CAR process: A technique for significant enhancement of as-cast MMC properties

Continual annealing and roll-bonding (CAR) process was used in this study as a very effective method for improving the microstructure and mechanical properties of the A356/SiC metal matrix composite produced by semi-solid metal processing. The results showed that the increase in the number of cycles led to the following points: (a) the uniformity of the silicon and silicon carbide in the aluminum matrix was improved, (b) the Si particles became finer and more spheroidal in appearance, (c) the porosity was decreased, (d) the bonding quality between the reinforcement (SiC particles) and the matrix (A356 aluminum) was improved, (e) the particle free zone disappeared, and therefore (f) the tensile strength, elongation, and formability index of the samples were improved. The microstructure of the manufactured A356/SiC composite after ten cycles indicated a totally modified structure so that its tensile strength, elongation, and formability index values reached 166.7 MPa, 23.9%, and 3984 MPa·% which were 1.74, 4.19, and 7.29 times greater than those of the as-cast composite, respectively.

Research Highlights
► The microstructure of MMC after tenth CAR cycle showed totally modified structure.
► The tensile strength of the samples improved when the number of cycles increased.
► When the number of cycles was raised, the elongation value improved.
► By increasing the number of CAR cycles, the formability index improved.