrites byRoot melting of secondary dendritic armsBending and shearing of secondary denritic armsBending and root melting of secondary armsFragments of primary dendrites grow into globular grains under forced convection


April 30, 2009Semi-solid Metal processing by Dr. Muhammad Kamran*Partial melting and Iso-thermal holdingLow temperature eutectic phase melts in semi-solid rangeHighly stressed grain boundaries favours wetting of grains with liquidGrain become globular to reduce curvature and liquid-solid interface energy

Evolution to Non-dendritic Microstructure


April 30, 2009Semi-solid Metal processing by Dr. Muhammad Kamran*Characteristics of SlurrySheared semi-solid slurry shows apparent viscosity similar to machine oil

SSM Processing exploits Solidification mechanism in the solid-liquid range i.e. nucleation and growth mechanisms

Introduction


April 30, 2009Semi-solid Metal processing by Dr. Muhammad Kamran*Alloy CharacteristicsSolidification rangeLow melting point phase/eutectic phaseTemperature Sensitivity of solid fractionCastabilityPotential for aging etc.


April 30, 2009Semi-solid Metal processing by Dr. Muhammad Kamran*Classification suggested by Flemings et.Al.RheocastingShearing the liquid while cooling from liquid to liquid solid range and casting a net-shape productThixocastingShearing a partially melted suitable precursor in semi-solid rangeCompocastingShearing a miscible or immiscible mixture of composite in the solid-liquid rangeIntroduction


April 30, 2009Semi-solid Metal processing by Dr. Muhammad Kamran*Other Mechanisms

Grain refinementSpray forming and sinteringUltrasonic vibrations etc.Evolution to Non-dendritic Microstructure


April 30, 2009Semi-solid Metal processing by Dr. Muhammad Kamran*Processing TechniquesTechniques for feed stockTechniques for Finished Product


April 30, 2009Semi-solid Metal processing by Dr. Muhammad Kamran*Semi-solid Metal Processing TechniquesTechniques for non-dendritic Feedstock

Mechanical StirringMegnatohydrodynamic (MHD) StirringStress Induced and melt Activated (SIMA) ProcessSpray FormingLiquidus CastingUltrasonic treatmentGrain refienment etc.


April 30, 2009Semi-solid Metal processing by Dr. Muhammad Kamran*Mechanical StirringDeveloped at MITStirring of liquid alloy while controlled cooling in the semi-solid range using auger, impeller or paddleBatch type or continuous processFor Rheocasting and Thixocasting Semi-solid Metal Processing Techniques


April 30, 2009Semi-solid Metal processing by Dr. Muhammad Kamran*Magnetohydrodynamic (MHD) Stirring

Patented by Alumax Inc.Vigorous stirring by rotating magnetic field within the mouldNormally for producing feedstock for thixocastingDisintegrated fine dendrites which convert to globular grains on partial meltingMost widely used process

Semi-solid Metal Processing Techniques


April 30, 2009Semi-solid Metal processing by Dr. Muhammad Kamran*Stress Induced and Melt Activated (SIMA) ProcessSevere deformation of precursor results in residual stressesOn heating recrystallisation occursOn partial melting low melting point phase becomes liquidHigh residual stress favours wetting of grain boundariesHigher curvature and liquid-solid interface energy favours globular grain morphology

Longer holding time favours coarsening and agglomeration which deteriorate semi-solidprocessability



April 30, 2009Semi-solid Metal processing by Dr. Muhammad Kamran*Liquidus CastingPouring of melt at near-liqudus temperatureHigher rate of Nucleation favouring fine grain sizeOn partial melting fine grains transform to globular grains

Grain RefinementPromote heterogeneous nucleation Finer grain sizeGrains transform to globular on partial melting



April 30, 2009Semi-solid Metal processing by Dr. Muhammad Kamran*Techniques for Net-shape ProductRheocastingThixoformingThixomouldingRheomoulding etc.Semi-solid Metal Processing Techniques


April 30, 2009Semi-solid Metal processing by Dr. Muhammad Kamran*RheocastingNon-dendritic ally slurry obtained from shearing while cooling from liquid state

Mechanical stirringMHD StirringNew Rheocasting (NRC)



April 30, 2009Semi-solid Metal processing by Dr. Muhammad Kamran*ThixocastingPartial melting of suitable feedstock

Mechanical stirringMHD stirringSIMA processSpray forming

ThixocastingThixoforgingSemi-solid Metal Processing Techniques


April 30, 2009Semi-solid Metal processing by Dr. Muhammad Kamran*ThixomouldingSimultaneous heating and shearing of solid feedstock in a chamber by rotating barrelDesigned for Mg alloyControlled atmosphereSimilar to injection mouldingSemi-solid Metal Processing Techniques


April 30, 2009Semi-solid Metal processing by Dr. Muhammad Kamran*RheomouldingVigorous Shearing of liquid alloy using screw type drive while coolingSimilar to Injection mouldingSuitable even for immiscible alloy formation and processing

Twin Screw Rheomoulding (TSRM) process is an upgradation



April 30, 2009Semi-solid Metal processing by Dr. Muhammad Kamran*Commercial featuresAdvantagesEnergy efficientProduction rate compete that for pressure die castingSmooth die filling with no air entrapment favouring product soundnessLower processing temperatureLower Impact to the dieReduced solidification shrinkage


April 30, 2009Semi-solid Metal processing by Dr. Muhammad Kamran*DisadvantagesRelatively higher feedstock material costPrecise control of operating condition is required.Liquid segregation may occur as a result of non-uniform heatingCommercial features


April 30, 2009Semi-solid Metal processing by Dr. Muhammad Kamran*Potential ApplicationsReplacement of permanent mould parts to eliminate machining and finishingPressure tight parts such as master brake cylinders, fuel rails, air conditioner compressor housing etc.High strength parts such as engine mounts, tie rods etc.Wear resistant parts made from hypereutectic alloys such as compressor piston, brake drums, gear shift levers etc.Forged parts requiring excessive toolingCommercial features


April 30, 2009Semi-solid Metal processing by Dr. Muhammad Kamran*Current Applications/Products

Hydraulic Brake ValveAutomobile WheelsBrake master CylinderCommercial features


April 30, 2009Semi-solid Metal processing by Dr. Muhammad Kamran*Door Pillars for AudiControl arms for SteeringFiat Engine bracketCommercial features


April 30, 2009Semi-solid Metal processing by Dr. Muhammad Kamran*Future DevelopmentsProcess developmentMechanism of formation of non-dendritic structureAlloy developmentSimulation studies of processViable process for steel and Cast Iron


April 30, 2009Semi-solid Metal processing by Dr. Muhammad Kamran*

Thank You for Your Patience


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