Microstructure and Composition of Alumina/Aluminum Composites Made by Directed Oxidation of Aluminum

Breval, E.; Aghajanian, M. K.; Luszcz, S. J.

doi:10.1111/j.1151-2916.1990.tb06735.x

Cited by 66 publications

(17 citation statements)

References 5 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Directed metal oxidation of aluminum and other liquid-solid displacement reactions all exhibit linear growth behavior. [17][18][19][20][21][22][23][24][25][26] Indeed, the microstructure of RMP composites is consistent with this linear behavior. Even in the relatively early stages of the reaction between aluminum and mullite, channels that are ∼1 m wide develop near the reaction interface in RMP composites.…”

Section: Discussionsupporting

confidence: 78%

Kinetics of Ceramic‐Metal Composite Formation by Reactive Metal Penetration

Fahrenholtz

Ewsuk

Loehman

et al. 1998

Journal of the American Ceramic Society

View full text Add to dashboard Cite

The rate of composite formation via reactive metal penetration has been determined. The metal penetration depth (i.e., the reaction-layer thickness) was measured from cross sections of partially reacted samples. Samples were fabricated by immersing dense mullite preforms in a bath of molten aluminum at temperatures of 900°-1300°C and reacting the combination for up to 250 min. In general, the reactionlayer thickness increased linearly as the time increased. Penetration rates as high as 6.0 mm/h were measured; however, the aluminum penetration rate varied dramatically with time and temperature. The penetration rate increased when the reaction temperature was increased from 900°C to 1100°C, and the reaction-layer thickness increased linearly as the time increased in this temperature range. At temperatures of 1150°C and above, reaction-layer formation slowed or stopped after a relatively short period of rapid linear growth, because of an increase in silicon concentration near the reaction interface. The duration of the rapid linear growth period decreased from 25 min at 1150°C to <1 min at 1250°C. At temperatures of 1300°C and above, no reaction layer was detected by using optical microscopy. Kinetics data and transmission electron microscopy analysis suggest that the reaction was inhibited at higher reaction temperatures and longer times, because of silicon buildup and saturation at the reaction front. Calculations show that, as the reaction temperature increased, the silicon production increased faster than the silicon transport. The two rates were approximately equal at a temperature of 1100°C.

show abstract

Section: Discussionsupporting

confidence: 78%

Kinetics of Ceramic‐Metal Composite Formation by Reactive Metal Penetration

Fahrenholtz

Ewsuk

Loehman

et al. 1998

Journal of the American Ceramic Society

View full text Add to dashboard Cite

show abstract

“…Reaction [8] is observed at bonding interfaces in metal matrix composites [38][39][40][41][42][43] and in studies of the oxidation behavior of Al-Mg alloys. Reaction [8] is observed at bonding interfaces in metal matrix composites [38][39][40][41][42][43] and in studies of the oxidation behavior of Al-Mg alloys.…”

Section: Discussionmentioning

confidence: 99%

Surface oxide and the role of magnesium during the sintering of aluminum

Lumley

Sercombe

Schaffer

1999

Metall Mater Trans A

196

View full text Add to dashboard Cite

The effect of trace additions of magnesium on the sintering of aluminum and its alloys is examined. Magnesium, especially at low concentrations, has a disproportionate effect on sintering because it disrupts the passivating Al 2 O 3 layer through the formation of a spinel phase. Magnesium penetrates the sintering compact by solid-state diffusion, and the oxide is reduced at the metal-oxide interface. This facilitates solid-state sintering, as well as wetting of the underlying metal by sintering liquids, when these are present. The optimum magnesium concentration is approximately 0.1 to 1.0 wt pct, but this is dependent on the volume of oxide and, hence, the particle size, as well as the sintering conditions. Small particle-size fractions require proportionally more magnesium than large-size fractions do.

show abstract

“…As was previously seen in the cross‐sectional images of this specimen, the residual filler metal layer is discontinuous. That is, the joint contains a dispersion of metallic aluminum within an alumina matrix, similar to the microstructure of alumina–matrix composites formed by the DIMOX process 16,24,25 …”

Section: Resultsmentioning

confidence: 96%

Effects of Brazing Time and Temperature on the Microstructure and Mechanical Properties of Aluminum Air Brazed Joints

Kim

Weil

2007

Journal of the American Ceramic Society

View full text Add to dashboard Cite

High‐purity aluminum foil was used to join alumina substrates directly in air at temperatures ranging from 800° to 1200°C and soak times of 1–100 h. It was found that the bend strengths of the resulting Al2O3/Al/Al2O3 joints generally increase with increasing brazing temperature and time, with a maximum bend strength of 135 MPa on average achieved in samples joined at 1200°C for 100 h. Additionally it was determined that measurable ductility is retained in the joint even after exposure under extended high‐temperature conditions. During joining, an Al2O3 scale forms along the interface between the aluminum and adjacent substrates. An increase in brazing temperature and/or time leads to intergrowth and sintering between this thermally grown oxide layer and the substrate surface, which appears to be the primary source of improved joint strength. Fracture analysis indicates that the Al2O3/Al/Al2O3 joints generally fail via one of three mechanisms, (1) by de‐bonding along the foil/substrate interface in specimens that were joined at low temperature or held at temperature for an insufficient period of time; (2) by ductile rupture in specimens that were joined at conditions that promoted sintering between the oxidized foil and adjacent alumina faying surfaces, but left behind a continuous residual aluminum layer within the joint; or (3) by mixed‐mode fracture in specimens joined at high temperature and long exposure times, in which the thermally grown alumina that forms between the two substrates is interrupted by dispersed pockets of residual aluminum metal.

show abstract

Microstructure and Composition of Alumina/Aluminum Composites Made by Directed Oxidation of Aluminum

Cited by 66 publications

References 5 publications

Kinetics of Ceramic‐Metal Composite Formation by Reactive Metal Penetration

Kinetics of Ceramic‐Metal Composite Formation by Reactive Metal Penetration

Surface oxide and the role of magnesium during the sintering of aluminum

Effects of Brazing Time and Temperature on the Microstructure and Mechanical Properties of Aluminum Air Brazed Joints

Contact Info

Product

Resources

About