Effect of SiC‐Reinforcement and Equal‐Channel Angular Pressing on Microstructure and Mechanical Properties of AA2017

Abstract

This article deals with powder metallurgical production and modification of properties of a composite material based on an age‐hardenable Al–Cu alloy. The main objective is to improve the mechanical properties by particle reinforcement and equal‐channel angular pressing (ECAP). Our approach makes use of four hardening mechanisms: precipitation hardening, particle reinforcement, strain‐hardening, and grain boundary hardening associated with an ultrafine‐grained microstructure produced by ECAP. The main processing steps are high‐energy ball milling, hot‐isostatic pressing, extrusion, heat treatment, and a single ECAP pass. Microstructures are analyzed by optical microscopy, scanning electron microscopy, and scanning transmission electron microscopy. The mechanical properties are characterized by hardness measurements and quasi‐static tensile testing. Our experimental results show that the proposed processing route results in a nearly homogeneous distribution of SiC particles in the matrix. The combination of particle reinforcement and ECAP leads to an improvement of ultimate tensile strength by almost 300 MPa compared to the unreinforced alloy. A subsequent heat treatment leads to a further increase in hardness and strength that can be related to changes in the defect structure. Our study provides detailed information on how processing steps, microstructures, and mechanical behavior are interrelated in this technologically relevant class of materials.

Influence of Boron on the Creep Behavior and the Microstructure of Particle Reinforced Aluminum Matrix Composites

“…The results on room temperature properties are published in [1][2][3][4][5][6]. In addition, creep tests were carried out, in which all tested AMCs showed higher creep rates than the unreinforced reference material.…”

Influence of Particulate Reinforcement and Equal-Channel Angular Pressing on Fatigue Crack Growth of an Aluminum Alloy

“…Al2O3 powder with a particle size fraction of 0.2-2 µm was used as reinforcing component. The composite powder, consisting of 95 vol % matrix material and 5 vol % Al2O3 particles, was processed in a high-energy ball mill and hot-degassed at 450 °C and 0.06 bar for 4 h. Afterwards, compaction was performed by hot isostatic pressing at 450 °C and 1100 bar for 3 h. The manufacturing process is described in more detail in [28]. The non-ECAP-processed conditions, unreinforced, and reinforced, were solid-solution treated at 505 °C for 60 min, water-quenched, and subsequently naturally aged at room temperature for one month in order to adjust an underaged condition.…”

“…The non-ECAP-processed conditions, unreinforced, and reinforced, were solid-solution treated at 505 °C for 60 min, water-quenched, and subsequently naturally aged at room temperature for one month in order to adjust an underaged condition. For the ECAP-processed conditions, as described in [28], a pre-ECAP aging at 140 °C was carried out for 10 min to increase the workability. Immediately after the pre-ECAP aging, the material was ECAP-processed at 140 °C for one pass.…”

“…This shows, that the effect of strain hardening during ECAP is less pronounced than in the unreinforced material. Both reinforced conditions exhibit minor ductility, which is ascribed to the particles which act as interior notches [28].…”

“…It is well-known that small particles cause significantly higher strain hardening and that they are less susceptible to cracking as compared to coarser particles [26,27]. As matrix material, the Al 2017 alloy has been chosen here and in preliminary studies [28], because it combines attractive properties, such as good fracture toughness in the underaged condition, high resistance against crack propagation, and excellent high-temperature strength, which enables future applications for lightweight structures, e.g., for the aerospace and aeronautical industries.…”