Variable-density composite articles, preforms and methods
A metal matrix composite article that includes at least first and second regions, first and second reinforcement materials, a metal matrix composite material occupying the second region of the body and comprising a metal matrix material and the second reinforcement component, a preform positioned in the first region of the body and infiltrated by at least the metal matrix material of the metal matrix composite material. The article further includes a transition region located proximate an outer surface of the preform that includes a distribution of the second reinforcement component comprising a density increasing according to a second gradient in a direction toward the outer surface of the preform.
1. A metal matrix composite article, comprising:
a cast, reinforced body, the body comprising a first region and a second region, the first region having more reinforcement than the second region;
a first reinforcement component;
a second reinforcement component;
a metal matrix composite material occupying the second region of the body and comprising a metal matrix material and the second reinforcement component;
a preform positioned in the first region of the body and infiltrated by at least the metal matrix material of the metal matrix composite material, the preform comprising
a first end,
a second end,
an outer surface,
the first reinforcement component, the first reinforcement component comprising a density increasing between the first end of the preform and the second end of the preform according to a first gradient, and
a porous structure configured to allow passage of the metal matrix material into the preform and to block or reduce passage of the second reinforcement component into the preform; and
a transition region extending between the first and second region of the body and located proximate the outer surface of the preform, the transition region comprising a distribution of the second reinforcement component adjacent to the outer surface of the preform, the distribution of the second reinforcement component comprising a density increasing according to a second gradient in a direction toward the outer surface of the preform.
2. The metal matrix composite article of claim 1 , wherein the metal matrix material comprises a metal or a metal alloy and wherein the second reinforcement component comprises a ceramic particle component and/or a ceramic fiber component.
3. The metal matrix composite article of claim 2 , wherein the metal matrix material comprises aluminum, magnesium, or an alloy thereof.
4. The metal matrix composite article of claim 1 , wherein the first reinforcement component comprises a ceramic particle component and/or a ceramic fiber component.
5. The metal matrix composite article of claim 1 , wherein the transition region comprises a thickness corresponding to an amount of the metal matrix material infiltrated into the preform.
6. The metal matrix composite article of claim 1 , wherein the distribution of the second reinforcement component at the outer surface of the preform comprises a first volume fraction that matches a volume fraction of the first reinforcement component at the outer surface of the preform.
7. The metal matrix composite article of claim 6 , wherein the metal matrix composite material comprises the second reinforcement component at a minimum volume fraction, and wherein the volume fraction of the distribution of the second reinforcement component decreases linearly or substantially linearly from the first volume fraction to the minimum volume fraction.
8. The metal matrix composite article of claim 1 , wherein the article is a cast brake rotor.
9. The metal matrix composite article of claim 8 , wherein the first region comprises a friction face and the second region comprises a hub.
10. The metal matrix composite article of claim 8 , further comprising a second preform positioned in the first region of the body adjacent to the first preform, the second preform infiltrated by at least the metal matrix material of the metal matrix composite material.