Microstructural development of rapid solidification in Al-Si powder

Thesis/Dissertation · Tue Sep 26 04:00:00 EDT 1995

DOI:https://doi.org/10.2172/130619· OSTI ID:130619

Jin, Feng ^[1]

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1. Iowa State Univ., Ames, IA (United States)

The microstructure and the gradient of microstructure that forms in rapidly solidificated powder were investigated for different sized particles. High pressure gas atomization solidification process has been used to produce a series of Al-Si alloys powders between 0.2 μm to 150 μm diameter at the eutectic composition (12.6 wt pct Si). This processing technique provides powders of different sizes which solidify under different conditions (i.e. interface velocity and interface undercooling), and thus give different microstructures inside the powders. The large size powder shows dendritic and eutectic microstructures. As the powder size becomes smaller, the predominant morphology changes from eutectic to dendritic to cellular. Microstructures were quantitatively characterized by using optical microscope and SEM techniques. The variation in eutectic spacing within the powders were measured and compared with the theoretical model to obtain interface undercooling, and growth rate during the solidification of a given droplet. Also, nucleation temperature, which controls microstructures in rapidly solidified fine powders, was estimated. A microstructural map which correlates the microstructure with particle size and processing parameters is developed.

• Research Organization: Ames Lab., IA (United States)
• Sponsoring Organization: USDOE
• DOE Contract Number: W-7405-ENG-82
• OSTI ID: 130619
• Report Number(s): IS-T--1755; ON: DE96002244
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ALUMINIUM ALLOYS
ATOMIZATION
DENDRITES
HARDNESS
MICROSTRUCTURE
MORPHOLOGY
PARTICLE SIZE
PHASE DIAGRAMS
POWDERS
SILICON ALLOYS
SOLIDIFICATION