The correlation of microstructure and mechanical properties of in-situ Al-Mg2Si cast composite processed by equal channel angular pressing

In this paper, the effect of equal channel angular pressing (ECAP) on microstructure and mechanical properties of hypereutectic Al-20%Mg2Si and Al-15%Mg2Si, as well as hypoeutectic Al-10%Mg2Si composites has been investigated. After fabricating the composites by in-situ casting, the composites were processed using the ECAP process up to two passes at room temperature. Microstructural studies have been carried out using a field emission scanning electron microscopy equipped with an energy dispersive X-ray spectrometer. Mechanical properties were also documented using Vickers microhardness and shear punch tests. In the hypereutectic composites, a decrease in the average size of pro-eutectic Mg2Si (Mg2Sip) particles, breakages in eutectic networks, and lengthening of the Al (α) phase in direction of shear bands were observed after the ECAP process. For instance, the average size of Mg2Sip Particles in Al-20%Mg2Si composite reduced from 40 to 17 μm after 2 passes of ECAP. Furthermore, a uniform distribution of Mg2Sip particles was developed in the matrix. In hypoeutectic composite, the ECAP process caused a uniform distribution of eutectic Mg2Si (Mg2SiE) in the matrix that considered a favorable microstructure. Microhardness measurements and shear punch results showed an ascending trend after each pass of ECAP for all specimens. For example, microhardness and shear strength of Al-20%Mg2Si increased from 88 HV and 109 MPa to 119 HV and 249 MPa after two passes indicating 35% and 34% increments, respectively. Density and porosity calculations by Archimedes principle revealed that the density of the composites increased after two passes of ECAP due to the reduction of porosity

alloy

Microstructural evolution to ultrafine grains and consequently, enhancement of mechanical properties has been recently considered for tube formed specimens using various severe plastic deformation methods. In this research, Al-Zn-Mg-Cu tube was processed by the famous equal channel angular extrusion process using a polyurethane mandrel up to two passes at room temperature. Although strength and hardness of the aluminum tube are increased dramatically after the first pass, the aforementioned parameters are enhanced slightly during the second pass of the process. In addition, tube hardness uniformity is decreased remarkably by applying for the first pass and it is improved after the second pass. According to parameters of work-hardening behavior and formability, the flow stress rate of the aluminum tube is reduced by increasing the ECAE pass number. Microstructural analyses showed that low angle and straight grain boundaries of initial sample are transformed into the high angle wavy grain boundaries after introducing the second pass of the process

on the improvement of mechanical and tribological response

This work deals mechanical and tribological properties of pure copper, reinforced by various weight percentages of tin, before and after the application of equal channel angular pressing. It is found that the hardness, yield, and ultimate shear strengths are considerably improved through ECAP due to grain refinement. The effect of ECAP process on mechanical properties of dilute copper alloys is more significant than that of the pure condition. Also, the strengthening behavior is slightly intensified by increasing the amount of tin content in pure copper. Additionally, work-hardening potential of CP-Cu is restricted due to the ECAP process and also, through the production of dilute copper alloys. The results showed that the effect of ECAP on friction coefficient reduction is more sizeable than making the dilute alloys. Furthermore, the reduction of electrical conductivity in the deformed materials relies on the lattice distortion increase of copper due to the addition of Sn to Cu and the increment of dislocations density. Finally, ECAP procedure and alloying together, terminate to the better wear response of the materials.C1 [Ebrahimi, M.] Univ Maragheh, Fac Engn, Dept Mech Engn, POB 55136-533, Maragheh, Iran.[Shaeri, M. H.; Armoon, H.] IKIU, Dept Mat Sci & Engn, Qazvin, Iran.[Gode, C.] Pamukkale Univ, Program Machine, Sch Denizli Vocat Technol, Denizli, Turkey.[Shamsborhan, M.] Islamic Azad Univ, Mahabad Branch, Dept Engn, Mahabad, Iran

Investigating microstructure and mechanical properties of aluminum matrix reinforced-graphene nanosheets composites fabricated by mechanical milling and equal channel angular pressing

A few layer graphene reinforced metal matrix nanocomposites with excellent mechanical properties and low density are a new class of advanced materials for a broad range of applications. A facile three steps approach based on ultra-sonication for dispersion of graphene nanosheets (GNSs), ball milling for Al powder mixing with different GNSs weight percent and equal channel angular pressing for powders consolidation at 200°C, has been applied for nanocomposites fabrication. The Raman analysis revealed that the GNSs in the sample with 0.25 wt.% were exfoliated by the creation of some defects and disordering. X-ray diffraction and microstructural analysis confirmed that the interaction of GNSs and matrix was almost mechanical interfacial bonding. Density test demonstrated that all samples except 1 wt.% GNSs were fully densified due to the formation of microvoids, which was observed in scanning electron microscope analysis. Investigation of mechanical properties showed that by using Al powders with commercial purity, 0.25 wt.% sample possessed the maximum hardness, ultimate shear strength and uniform normal displacement in comparison with other samples. Highest mechanical properties which was observed in 0.25 wt.% GNSs composite, resulting from the embedding of exfoliated GNSs between Al powders, excellent mechanical bonding and grain refinement. Oppositely, agglomerated GNSs and existence of microvoids caused deterioration of mechanical properties in 1 wt.% sample