High-Temperature Compressive Creep Properties and Mechanisms of Ti-43Al-6Nb-1Mo-1Cr Alloy Reinforced with B4C

Abstract:

The effect of B₄C addition on the high-temperature compressive creep behavior of a β-solidified γ-TiAl-based alloy under the conditions of 250 MPa/800?850 ℃ and 850 ℃/200?250 MPa was investigated. The results show that the reinforcement of the Ti-43Al-6Nb-1Mo-1Cr alloy with B₄C significantly enhances its high-temperature compressive creep property. This improvement is reflected by a reduction in steady-state creep rate of 38.42% and a decrease in creep strain after 50 h of 46.32%. The steady-state creep rate of alloys as a function of stress and temperature follows the Norton-Bailey power-law model. With the addition of B₄C, the stress exponent increases from 1.96 to 4.16, and the creep activation energy rises from 335.02 kJ/mol to 368.52 kJ/mol. This change indicates a transition in dominant deformation mechanism from grain-boundary sliding to dislocation climb. The remarkable enhancement in compressive creep resistance is attributed to multiple strengthening effects. The precipitated rod-like TiB acts as a hard second phase that strengthens the matrix by hindering dislocation motion and pinning grain boundaries. In synergy with C dissolved in the matrix, it also refines the lamellar clusters. The addition of 0.2at% B₄C notably suppresses dynamic recrystallization, thereby delaying degradation of the lamellar structure and mitigating the softening effect induced by recrystallization. Furthermore, Ti₂AlC and Ti₂Al particles precipitate dynamically during high-temperature compressive creep, pinning at the α₂ phase interfaces and within the B2 phase, respectively. These precipitates strengthen the crystal structure and improve the microstructural stability of the alloy.