Characterisation and modelling of defect formation in direct-chill cast AZ80 alloy

Mackie, David M.; Robson, James; Withers, Philip J.; Turski, Mark

doi:10.1016/j.matchar.2015.03.033

Cited by 19 publications

(13 citation statements)

References 21 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The presence of these large graphite particles in the immediate vicinity of the FCI forms the second portion of the justification for the observed failure location, as these brittle particles act as local stress concentrations within the poorly fused mateiral for which fatigue cracks will nucleate more easily. This agrees well with Mackie et al whom investigated the effect of oxide films on DC cast AZ80 Mg alloy and found them to have an embrittling effect, with approximatley half the ductility of the defect free material, which is largely similar to the influence of graphite particles which act to embrittle the material in the current study [35]. Further supporting these observations, the second FCI location displayed similar initiation morphology, also with large and numerous graphite particles in the vicinity of the crack nucleation location.…”

Section: Fracture Behaviour In Full-scale Component Under Representatsupporting

confidence: 93%

“…Furthermore, the authors are cognizant of the (a) (b) FCI stochastic nature of fatigue, however this observation is supported by the final fracture region being ~26% in the sample extracted from location #13, which agrees well with the degraded strength (and associated fatigue performance) observed in location #3 in the vicinity of the defect. Mackie et al observed a similar detrimental effect to the strength of direct-chill cast AZ80 Mg when comparing defect free material to those with high intermetallic particle density and entrained oxide films under monotonic loading [35].…”

Section: Fracture Behaviour In Laboratory Test-specimens Under Fully mentioning

confidence: 87%

See 1 more Smart Citation

Effect of thermomechanical processing defects on fatigue and fracture behaviour of forged magnesium

Gryguc

Behravesh

Jahed

et al. 2020

Frattura Ed Integrità Strutturale

View full text Add to dashboard Cite

The microstructural origins of premature fatigue failures were investigated on a variety of forged components manufactured from AZ80 and ZK60 magnesium, both at the test specimen level and the full-scale component level. Both stress and strain-controlled approaches were used to characterize the macroscopically defect-free forged material behaviour as well as with varying levels of defect intensities. The effect of thermomechanical processing defects due to forging of a industrially relevant full-scale component were characterized and quantified using a variety of techniques. The fracture initiation and early crack growth behaviour was deterministically traced back to a combination of various effects having both geometric and microstructural origins, including poor fusion during forging, entrainment of contaminants sub-surface, as well as other inhomogeneities in the thermomechanical processing history. At the test specimen level, the fracture behaviour under both stress and strain controlled uniaxial loading was characterized for forged AZ80 Mg and a structure-property relationship was developed. The fracture surface morphology was quantitatively assessed revealing key features which characterize the presence and severity of intrinsic forging defects. A significant degradation in fatigue performance was observed as a result of forging defects accelerating fracture initiation and early crack growth, up to 6 times reduction in life (relative to the defect free material) under constant amplitude fully reversed fatigue loading. At the full-scale component level, the fatigue and fracture behaviour under combined structural loading was also characterized for a number of ZK60 forged components with varying levels of intrinsic thermomechanical processing defects. A novel in-situ non-contact approach (utilizing Digital-Image Correlation) was used as a screening test to establish the presence of these intrinsic defects and reliably predict their effect on the final fracture behaviour in an accelerated manner compared to conventional methods.

show abstract

Section: Fracture Behaviour In Full-scale Component Under Representatsupporting

confidence: 93%

Section: Fracture Behaviour In Laboratory Test-specimens Under Fully mentioning

confidence: 87%

Effect of thermomechanical processing defects on fatigue and fracture behaviour of forged magnesium

Gryguc

Behravesh

Jahed

et al. 2020

Frattura Ed Integrità Strutturale

View full text Add to dashboard Cite

show abstract

“…8,9 In the direct chill (DC) casting of Mg-Al-based alloys, temperature fluctuations and reaction between the steel launder system and liquid alloy can create Al-Mn(-Fe) particles that can block filters and/or agglomerate into clusters that can become engulfed in the final ingot. 10 While there is a large body of industrial know-how on methods to control Al-Mn(-Fe) particle formation, there is limited scientific understanding on Fe pickup, and the nucleation, growth and settling of Al-Mn(-Fe) particles, and a deeper understanding is required to minimise the build-up of die-casting sludge and prevent large Al-Mn(-Fe) clusters from entering castings.…”

Section: Introductionmentioning

confidence: 99%

“…7, 2019 https://doi.org/10.1007/s11837-019-03471-2 clusters of large Al 8 Mn 5 intermetallic particles. 10 Since oxides and large brittle intermetallics are deleterious to tensile ductility and fatigue life, 10,11,15 it is important to understand how Al 8 Mn 5 particles cluster around entrained oxides. One aim of this work is to elucidate the IMC clustering mechanism on entrained oxides and provide new insights that could enable the prevention of these defects in DC cast ingots.…”

Section: Introductionmentioning

confidence: 99%

Al8Mn5 Particle Settling and Interactions with Oxide Films in Liquid AZ91 Magnesium Alloys

Peng

Zeng

et al. 2019

JOM

View full text Add to dashboard Cite

Al 8 Mn 5 particles form as primary solidification phases in Mg-Al-based alloys and are important for ensuring adequate corrosion resistance. However, excessive Al 8 Mn 5 formation above the a-Mg liquidus temperature can lead to sludge formation, and the clustering of Al 8 Mn 5 particles on oxide films can generate deleterious casting defects. Here, we use analytical SEM and realtime synchrotron x-ray radiography to study Al 8 Mn 5 particle settling, the formation of a sludge layer, and the mechanism of Al 8 Mn 5 clustering on oxides in AZ91 containing two Fe levels. It is shown that settling Al 8 Mn 5 can become trapped in entrained oxide and that new Al 8 Mn 5 particles also seem to nucleate on oxide films. On cooling, these Al 8 Mn 5 particles continue to grow, creating large Al 8 Mn 5 clusters.

show abstract

“…In their studies, the topics mainly focus on microstructure, hot tearing, and mechanical properties of round billets, which are the preferred raw materials used to produce various products such as rods, bars, tubes and wires by forge or extrusion. [4][5][6][7][8][9][10] However, very few works have been carried out about the elucidation of macrosegregation of DC casting of magne-sium alloy, especially for large sized at ingot of magnesium alloy intended to be eventually rolled into plate. Obviously, to roll magnesium sheet from at ingot instead of round billet can effectively improve the utilization rate of raw material.…”

Section: Introductionmentioning

confidence: 99%

Effect of Direct Chill Casting Process Parameters on the Microstructure and Macrosegregation of Mg-Al-Zn Ingot

et al. 2017

View full text Add to dashboard Cite

It has been demonstrated that the microstructure and macrosegregation of ingot produced by direct chill casting would take remarkable effect on its deformation behavior. In the present study, the in uence of casting speed and temperature on the microstructure and macrosegregation of AZ81 ingot prepared by a self-designed crystallizer (220 × 220 mm) was investigated. The results show that the volume fraction of β-Mg 17 Al 12 predicted by the Gulliver-Scheil model agrees well with image analysis results of the ingots prepared at different casting parameters. Moreover, the casting speed affects the macrosegregation greatly while it has slight in uence on the distribution of β-Mg 17 Al 12 , and the casting temperature has slight in uence on macrosegregation of ingot while it has strong in uence on the distribution of β-Mg 17 Al 12. The optimal casting speed and casting temperature for the AZ81 ingot are 80 mm/min and 953 K, respectively. The corresponding maximum values of ultimate tensile strength, yield strength and elongation are 265 MPa, 210 MPa and 3.5%, respectively.

show abstract

Characterisation and modelling of defect formation in direct-chill cast AZ80 alloy

Cited by 19 publications

References 21 publications

Effect of thermomechanical processing defects on fatigue and fracture behaviour of forged magnesium

Effect of thermomechanical processing defects on fatigue and fracture behaviour of forged magnesium

Al8Mn5 Particle Settling and Interactions with Oxide Films in Liquid AZ91 Magnesium Alloys

Effect of Direct Chill Casting Process Parameters on the Microstructure and Macrosegregation of Mg-Al-Zn Ingot

Contact Info

Product

Resources

About