Mechanical properties and thermal deformation behavior of low-cost titanium matrix composites prepared by a structure-optimized Y₂O₃ crucible

Abstract

A porous yttrium oxide crucible with both thermal shock resistance and erosion resistance was developed by structural optimization. The structure-optimized yttrium oxide crucible was proved to be suitable for melting highly reactive titanium alloys. Low-cost (TiB + Y₂O₃)-reinforced titanium matrix composites were prepared by vacuum induction melting using the prepared crucible. The thermal deformation behavior and microstructure evolution of (TiB + Y₂O₃)-reinforced titanium matrix composites were investigated at deformation temperatures of 900–1100 °C with strain rates of 0.001–1 s⁻¹. The results showed that the prepared yttrium oxide crucible had both thermal shock and erosion resistance, the low-cost titanium matrix composites could be prepared by the developed yttrium oxide crucibles which were homogeneous in composition and highly sensitive to strain rate and deformation temperature, and the peak and rheological stresses decreased with increasing deformation temperature or decreasing strain rate. In addition, the average thermal deformation activation energy of the composites was calculated to be 574.6 kJ/mol by establishing the Arrhenius constitutive equation in consideration of the strain variables, and the fitting goodness between the predicted stress value and the measured value was 97.624%. The calculated analysis of the hot processing map showed that the best stable thermal deformation zone was located in the deformation temperature range of 1000–1100 °C and strain rate range of 0.001–0.01 s⁻¹, where the peak dissipation coefficient was η = 71%. In this zone, the deformation of the reinforcement and matrix was harmonious, the reinforcement was less likely to fracture, dynamic recrystallization occurred more fully and the alloy exhibited near steady rheological characteristics.