Tensile properties of iron-based P/M steels with ferrite plus martensite microstructure


Gural A. , Tekeli S. , Ando T.

JOURNAL OF MATERIALS SCIENCE, vol.41, no.23, pp.7894-7901, 2006 (Journal Indexed in SCI) identifier

  • Publication Type: Article / Article
  • Volume: 41 Issue: 23
  • Publication Date: 2006
  • Doi Number: 10.1007/s10853-006-0871-4
  • Title of Journal : JOURNAL OF MATERIALS SCIENCE
  • Page Numbers: pp.7894-7901

Abstract

The effect of intercritical heat treatments on the tensile properties of iron-based P/M steels was investigated. For this purpose, atomized iron powder (Ancorsteel 1000) was admixed with 0.3 wt.% graphite powder. Tensile test specimens were cold pressed at 700 MPa and sintered at 1120 degrees C for 30 min under pure argon gas atmosphere. After sintering, similar to 20% pearlite volume fraction in a ferrite matrix was obtained. To produce coarse ferrite + martensite microstructures, the sintered specimens were intercritically annealed at 724 and 760 degrees C and quenched in water. To obtain fine ferrite + martensite microstructures, the sintered specimens were first austenitized at 890 degrees C and water-quenched to produce a fully martensitic structure. These specimens were then intercritically annealed at 724 and 760 degrees C and re-quenched. After the intercritical annealing at 724 and 760 degrees C and quenching, martensite volume fractions were similar to 18% and 43%, respectively, in both the coarse- and fine-grained specimens. Although the intercritically annealed specimens exhibited higher yield and tensile strength than the as-sintered specimens, their elongation values were lower. Specimens with a fine ferrite + martensite microstructure showed high yield and tensile strength and ductility in comparison to specimens with a coarse ferrite + martensite microstructure. The strength values of specimens increased with increasing martensite volume fraction.