Structure and Matrix Microhardness of the 319 Aluminum Alloy After Isothermal Holding During the Solidification Process

摘要

The 319 aluminum alloy is used in a variety of automotive applications. This alloy is typically solution treated in order to improve its metallurgical and mechanical properties. "Traditional" solution treatment involves cooling the castings to an ambient temperature before heating them to the solution temperature; however, some foundries have attempted to institute a more efficient procedure by shortening or eliminating the cooling step. The purpose of this paper is to investigate the effect of isothermal holding during the solidification process on the structure and matrix microhardness of 319 aluminum alloy test samples. The investigation reveals that isothermal holding at approximately 520 deg C minimizes the volume fraction of Cu enriched phases while maximizing the Vickers microhardness of the aluminum matrix. This suggests that 520 deg C is the ideal temperature for solutionizing Cu enriched phases in this alloy. Thermal analysis data from selected experiments are presented for illustrative purposes. This paper represents the first in a series of investigations comparing the properties of castings solution treated using "traditional" methods and those subjected to isothermal holding during the solidification process.