Effect of alternative heat-treatment parameters on the aging behavior of short-fiber-reinforced 2124 Al composites

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The 2124 Al alloy and a composite of the 2124 Al alloy reinforced with 20 % of volume fractions of d-Al2O3 short fibers made by squeeze casting were subjected to controlled and systematic aging treatments.The materials were solution treated at (495, 525 and 555) °C.After quenching, the matrix alloy and the composite were artificially aged at (160, 170, 180 and 190) °C up to 36 h.The aging was monitored with hardness measurements and differential scanning calorimetry.The time required to reach the peak hardness of the composite matrix during a precipitation treatment was shorter than that for the unreinforced 2124 Al.An increase in the solution-treatment temperature resulted in an increase of the composite-matrix hardness.The d-Al2O3-reinforced composite exhibits no grain-boundary melting, but appears to show incipient melting around short alumina fiber interfaces at temperatures above 525 °C.The highest HV value was obtained after solutionizing at 495 °C for 6 h, followed by water quenching and aging at 190 °C for 10 h for the unreinforced matrix alloy.In the case of the reinforced alloy the highest HV value was found after solutionizing at 555 °C for 6 h, quenching and aging at 170 °C for 12 h.Keywords: aluminum matrix composite,