The Effect of Specimen Size and Test Procedure on the Creep Behavior of ME21 Magnesium Alloy

Bettina Camin,Maximilian Gille

doi:10.3390/cryst11080918

Abstract

Lightweight constructions and materials offer the opportunity to reduce CO2 emissions in the transport sector. As components in vehicles are often exposed to higher temperatures above 40% of the melting temperature, there is a risk of creep. The creep behavior usually is investigated based on standard procedures. However, lightweight constructions frequently have dimensions not adequately represented by standardized specimen geometries. Therefore, comparative creep experiments on non-standardized miniature and standardized specimens are performed. Due to a modified test procedure specified by a miniature creep device, only the very first primary creep stage shows a minor influence, but subsequently, no effect on the creep process is detected. The creep behavior of hot extruded and heat treated ME21 magnesium alloy is investigated. It is observed that the creep parameters determined by the miniature and standard creep tests are different. As the deviations are systematic, qualitatively, evidence of the creep behavior is achieved. The creep parameters obtained, and particularly the creep strain and the strain rate, show a higher creep resistance of the miniature specimen. An initial higher number of twinned grains and possible multiaxiality in the gauge volume of the miniature specimen can be responsible.

Highlights

Since the signing of the Kyoto Protocol and a steadily increasing understanding of the effects of CO2 emissions on the earth’s climate, industry is interested in optimizing its processes and designs regarding CO2 reduction
In this work, the microstructural creep mechanisms activated in the material are independent of the specimen size
The results of the microstructural investigations indicate that the plastic Comparative uniaxial creep measurements ontominiature and specimens deformation of the coarse-grained

Summary

Introduction

Since the signing of the Kyoto Protocol and a steadily increasing understanding of the effects of CO2 emissions on the earth’s climate, industry is interested in optimizing its processes and designs regarding CO2 reduction. In particular, the goal is to lower the overall weight of vehicles, aircraft, and rail vehicles to decrease fuel consumption and environmental pollution. In this context, the terms green technology and life cycle costs focus on product development. Connecting factors are lightweight constructions and materials as well as energy-saving manufacturing processes. In the latter, characterizing the mechanical and thermo-mechanical properties of alloys is critical in developing novel non- or low-contaminant construction and production technologies as well as during operation. The mechanical loads investigated in this work are relatively moderate small dimensions exposed to high temperature can already be rated as highly loaded during service

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