Microstructure and Mechanical Properties of an Extruded 6005A Al Alloy Composite Reinforced with TiC Nanosized Particles and Strengthened by Precipitation Hardening

Abstract

High-energy ball milling was carried out to disperse 3 vol% TiC nanoparticles (ex situ reinforcement) in a high-pressure inert gas-atomised prealloyed micron-sized 6005A Al alloy (AA6005A), with a Si/Mg atomic ratio of 1.32 powder matrix. Nanocomposite powders were consolidated by hot extrusion in strip shape at 500 °C, followed by a T6 ageing heat treatment. The microstructural features of the consolidated and precipitation hardening nanocomposites specimens were studied using X-ray diffractometry (DRX), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and electron backscatter diffraction (EBSD). The consolidated nanocomposites consisted of approximately equiaxed grains of different grain sizes with a high fraction of high-angle grain boundaries with average misorientation angles of approximately 35°. The nanocomposites showed remarkably higher hardness, Young’s modulus, yield, and ultimate strengths at room temperature than the extruded profiles of unreinforced milled AA6005A powders obtained through refinement of the Al alloy grain structure and a strong particle–matrix bonding, although with a drop in their ductility. The consolidated nanocomposite showed a weak response to industrial ageing heat treatment, as demonstrated by microstructural analyses and mechanical tests.

Keywords

• aluminium alloys
• nanocomposites
• microstructure
• mechanical properties
• extrusion
• ageing heat treatment