Ductile to brittle transition in magnesium alloy with a crack

Toshiyuki Ishina, Shigeru Hamada, Hiroshi Noguchi

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Abstract

We evaluated the strength of a cast non-combustible magnesium alloy that is intended for use in automobile engines. This alloy contains thin sheet-like oxides because of its production process. The size of these thin sheet-like oxides varies, and this means that the temperature dependency of the strength characteristics of the alloy cannot be determined by a tensile test alone. Initially, specimens of the alloy having an artificial pre-crack of 5 [mm] to simulate the sheet-like oxides were subject to tensile testing. The testing was carried out at room temperature (23 [°C]), 150 [°C], 200 [°C] and 250 [°C]. 250 [°C] is the temperature of the environment in which the alloy will be used in automobile engines. All the fractures propagated from the artificial pre-crack and the alloy exhibited its maximum strength at 150 [°C]. To investigate the temperature dependency of the fracture mechanism, a scanning electron microscope (SEM) was used to observe the region near the tip of the pre-crack on the fracture surface of the specimens tested at room temperature and at 250 [°C]. On the fracture surface of the specimen tested at 250 [°C], some dimples were observed over some of the surface near the tip of the artificial pre-crack; however, the fracture surface of the specimen tested at room temperature showed brittle fracture surface morphology over the entire area. For the magnesium alloy, the critical resolved shear stress for non-basal slip, which is a characteristic of a hexagonal close-packed metal, is dependent on temperature. Therefore, ductile to brittle transition was considered to be occurred at a temperature between room temperature and 250 [°C]. Mechanical restraint is also considered to be affected the ductile to brittle transition.

Original languageEnglish
Title of host publication19th European Conference on Fracture
Subtitle of host publicationFracture Mechanics for Durability, Reliability and Safety, ECF 2012
PublisherEuropean Conference on Fracture, ECF
ISBN (Print)978-5-905576-18-8
Publication statusPublished - Jan 1 2012
Event19th European Conference on Fracture: Fracture Mechanics for Durability, Reliability and Safety, ECF 2012 - Kazan, Russian Federation
Duration: Aug 26 2012Aug 31 2012

Publication series

Name19th European Conference on Fracture: Fracture Mechanics for Durability, Reliability and Safety, ECF 2012

Other

Other19th European Conference on Fracture: Fracture Mechanics for Durability, Reliability and Safety, ECF 2012
CountryRussian Federation
CityKazan
Period8/26/128/31/12

All Science Journal Classification (ASJC) codes

  • Safety, Risk, Reliability and Quality

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