Study of creep crack growth in 2618 and 8009 aluminum alloys

Journal Article · Wed Feb 01 04:00:00 EST 1995 · Metallurgical Transactions, A (Physical Metallurgy and Materials Science); (United States)

DOI:https://doi.org/10.1007/BF02664669· OSTI ID:6874607

Leng, Y ^[1]

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1. Hong Kong Univ. of Science and Technology, Sai Kung (Hong Kong). Dept. of Mechanical Engineering

Creep crack growth (CCG) has been investigated in an 8009 (Al-Fe-V-S) P/M alloy at 175 C, 250 C, and 316 C and in a 2618 ingot alloy at 150 C, 175 C, and 200 C. Under sustained load, subcritical crack growth is observed at stress intensity levels lower than K[sub IC]; for 2618, at 200 C, crack growth is observed at stress intensities more than 40 pct lower than K[sub IC]. Alloys 8009 and 2618 exhibit creep brittle behavior, i.e., very limited creep deformation, during CCG. The CCG rates do not correlate with CCG parameters C* and C but correlate with the stress intensity factor, K, and the J integral. Generally, crack growth rates increase with increasing temperature. Micromechanisms of CCG have been studied with regard to microstructural degradation, environmental attack, and creep damage. Although theoretical estimation indicates that CCG resistance decreases with second-phase coarsening, such coarsening has not been observed at the crack tip. Also, no evidence is found for hydrogen- or oxygen-induced crack growth in comparing test results in moist air and in vacuum. Creep deformation and cavitation ahead of crack tip are responsible for observed time-dependent crack growth. Based on the cavitation damage in the elastic field, a micromechanical model is proposed which semiquantitatively explains the correlations between the creep crack growth rate and stress intensity factor K.

• OSTI ID: 6874607
• Journal Information: Metallurgical Transactions, A (Physical Metallurgy and Materials Science); (United States), Journal Name: Metallurgical Transactions, A (Physical Metallurgy and Materials Science); (United States) Vol. 26:2; ISSN 0360-2133; ISSN MTTABN
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360103* -- Metals & Alloys-- Mechanical Properties
ALLOYS
ALUMINIUM ALLOYS
ALUMINIUM BASE ALLOYS
CRACK PROPAGATION
CREEP
IRON ALLOYS
MECHANICAL PROPERTIES
SILICON ALLOYS
TEMPERATURE RANGE
TEMPERATURE RANGE 0400-1000 K
VANADIUM ALLOYS