Deformation mechanism of reinforcements in Nb4FeSi-containing Nb–Si-based in situ composites: eutectoid transformation and reorientation behavior

Abstract

Nb–Si-based in situ composites are receiving attention as a substitute for Ni-based alloys in aerospace, while poor toughness limits its application. In this work, the toughness of Nb₄FeSi-containing Nb–Si-based alloys was improved by hot deformation. The different deformation behaviors of reinforcements from traditional alloys, including the eutectoid decomposition of β-Nb₅Si₃, and the stacking faults (SFs) and reorientation-induced plasticity (RIP) effect of Nb₄FeSi, are revealed. During hot deformation, the β-Nb₅Si₃ phase undergoes the eutectoid decomposition to obtain the α-Nb₅Si₃ and niobium-based solid solutions (Nbss) phases, which α-Nb₅Si₃ and Nbss satisfy the relationship {110}_α//{110}_Nbss. The [\({1}\overline{1}{\text{0}}\)] SFs and lath-like reoriented variants are formed in the Nb₄FeSi phase, where the matrix and variants follow [001]_m//[111]_v, (\({1}\overline{1}{\text{0}}\) )_m//(\({1}\overline{1}{\text{0}}\) )_v. Furthermore, the interface between matrix and variant is Σ33c symmetrical tilt boundaries, manifested as (\({1}\overline{1}{\text{0}}\))/60°. The fracture toughness of the deformed alloy reaches 18.31 MPa·m^1/2 at 1300 °C/0.005 s⁻¹/0.7, which is 49% higher than the initial alloy.

Graphical abstract