A Study on Hot Workability of Nb-16Si-22Ti-2Cr-2Al-2Hf-xFe Alloys

Abstract:

Through the research of hot deformation behavior of Nb-16Si-22Ti-2Cr-2Al-2Hf-xFe(x=0、1、2、3、5) alloys, this paper made the hot working diagrams of these alloys which would provides a theoretical basis for subsequent Nb-Si alloys′design and hot working study. The maximum dissipative efficiency factor η appears in the region of low strain rate and high temperature; the minimum appears in low temperature and high strain rate region. There are unstable regions in the thermal processing map of the alloys with different Fe content, mainly distributed in the regions with high strain rate and low temperature, coinciding with the low dissipative efficiency factor regions. The grains in the unstable regions are obviously elongated and the grain boundaries are curved. The grain size is uneven and local plastic flow occurs. The dynamic recrystallization structure exists in the stable deformation zone as well as the fine recrystallized grain is distributed along the grain boundary. With the increase of the deformation temperature and the decrease of the strain rate, the size of the dynamic recrystallization grain increases.

Key words:Power dissipation diagram; Deformation instability diagram; Deformation stability zone