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Title: Refinement of Eutectic Silicon Phase of Aluminum A356 Alloy Using High-Intensity Ultrasonic Vibration

Abstract

The eutectic silicon in A356 alloy can be refined and modified using either chemical, quench, or superheating modification. We observed, for the first time, that the eutectic silicon can also be significantly refined using high-intensity ultrasonic vibration. Rosette-like eutectic silicon is formed during solidification of specimen treated with high-intensity ultrasonic vibration.

Authors:
 [1];  [1]
  1. ORNL
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org.:
USDOE Office of Energy Efficiency and Renewable Energy (EERE)
OSTI Identifier:
1041056
DOE Contract Number:
DE-AC05-00OR22725
Resource Type:
Journal Article
Resource Relation:
Journal Name: Scripta Materialia; Journal Volume: 54; Journal Issue: 5
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; ALLOYS; ALUMINIUM; EUTECTICS; MICROSTRUCTURE; REFINING; SILICON; SOLIDIFICATION; SUPERHEATING; ULTRASONIC WAVES

Citation Formats

Jian, Xiaogang, and Han, Qingyou. Refinement of Eutectic Silicon Phase of Aluminum A356 Alloy Using High-Intensity Ultrasonic Vibration. United States: N. p., 2006. Web. doi:10.1016/j.scriptamat.2005.11.004.
Jian, Xiaogang, & Han, Qingyou. Refinement of Eutectic Silicon Phase of Aluminum A356 Alloy Using High-Intensity Ultrasonic Vibration. United States. doi:10.1016/j.scriptamat.2005.11.004.
Jian, Xiaogang, and Han, Qingyou. Sun . "Refinement of Eutectic Silicon Phase of Aluminum A356 Alloy Using High-Intensity Ultrasonic Vibration". United States. doi:10.1016/j.scriptamat.2005.11.004.
@article{osti_1041056,
title = {Refinement of Eutectic Silicon Phase of Aluminum A356 Alloy Using High-Intensity Ultrasonic Vibration},
author = {Jian, Xiaogang and Han, Qingyou},
abstractNote = {The eutectic silicon in A356 alloy can be refined and modified using either chemical, quench, or superheating modification. We observed, for the first time, that the eutectic silicon can also be significantly refined using high-intensity ultrasonic vibration. Rosette-like eutectic silicon is formed during solidification of specimen treated with high-intensity ultrasonic vibration.},
doi = {10.1016/j.scriptamat.2005.11.004},
journal = {Scripta Materialia},
number = 5,
volume = 54,
place = {United States},
year = {Sun Jan 01 00:00:00 EST 2006},
month = {Sun Jan 01 00:00:00 EST 2006}
}
  • During the application of a structural component, failure by resonant vibration may occur under some abnormal situations. The study of this failure is necessary in order to ensure the reliability of the component. In the current investigation, A356 aluminum alloy (Al-7wt% Si-0.3wt% Mg) was chosen to explore the crack propagation behavior under resonant vibration. This alloy, which contains eutectic silicon particles, has been used as many of the structural components in automobiles and aircrafts. Since the shape and distribution of second phase particles can affect the fatigue crack propagation of a two-phase material, they should also affect the crack propagationmore » under resonant vibration. To study the effect of eutectic silicon morphology and distribution, the A356 alloy was tested under the as-cast condition and two solution-treated conditions.« less
  • In order to investigate the effects of ultrasonic vibration on degassing of aluminum alloys, three experimental systems have been designed and built: one for ultrasonic degassing in open air, one for ultrasonic degassing under reduced pressure, and one for ultrasonic degassing with a purging gas. Experiments were first carried out in air to test degassing using ultrasonic vibration alone. The limitations with ultrasonic degassing were outlined. Further experiments were then performed under reduced pressures and in combination with purging argon gas. Experimental results suggest that ultrasonic vibration alone is efficient for degassing a small volume of melt. Ultrasonic vibration canmore » be used for assisting vacuum degassing, making vacuum degassing much faster than that without using ultrasonic vibration. Ultrasonically assisted argon degassing is the fastest method for degassing among the three methods tested in this research. More importantly, dross formation during ultrasonically assisted argon degassing is much less than that during argon degassing. The mechanisms of ultrasonic degassing are discussed.« less
  • The influences of deformation, heat treatment temperature and holding time on morphology and size distribution of Si containing eutectic phases of Thixocast Al-7Si-0.4 Mg alloy were investigated. The novel thermo-mechanical treatment consisted of initial cold working practice followed by a solution heat treatment at 540 deg. C for durations ranging from 2 min to 120 min followed by water quenching. Optical and scanning electron microscopes were used to study the influence of process parameters on microstructure evolution. Also, final mechanical properties were investigated using hardness test. The results indicate that, under appropriate conditions it is possible to achieve an ultrafinemore » grain microstructure with the eutectic Si fibers fragmented and spheroidized in the entire microstructure. It was also found that, an agglomeration of sphrodized particles occurs and is governed by Ostwald ripening mechanism.« less
  • The wear behavior of A356 aluminum alloy (Al-7 pct Si-0.3 pct Mg) matrix composites reinforced with 20 vol pct SiC particles and 3 or 10 vol pct graphite was investigated. These hybrid composites represent the merging of two philosophies in tribological material design: soft-particle lubrication by graphite and hard-particle reinforcement by carbide particles. The wear tests were performed using a block-on-ring (SAE 52100 steel) wear machine under dry sliding conditions within a load range of 1 to 441 N. The microstructural and compositional changes that took place during wear were characterized using scanning electron microscopy (SEM), Auger electron spectroscopy (AES),more » energy-dispersive X-ray spectroscopy (EDXA), and X0ray diffractometry (XRD). The wear resistance of 3 pct graphite-20 pct SiC-A356 hybrid composite was comparable to 20 pct SiC-A356 without graphite at low and medium loads. At loads below 20 N, both hybrid and 20 pct SiC-A356 composites without graphite demonstrated wear rates up to 10 times lower than the unreinforced A356 alloy due to the load-carrying capacity of SiC particles. The wear resistance of 3 pct graphite 20 pct SiC-A356 was 1 to 2 times higher than 10 pct graphite-containing hybrid composites at high loads. However, graphite addition reduced the counterface wear. The unreinforced A356 and 20 pct SiC-A356 showed a transition from mild to severe wear at 95 N and 225 N, respectively. Hybrid composites with 3 pct and 10 pct graphite did not show such a transition over the entire load range, indicating that graphite improved the seizure resistance of the composites.« less
  • The Bauschinger effect is interpreted as anisotropic work hardening that arises upon reverse loading from internal backstresses that are attributed to dislocations accumulating at obstacles. Studies to describe the Bauschinger effect have either focused on continuum mechanics modeling or on analyzing dislocation build-up at a microscopic scale. In continuum mechanics, the focus often is on the relationship of the ratio of kinematic (anisotropic) hardening to isotropic hardening. In materials science, the focus is often on determining mechanisms related to dislocation arrangement. Few have studied both aspects together and fewer yet have considered cast Al-Si-Mg aluminum alloys. To the author`s knowledge,more » no studies have examined the effect of void damage with regard to second phase particles on the Bauschinger effect for a cast A356 aluminum alloy that was mechanically tested in tension-followed-by-compression and compression-followed-by-tension up to different moderate prestrain levels.« less