Effect of Hot Isostatic Pressing on the Structure and the Mechanical Properties of an Al–7Si–7Cu Composite Alloy

Differential scanning calorimetry and differential barothermal analysis demonstrate that a hydrostatic pressure of 100 MPa leads to a shift in the characteristic temperatures of an aluminum-matrix Al–7 wt % Si–7 wt % Cu composite alloy to higher temperatures at pressure coefficients of 0.04–0.12 K/MPa. An increase in the solidus temperature by 6°C, which is most significant from a practical point of view, is shown to enable one to increase the hot isostatic pressing (HIP) temperature as compared to the homogenizing annealing temperature or the heating temperature for quenching. It is also shown that HIP treatment (the temperature of isothermal holding is 515 ± 5°C, the hydrostatic pressure is 100 MPa, the holding time is 3 h) leads to a more compact morphology of Al₂Cu and Si eutectic particles in the alloy structure. The results of studying the mechanical properties after HIP treatment and hardening heat treatment according to regime T6 (quenching from 505°C for 1 h + aging at 175°C for 6 h) show that the strength of the alloy increases from 335 to 360 MPa, the relative elongation increases by ~35% (from 2.0 to 2.8%) as compared to a usual specimen, and the reproducibility of the mechanical properties is noticeably improved.