Statistical approach to experimental design to determine the effect of extrusion variables on the mechanical properties of an Al-Li alloy

The objective of this research study was to utilize the statistical design of experiments method to analyze and evaluate the influence of the extrusion process manufacturing parameters on some given mechanical properties for an aluminum-lithium alloy with a given composition and post-extrusion thermal processing. The goal was to analyze and determine if variations in specific extrusion processing variables or parameters had a statistically significant effect on some given mechanical properties such as yield strength, ultimate tensile strength, and ductility. The layout for the design experiment consisted of two extrusion temperatures and two extrusion geometries. The layout also included six cross section areas nested in two extrusion geometries. Thus, the design of the experiment was a mixture of a nested structure and a factorial structure, i.e. a nested factorial design. This design included interactions crossed between the extrusion temperature and the extrusion geometry, and the extrusion temperature with the cross sectional area. Thus, there was a possibility of twelve different treatment combinations that made up the design of experiments method. It was found that the extrusion geometry was at least 95% statistically significant with respect to the mechanical properties of interest and that the extrusion temperature was not significant at this level