Indirect squeeze casting of ZM5 baffle with linear segregation and its formation mechanism

Abstract

Macro-segregation in squeeze casting leads to inhomogeneous compositional distribution and degradation of mechanical properties. The distribution and formation mechanism of segregation in squeeze casting baffle were investigated by combining simulation software and experiments. The results showed that the segregation in the baffle was mainly distributed in the abrupt transition region of wall thickness. The evolution of segregation was simulated by the phase-field method to study the formation mechanism of segregation. During the solidification of the casting, pressure is applied to force the metal fluid to convect and complement the shrinkage, and the high solute content metal fluid meets in the wall thickness transition region. Highly brittle precipitated phases with overly dense distribution of segregation areas are easy to cracking during the load loading process, which leads to simultaneous cracking of the matrix through the extension of cracks into the matrix by means of load transfer. The T6 (410 °C × 20h + 200 °C × 8h) heat treatment process can reduce the segregation by dissolving the agglomerated island eutectic tissues into the matrix and then aging them uniformly with granular precipitation. The tensile strength of the castings after T6 treatment increased from 172 MPa (141 MPa at the segregation position) to 245 MPa, and the elongation was 3.3 %.