Microstructure, and Mechanical and Wear Properties of Grp/AZ91 Magnesium Matrix Composites.

Chang-Rui Wang,Yan Bai,Kun-Kun Deng

doi:10.3390/ma12071190

Abstract

Based on semi-solid mixing technology, two kinds of as-cast Grp (Graphite particles)/AZ91 composites with different Grp volume fractions (5 vol %, 10 vol %) were prepared; these are called 5 vol % Grp/AZ91 composites and 10 vol % Grp/AZ91 composites, respectively. In order to eliminate casting defects, refine grains, and improve mechanical properties, thermal deformation analysis of these composites was conducted. The effect of the addition of Grp and thermal deformation on the microstructure, mechanical properties, and wear resistance of AZ91 composite was explored. The results showed that after 5 vol % Grp was added into the as-cast AZ91 alloy, Mg17Al12 phases were no longer precipitated reticularly along the grain boundary, and Al4C3 phases were formed inside the composite. With the increase in the volume fraction of Grp, the grains of the AZ91 composites were steadily refined. With the increase of forging pass, the grain size of 5% Grp/AZ91 composites decreased first, and then increased. Additionally, the Grp size decreased gradually. There was little change in the yield strength, and the tensile strength and elongation were improved to a certain extent. After forging and extrusion of 5% Grp/AZ91 composites once, the grain size and Grp size were further reduced, and the yield strength, tensile strength, and elongation were increased by 23%, 30%, and 65%, respectively, compared with the composite after forging. With the increase of the number of forging passes before extrusion, the grain size decreased little by little, while the Grp size remained unchanged. The average yield strength, tensile strength, and elongation of the composites after forging and extrusion six times were increased by 3%, 3%, and 23%, respectively, compared with the composite after forging and extrusion once. The wear rate and friction coefficient of the 5% Grp/AZ91 composites decreased after forging once, and the wear mechanism was mainly due to ploughing wear. By comparison, the wear rate and friction coefficient of the 5% Grp/AZ91 composites increased in the extrusion state, and the main wear mechanism was from wedge formation and micro-cutting wear.

Highlights

With the development of miniaturization, and high integration of aerospace, automotive, and electronic equipment, higher requirements for lightweight structural materials have been put forward
Grp size were further reduced, and the yield strength, tensile strength, and elongation were increased by 23%, 30%, and 65%, respectively, compared with the composite after forging
The average yield strength, tensile strength, and elongation of the composites after forging and extrusion six times were increased by 3%, 3%, and 23%, respectively, compared with the composite after forging and extrusion once

Summary

Introduction

With the development of miniaturization, and high integration of aerospace, automotive, and electronic equipment, higher requirements for lightweight structural materials have been put forward. The application of Mg alloys in engineering materials is limited, due to their low modulus, low strength, low hardness, poor wear resistance, high thermal expansion coefficient, and poor high-temperature resistance. Mg matrix composites that are reinforced by adding particles and whiskers feature a good specific modulus, specific strength, wear resistance, adjustable linear expansion coefficient, and so on. They have great potential applications in aerospace, military electronics, automotive, orbital, and other fields [5,6,7,8,9]. It was proven that hot extrusion could improve the distribution of particles in the matrix and the comprehensive mechanical properties of the material

Methods

Results

Conclusion