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Title: The debonding and fracture of Si particles during the fatigue of a cast Al-Si alloy

Abstract

Constant-amplitude high-cycle fatigue tests ({sigma}{sub max} = 133 MPa, {sigma}{sub max}/{sigma}{sub y} = 0.55, and R = 0.1) were conducted on a cylindrical samples machined from a cast A356-T6 aluminum plate: The fracture surface of the sample with the smallest fatigue-crack nucleating defect was examined using a scanning electron microscope (SEM). For low crack-tip driving forces (fatigue-crack growth rates of da/dN {lt} 1 x 10{sup {minus}7} m/cycle), the authors discovered that a small semicircular surface fatigue crack propagated primarily through the Al-1% Si dendrite cells. The silicon particles in the eutectic remained intact and served as barriers at low fatigue-crack propagation rates. when the semicircular fatigue crack inevitably crossed the three-dimensional Al-Si eutectic network, it propagated primarily along the interface between the silicon particles and the Al-1% Si matrix. Furthermore, nearly all of the silicon particles were progressively debonded by the fatigue cracks propagating at low rates, with the exception of elongated particles with a major axis perpendicular to the crack plane, which were fractured. As the fatigue cracks grew with a high crack-tip driving force (fatigue-crack growth rates of da/dN {gt} 1 x 10{sup {minus}6} m/cycle), silicon particles ahead of the crack tip were fractured, and the crack subsequentlymore » propagated through the weakest distribution of prefractured particles in the Al-Si eutectic. Only small rounded silicon particles were observed to debond while the fatigue crack grew at high rates. Using fracture-surface markings and fracture mechanics, a macroscopic measure of the maximum critical driving force between particle debonding vs fracture during fatigue-crack growth was calculated to be approximately K{sub max}{sup tr} {approx} 6.0 MPa {radical}m for the present cast A356 alloy.« less

Authors:
; ; ; ;
Publication Date:
Research Org.:
Univ. of Colorado, Boulder, CO (US)
Sponsoring Org.:
USDOE
OSTI Identifier:
20005976
DOE Contract Number:  
AC04-94AL85000
Resource Type:
Journal Article
Journal Name:
Metallurgical and Materials Transactions. A, Physical Metallurgy and Materials Science
Additional Journal Information:
Journal Volume: 30; Journal Issue: 12; Other Information: PBD: Dec 1999; Journal ID: ISSN 1073-5623
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; FATIGUE; FRACTURE PROPERTIES; ALUMINIUM ALLOYS; SILICON ALLOYS; PARTICULATES; CRACKS; CRACK PROPAGATION; INTERFACES; FRACTURE MECHANICS

Citation Formats

Gall, K, Yang, N, Horstemeyer, M, McDowell, D L, and Fan, J. The debonding and fracture of Si particles during the fatigue of a cast Al-Si alloy. United States: N. p., 1999. Web. doi:10.1007/s11661-999-0218-2.
Gall, K, Yang, N, Horstemeyer, M, McDowell, D L, & Fan, J. The debonding and fracture of Si particles during the fatigue of a cast Al-Si alloy. United States. https://doi.org/10.1007/s11661-999-0218-2
Gall, K, Yang, N, Horstemeyer, M, McDowell, D L, and Fan, J. 1999. "The debonding and fracture of Si particles during the fatigue of a cast Al-Si alloy". United States. https://doi.org/10.1007/s11661-999-0218-2.
@article{osti_20005976,
title = {The debonding and fracture of Si particles during the fatigue of a cast Al-Si alloy},
author = {Gall, K and Yang, N and Horstemeyer, M and McDowell, D L and Fan, J},
abstractNote = {Constant-amplitude high-cycle fatigue tests ({sigma}{sub max} = 133 MPa, {sigma}{sub max}/{sigma}{sub y} = 0.55, and R = 0.1) were conducted on a cylindrical samples machined from a cast A356-T6 aluminum plate: The fracture surface of the sample with the smallest fatigue-crack nucleating defect was examined using a scanning electron microscope (SEM). For low crack-tip driving forces (fatigue-crack growth rates of da/dN {lt} 1 x 10{sup {minus}7} m/cycle), the authors discovered that a small semicircular surface fatigue crack propagated primarily through the Al-1% Si dendrite cells. The silicon particles in the eutectic remained intact and served as barriers at low fatigue-crack propagation rates. when the semicircular fatigue crack inevitably crossed the three-dimensional Al-Si eutectic network, it propagated primarily along the interface between the silicon particles and the Al-1% Si matrix. Furthermore, nearly all of the silicon particles were progressively debonded by the fatigue cracks propagating at low rates, with the exception of elongated particles with a major axis perpendicular to the crack plane, which were fractured. As the fatigue cracks grew with a high crack-tip driving force (fatigue-crack growth rates of da/dN {gt} 1 x 10{sup {minus}6} m/cycle), silicon particles ahead of the crack tip were fractured, and the crack subsequently propagated through the weakest distribution of prefractured particles in the Al-Si eutectic. Only small rounded silicon particles were observed to debond while the fatigue crack grew at high rates. Using fracture-surface markings and fracture mechanics, a macroscopic measure of the maximum critical driving force between particle debonding vs fracture during fatigue-crack growth was calculated to be approximately K{sub max}{sup tr} {approx} 6.0 MPa {radical}m for the present cast A356 alloy.},
doi = {10.1007/s11661-999-0218-2},
url = {https://www.osti.gov/biblio/20005976}, journal = {Metallurgical and Materials Transactions. A, Physical Metallurgy and Materials Science},
issn = {1073-5623},
number = 12,
volume = 30,
place = {United States},
year = {Wed Dec 01 00:00:00 EST 1999},
month = {Wed Dec 01 00:00:00 EST 1999}
}