Comprehensive Analysis of Microstructure and Hot Deformation Behavior of Al-Cu-Y-Mg-Cr-Zr-Ti-Fe-Si Alloy

Abstract

Low sensitivity to hot cracking is very important not only for casting but also for ingots of wrought alloys. Doping of Al-Cu-(Mg) alloys by eutectic forming elements provides an increasing resistance to hot cracking susceptibility, but it also leads to a decrease in plasticity. The quasi-binary alloys based on an Al-Cu-REM system with an atomic ratio of Cu/REM = 4 have a high solidus temperature, narrow solidification range and fine microstructure. The detailed investigation of microstructure, precipitation and hot deformation behavior, and mechanical properties of novel Al-Cu-Y-Mg-Cr-Zr-Ti-Fe-Si alloy was performed in this study. The fine Al8Cu4Y, needle-shaped Al11Cu2Y2Si2, compact primary (Al,Ti)84Cu6.4Y4.3Cr5.3 and Q (Al8Cu2Mg8Si6) phases were identified in the as-cast microstructure. Near-spherical coarse Al3(Zr,Y) and fine Al45Cr7 precipitates with a size of 60 nm and 10 nm were formed after 3 h of solution treatment at 580 °C. S′(Al2CuMg) precipitates with an average diameter of 140 nm, thickness of 6 nm and calculated volume fraction of 0.033 strengthened 36 HV during aging at 210 °C for 3 h. Three-dimensional hot processing maps demonstrated an excellent and stable deformation behavior at 440–540 °C and strain rates of 0.01–10 s−1. The rolled sheets had a good combination of yield strength (313 MPa) and plasticity (10.8%) in the recrystallized at 580 °C, with water quenched and aged at 210 °C for a 3 h state. The main calculated effect in the yield strength was contributed by Al45Cr7 precipitates.