Effect of strontium modification on near- threshold fatigue crack growth in an Al-Si-Cu die cast alloy

Schaefer, M.; Fournelle, R.A.

doi:10.1007/bf02649866

Cited by 16 publications

(4 citation statements)

References 10 publications

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“…In modified alloys with much higher silicon particle concentrations, Δ K eff, th is consistently larger (as high as 4.0 MPa m 1/2 ) 16 ,. 17 The increase is due to the fact that cracks propagating with a maximum applied stress intensity factor below the transition stress intensity value proposed here ( K trmax = 7.0 MPa m 1/2 ), are slowed by growth through eutectic regions as the forward crack tip driving force is not large enough to damage the silicon particles. Consequently, an alloy with a higher percentage of silicon particles will present a more torturous route for cracks propagating with a maximum stress intensity below K trmax = 7.0 MPa m 1/2 .…”

Section: Discussionmentioning

confidence: 69%

“…This knowledge is required because fracture mechanics approaches may underestimate fatigue lives as initial defect sizes reach the length scale of other microstructural features that are distributed throughout the material. In an initial effort to understand fatigue crack growth mechanisms in cast Al–Si alloys, several studies have shown that the growth rate of long cracks is dependent on the silicon particle morphology in an average sense 14 –17 . The silicon particle morphology can be modified from a coarse lamellar structure to one containing well‐dispersed and spherodized particles by alloying with trace amounts of strontium or sodium, or subjecting the casting to extended solutionizing heat treatments.…”

Section: Introductionmentioning

confidence: 99%

“…The silicon particle morphology can be modified from a coarse lamellar structure to one containing well‐dispersed and spherodized particles by alloying with trace amounts of strontium or sodium, or subjecting the casting to extended solutionizing heat treatments. Cast Al–Si alloys with modified silicon particles generally exhibit a better resistance to long fatigue crack growth compared to unmodified alloys 14 –17 …”

Section: Introductionmentioning

confidence: 99%

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The influence of modified intermetallics and Si particles on fatigue crack paths in a cast A356 Al alloy

Gall

Yang

Horstemeyer

et al. 2000

Fatigue Fract Eng Mat Struct

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Mechanical fatigue tests were conducted on uniaxial specimens machined from a cast A356‐T6 aluminium alloy plate at total strain amplitudes ranging from 0.1 to 0.8% (R = − 1). The cast alloy contains strontium‐modified silicon particles (vol. fract. ~6%) within an Al–Si eutectic, dispersed α intermetallic particles, Al15 (Fe,Mn)3 Si2 (vol. fract. ~1%), and an extremely low overall volume fraction of porosity (0.01%). During the initial stages of the fatigue process, we observed that a small semicircular fatigue crack propagated almost exclusively through the Al–1% Si dendrite cells. The small crack avoided the modified silicon particles in the Al–Si eutectic and only propagated along the α intermetallics if they were directly in line with the crack plane. These growth characteristics were observed up to a maximum stress intensity factor of ~K trmax = 7.0 MPa m1/2 (maximum plastic zone size of 96 μm). When the fatigue crack propagated with a maximum crack tip driving force above 7.0 MPa m1/2 the larger fatigue crack tip process zone fractured an increased number of silicon particles and α intermetallics ahead of the crack tip, and the crack subsequently propagated preferentially through the damaged regions. As the crack tip driving force further increased, the area fraction of damaged α intermetallics and silicon particles on the fatigue fracture surfaces also increased. The final stage of failure (fast fracture) was observed to occur almost exclusively through the Al–Si eutectic regions and the α intermetallics.

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Section: Discussionmentioning

confidence: 69%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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The influence of modified intermetallics and Si particles on fatigue crack paths in a cast A356 Al alloy

Gall

Yang

Horstemeyer

et al. 2000

Fatigue Fract Eng Mat Struct

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“…Several authors 1–5 have concentrated on fatigue crack growth (FCG) studies of different aluminium alloys. Various microstructural features such as Si morphology, secondary dendrite arm spacing (DAS) as well as heat treatment, porosity level, testing conditions, operating atmospheres, operating temperature, etc.…”

Section: Introductionmentioning

confidence: 99%

Fatigue crack propagation behaviour of Al-Zn-Ce alloys

Govindaraju¹,

Jayaraju²,

Rao³

2011

Fatigue &Amp; Fracture of Engineering Materials &Amp; Structures

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A B S T R A C T This paper presents the investigation on fatigue crack growth behaviour of Al-Zn andAl-Zn-Ce alloys. Fatigue tests were carried out on as-cast and heat-treated CT specimens according to ASTM E647 testing standard. The test results showed that the addition of rare earth element (cerium) and heat treatments (T6 and T5) had very strong influence on fatigue strength. This enhancement was due to metallurgical changes in the alloy system. Cerium eliminates the porosities and refines microstructures of the alloy, showing the improved fatigue crack growth behaviour. In addition, the fatigue fractured specimens were examined using a scanning electron microscope to clarify the fracture initiation points.cycles for crack initiation N f = number of cycles at specimen failure R = load ratio (P min /P max ) W = specimen width (mm) σ u = ultimate strength (MPa) K = stress intensity (MPa √ m) K th = threshold stress intensity (MPa √ m) CT = compact tension specimen HIP = hot isostatic process RHN = Rockwell hardness number SDAS = secondary dendritic arm spacing (μm) I N T R O D U C T I O NFatigue is an important parameter to be considered in the behaviour of mechanical components subjected to constant and variable amplitude loading. Mechanical, metallurgical and environmental variables can influence the fatigue resistance of a structural component. Fatigue is a primary cause of all engineering failure. The increased use of cast aluminium alloys in automotive applications creates the need for a deeper understanding of fatigue performance and the influence of processing parameters. The method of assessing the fatigue properties resulting from Correspondence: H. K. Govindaraju. E-mail: anchith_g_raj@yahoo.co.in different processing conditions require establishment of extensive database of rate of crack growth versus stress intensity (da/dN -K) information.Several authors 1-5 have concentrated on fatigue crack growth (FCG) studies of different aluminium alloys. Various microstructural features such as Si morphology, secondary dendrite arm spacing (DAS) as well as heat treatment, porosity level, testing conditions, operating atmospheres, operating temperature, etc. have been investigated. Si morphology influences on FCG of aluminium alloy, die cast alloys, Al -12% Si -0.35% Mg and rheocast alloys have been reported. Secondary dendritic arm spacing was observed to play an important role in the fatigue behaviour for different heat treating conditions of

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Fatigue crack growth and wear behaviors in rheocast Al−Si−Mg alloys

2003

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Rheocast aluminum alloys, which consist of globular α-Al cells, refined grains and eutectic Si particles, were used to investigate fatigue crack growth and wear characteristics. The Si particles were systematically varied from coarse and acicular shapes to small and globular ones. At low ΔK, fatigue crack growth rates decreased in samples consisting of acicular Si particles of large grain size, which induced a large amount of crack closure. Large and acicular Si particles were easily cracked and separated the particle/matrix interface, which promoted to fracture at smaller ΔK. On the other hand, small Si particles made fatigue crack grow, even at a high ΔK region, and increased the fracture toughness of the alloy. However, in the wear test, small eutectic Si particles were pulled out by friction force during sliding wear and the wear loss amount increased with increase in sliding distance.

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Effect of strontium modification on near- threshold fatigue crack growth in an Al-Si-Cu die cast alloy

Cited by 16 publications

References 10 publications

The influence of modified intermetallics and Si particles on fatigue crack paths in a cast A356 Al alloy

The influence of modified intermetallics and Si particles on fatigue crack paths in a cast A356 Al alloy

Fatigue crack propagation behaviour of Al-Zn-Ce alloys

Fatigue crack growth and wear behaviors in rheocast Al−Si−Mg alloys

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