Showing 3 results for Niobium
A. Noorian, Sh. Kheirandish, H. Saghafian,
Volume 7, Issue 2 (6-2010)
Abstract
Abstract:
mechanical properties of AISIH 13 hot-work tool steel have been studied. Cast samples made of the modified new steel were homogenized and austenitized at different conditions, followed by tempering at the specified temperature ranges. Hardness, red hardness, three point bending test and Charpy impact test were carried out to evaluate the mechanical properties together with characterizing the microstructure of the modified steel using scanning electron microscope. The results show that niobium addition modifies the cast structure of Nb–alloyed steel, and increases its maximum hardness. It was found that bending strength bending strain, impact strength, and red hardness of the modified cast steel are also higher than those of the cast H13 steel, and lower than those of the wrought H13 steel.
In this research, the effects of partially replacing of vanadium and molybdenum with niobium on the
Reza Soleimani Gilakjani, Seyed Hossein Razavi, Masoumeh Seifollahi,
Volume 18, Issue 1 (3-2021)
Abstract
Niobium addition is an appropriate approach for improvement of superalloy’s operation. The purpose of this study is twofold: (1) to investigate on the η and γ/ phase precipitations along with (2) to identify the high-temperature tensile properties in A286 and Nb-A286, as a modified type. The heat treatment of both alloys was carried out in a two-stage aging procedure at 760°C for 16 h and 820°C for 2 to 30 hours, following characterized by optical and Scanning electron (SEM-EDS) microscopies, differential thermal analysis (DTA) and high temperature tensile tests. The results showed that niobium addition was increased the volume fraction of γ/ phase, from 10.7% to 12%, decreased its size, from 94 to 71 nm, and rising the γ/-dissolution temperature from 987°C to 1007°C. Moreover, the γ/ to η phase transformation was sluggishly occurred in Nb-A286 due to more stable of γ/ precipitations. Furthermore, the Nb-A286 alloy demonstrates higher mechanical properties than A286 one, approximately 100MPa improvement, which it was contributed to the much large volume fraction and finer size of more stabilized γ/ phase.
Hossein Momeni, Sasan Ranjbar Motlagh,
Volume 21, Issue 3 (9-2024)
Abstract
The present work deals with the hot deformation behavior of commercial Nb alloy C-103 and its microstructure evolution during uniaxial compression tests in the temperature range of 700-1100 °C and the strain rate range of 0.001-0.4 s-1. Strain rate sensitivity, calculated from the compression tests data, was almost constant and showed a negative value in the temperature range of 700-900 °C but increased significantly beyond 900 °C. Dynamic strain aging was found to have a predominant effect up to 900 °C, beyond which dynamic recovery and oxidation influenced the compressive properties. The microstructure of the deformed samples showed indications of dynamic recrystallization within the high strain rate sensitivity domain and features of flow instability in the regime of low strain rate sensitivity. The 950–1000 °C temperature range and strain rate range of 0.001-0.1 s-1 were suggested as suitable hot deformation conditions. The constitutive equation was established to describe the alloy's flow behavior, and the average activation energy for plastic flow was calculated to be 267 kJ/mol.
