Effect of production route and heat treatment on the microstructure and mechanical properties of AA2124/vol%25MoSi2 composites

In the present work, AA2124/25vol%MoSi2 composites were produced by two different powder metallurgy routs: high energy ball milling of the reinforcement and alloy powder and then consolidation by extrusion (B composite), and wet blending of the powders with cyclohexane and extrusion (W composite). The composite bars then were cut to small pieces ready for structural and mechanical characterization. Some of the samples were heat treated to T6 temper (solution treated and artificially aged to peak hardness). Hardness, micro hardness and compression tests performed on both as-extruded and heat-treated samples. The compression tests were performed under quasistatic loading (strain rate of 8×10-4) at room temperature. Microstructure and fracture profile were observed by scanning electron microscopy (SEM). The forming reaction products at matrix were identified by energy-dispersive X-ray (EDX) and X-ray diffraction analysis. The results showed that in both cases, the copper rich interphase has been formed. Hardness increased substantially by addition of intermetallic compounds to 2124 matrix. Heat treatment improved the mechanical properties of both composites. The composite produced by high energy method had higher yield strength and lower elongation to failure comparing to wet blended composite. Study the fracture surface features by SEM verified that the lower elongation of B composite is due to work hardening of the matrix during the milling and/or dynamic recrystallization of the matrix during extrusion. Particle debonding was also more sensible in W composite.

کلیدواژه ها:

2124 aluminium composites ، Molybdenum disilicide ، Heat treatment ، Microstructure ، Mechanical properties