Formation mechanism of weak ferrite areas in Ni-containing powder metal steels and methods of strengthening them

MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING

卷:527

Article

Wu, M. W.²  Hwang, K. S.¹ 

[1] Natl Taiwan Univ, Dept Mat Sci & Engn, Taipei 106, Taiwan

[2] Natl Formosa Univ, Dept Mat Sci & Engn, Huwei Township 632, Yunlin County, Taiwan

关键词: Sintering;    Powder metallurgy;    Homogenization;    Diffusion couple;    Fracture;    Alloy design;   

DOI  :  10.1016/j.msea.2010.05.089

来源: Elsevier

【 摘 要 】

The mechanical properties of Ni-containing powder metal steels are typically inferior to those of their wrought counterparts due to the presence of pores and soft Ni-rich/C-lean ferrite. To improve the mechanical properties, the distribution of alloying elements and the formation mechanism of the soft Ni-rich/C-lean areas were investigated. The results of diffusion couple experiments showed that a soft ferrite layer formed between martensite and pearlite phases. When Cr and Mo were added, the distribution of Ni and C improved and the ferrite disappeared. As a result, the tensile strength increased because the fracture path changed by passing through pearlite or along pearlite/martensite boundaries, instead of passing through ferrite. Based on the microstructure and diffusion couple results, schematics were presented to explain the formation mechanism of the weak Ni-rich/C-lean ferrite and its elimination by adding Cr and Mo. (C) 2010 Elsevier B.V. All rights reserved.

【 授权许可】

Free