Application of Rapid Solidification Techniques to Aluminum Alloys
Abstract
This portion of the program was conducted for the purpose of developing a predictive model of heat flow and solidification for aluminum alloys produced under the high cooling rate conditions achievable in atomization processes. It is a combined experimental and theoretical study of the relationship between the important solidification variables (e.g. cooling rate, temperature gradients, interface shape and velocity, supercooling and transformation kinetics) and the structure of rapidly solidified aluminum alloy powders. This report covers that portion of the investigations which addressed the characterization of the thermal history of rapid solidification in metal droplets, and its effects on powder microstructure. The main effort was focused on modelling the heat flow during solidification, and relationships were established between the atomization parameters, the growth kinetics, the interface velocity and undercooling, and other important variables. Numerical solutions based on the enthalpy model were developed, and their results compared to the trends predicted from the Newtonian model. The analysis covered situations of isothermal solidification at the melting temperature, as well as those where significant undercoolings are necessary for nucleation and growth. The implications of single vs. multiple nucleation were also discussed. The concepts developed from the heat flow analysis were coupled to microstructural observations in Aluminum alloy powders, mostly in the submicron size range. It was shown that reducing the particle size decreases the extent of segregation, promotes multiple nucleation and the formation of twins during solidification.
Document Details
- Document Type
- Technical Report
- Publication Date
- Oct 01, 1980
- Accession Number
- ADA096492
Entities
People
- C. G. Lebi
- R. Mehrabian
Organizations
- University of Illinois Urbana–Champaign