Abstract
Borated stainless steel (BSS) specimens have a boron content of 1.86 wt%, and are prepared by hot isostatic pressing (HIP) conducted at different temperatures, ranging from 1000 to 1100 °C and a constant true strain rate (0.01, 0.1, 1 and 10 s−1). These tests, with observations and microstructural analysis, have achieved the hot deformation characteristics and mechanisms of BSS. In this research, the activation energy (Q) and Zener–Hollomon parameter (Z) were contrasted against the flow curves: Q = 442.35 kJ/mol. The critical conditions associated with the initiation of dynamic recrystallization (DRX) for BSS were precisely calculated based on the function between the strain hardening rate with the flow stress: at different temperatures from 1000 to 1100 °C: the critical stresses were 146.69–254.77 MPa and the critical strains were 0.022–0.044. The facts show that the boron-containing phase of BSS prevented the onset of DRX, despite the saturated boron in the austenite initiated DRX. The microstructural analysis showed that hot deformation promoted the generation of borides, which differed from the initial microstructure of HIP. The inhomogeneous distribution of elements in the boron-containing phase was caused by hot compression.
Highlights
Borated stainless steels (BSS) containing more than 0.1 wt% boron, which are capable of absorbing thermal neutrons due to the high neutron cross-section of isotope 10B [1], are widely used within the nuclear fuel cycle field
BSS fabricated by billet casting [3] or powder metallurgy (PM) [4] need to be heat deformed into the above dimensions
The stress–strain curves demonstrate the distinct classification of mechanisms about dynamic recovery (DRV) and DRX
Summary
Borated stainless steels (BSS) containing more than 0.1 wt% boron, which are capable of absorbing thermal neutrons due to the high neutron cross-section of isotope 10B [1], are widely used within the nuclear fuel cycle field. BBS are used, for example, in spent fuel storage racks [2], which need a neutron absorber sheet or a square tube. BSS fabricated by billet casting [3] or powder metallurgy (PM) [4] need to be heat deformed into the above dimensions. PM is the best choice for those wishing to prepare a homogenous microstructure, and high-performance high-boron stainless steels. The process of hot isostatic pressing (HIP) of metal powders plays an important role in powder metallurgy [5–7]. HIP is a process used to increase the density of powders in a furnace at high pressure (100–200 MPa) and at high temperatures for BSS [4]
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