THE EFFECT OF CARBON ON THE STRUCTURE AND STRENGTH CHARACTERISTICS OF NIOBIUM AND ITS ALLOYS,
Abstract
The microstructure and mechanical properties of niobium alloys containing 0.1, 0.15, or 0.20% carbon, or 16.5% tungsten and 0.1 or 0.15% carbon, or 16.5% tungsten, 0.5% zirconium and 0.1% carbon have been investigated. Alloys were electron-beam melted from sodium-reduced niobium and 99.98%-pure tungsten and zirconium and tested in the as-cast or heat-treated condition. The structure of Nb-C alloy consisted of a homogeneous solid solution containing particles of carbide phase which was identified as Nb2C carbide with a hexagonal structure. No complex carbides were found in ternary Nb-W-C system. The strength of as-cast Nb-C alloys increased with increasing carbon content and reached a maximum of about 23 kg/sq mm at 0.10% C, but the ductility dropped. With further increases in carbon content, both the strength and ductility decreased. Alloy with 0.10-0.15% C was forged with 80% reduction at 1000C without cracks; alloy with 0.20% C, at the same or higher temperature, was unworkable. In Nb-W-C alloys a maximum strength of 50 kg/sq mm was reached at 0.10% C, at which the elongation dropped to 2-5%. The addition of 0.5% zirconium increased the elongation to 10%. 1250C was the minimum temperature required for deformation of Nb-W-C alloy, Nb-C and Nb-W-C alloys with 0.10% C, vacuum-annealed at 1150 and 1400C, respectively, for 2 hr, had a tensile strength of 30.0 and 58.0 kg/sq mm an elongation of 27.0 and 18.7%. Nb-W-Zr-C alloy with 0.10% C had a tensile strength of 70.0 kg/sq mm and an elongation of 27.8%. The effect of alloying becomes especially pronounced at high temperatures. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Mar 28, 1968
- Accession Number
- AD0681593
Entities
People
- I. S. Malashenko
Organizations
- National Air and Space Intelligence Center