Evaluating extrudability of particle-reinforced 2124-Al MMCs and MMNCs within the warm working temperature range (170-280°C)

Abstract

This work evaluates the warm temperature extrudability of 2124-Al alloy metal matrix composites (MMCs) and metal matrix nano composites (MMNCs) produced by powder metallurgy. Green and sintered compacts were produced by mixing and blending 2124-Al alloy powder with 5 and 10 vol. % Al2O3 or 10 and 15 vol. % SiC powders in a high energy ball mill, followed by ambient temperature compaction and sintering at 490°C for 1 hr. An extrusion die was designed to reduce the diameter of the compacts by 30% from 8 mm to approximately 5.6 mm, and the die set was manufactured from H13 hot work tool steel. The die and samples were heated and soaked for 20 minutes, using a high temperature furnace, before extrusion in an Instron® press. Extrusion parameters, such as temperature and speed, were informed by uniaxial compression tests performed on a Gleeble 3500® together with results from Abaqus finite element modelling. The extrusion temperature was 280°C and the speed was 7 mms-1. Extrudability of the unreinforced 2124-Al was good, while the 5 vol. % Al2O3 reinforced MMNC and both SiC reinforced MMCs had poorer warm temperature extrudability. The composites were more difficult to extrude than the unreinforced alloy because they have higher resistance to deformation due to the hard and stiff reinforcing particles which do not deform easily. Also, this was attributed to a lack of lubrication during extrusion, which could have increased the friction and resistance to deformation, reducing material flow. Based on microstructural analysis, extrusion showed potential to improve distribution of SiC particles in 2124-Al grains. However, it seems that more deformation is required.