Showing papers on "Metal matrix composite published in 1974"

Reinforced metal matrix composite

Abstract: A carbon fiber reinforced metal matrix composite is produced by depositing a metal boride coating on the surface of the fibers and subsequently immersing the fibers in a molten bath of the metal matrix material. The boride coating is formed by passing carbon fiber through a gaseous mixture of chlorides of the metal and boron in the presence of zinc vapor at elevated temperatures. The subsequent reaction deposits out a submicron lamina of metal boride on the carbon fibers serving to enhance wetting of the fibers by the molten metal, with the lamina preventing chemical reaction between the fibers and metal matrix materials and also providing a strong mechanical bond therebetween.

Production of graphite fiber reinforced metal matrix composites

Abstract: A graphite fiber reinforced metal matrix composite prepared by hot-pressing, comprising layers of a matrix metal selected from the group consisting of magnesium and magnesium based alloys; in combination with alternate layers of a graphite fiber. The improvement consists of small additions of a metal selected from the group consisting of titanium, chromium, nickel, zirconium, hafnium and silicon in order to promote wetting and bonding between the graphite fibers and the matrix metal.

The tensile failure modes of metal-matrix composite materials

Abstract: The strengths of individual boron fibers extracted from various as-received and thermally fatigued aluminum alloy matrix materials were measured. The results are described in terms of a Weibull distribution, and strengths of composites fabricated from these fibers are calculated in terms of lower and upper bounds. Tests conducted on composite specimens indicated that strengths approaching the upper bounds can be achieved in composites fabricated by normal diffusion bonding techniques. Cyclic temperature changes effectively reduced the strength values toward the lower bounds. It was concluded that this effect resulted from the degradation of the strength of the fiber-matrix bond.

Metal matrix composite fabrication by liquid infiltration

Abstract: A pressure-vacuum liquid infiltration process for fabricating metal- matrix composite materials was developed. The process was used to fabricate flat tensile bars and hoop-test rings of both magnesium/boron and aluminum/boron. The effects of processing parameters, matrix alloying, and boron surface coating on the tensile properties were evaluated. A matrix effectiveness factor of 1.1 was determined from magnesium/boron tensile data. Although protective coatings of both silicon carbide and boron nitride were used, all aluminum/boron composites evaluated exhibited matrix effectiveness factors less than unity, indicnting that excessive filament degradation had occurred. (5 figures, 5 tables) (auth)

A study of the diffusional behavior of a two-phase metal matrix composite exposed to a high temperature environment

Abstract: The progress of diffusion-controlled filament-matrix interaction in a metal matrix composite where the filaments and matrix comprise a two-phase binary alloy system was studied by mathematically modeling compositional changes resulting from prolonged elevated temperature exposure. The analysis treats a finite, diffusion-controlled, two-phase moving-interface problem by means of a variable-grid finite-difference technique. The Ni-W system was selected as an example system. Modeling was carried out for the 1000 to 1200 C temperature range for unidirectional composites containing from 6 to 40 volume percent tungsten filaments in a Ni matrix. The results are displayed to show both the change in filament diameter and matrix composition as a function of exposure time. Compositional profiles produced between first and second nearest neighbor filaments were calculated by superposition of finite-difference solutions of the diffusion equations.