The influence of reinforcement particle size distribution on the mechanical behavior of a stainless steel/tin composite
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I. INTRODUCTION
IT has been found that the mechanical behavior of ironbased composites differs from that of the aluminum-based ones. For example, the Al/SiC-composite systems show systematic trends of improved yield strength (0.2. pct proof stress) and ultimate tensile strength (UTS) compared with the relevant matrices.[1] On the other hand, the mechanicaltest data on high-strength steel-based composites, although relatively rare, show that the yield-stress values might be decreased after incorporating the hard reinforcements. In addition, the UTS values are reduced in most cases compared with those of the relevant matrices.[2,3,4] In recent years, the industrial interest in iron-based composites has been growing due to the need for materials with combined properties.[5–9] The aim, of the present study is to develop a stainless steelbased composite for potential applications in petrochemical, chemical, energy, and manufacturing industries. Good wear, high mechanical strength, and sufficient corrosion resistance are required for these applications. In this article, the results of selected tests that reveal the mechanical behavior of the composites are presented. In the discussion, attention is given to the influence of the microstructural change of the matrix and the particle-size distribution of the reinforcement on the composite properties. In addition, the nature of the metal/ceramic interface and its influence on the composite properties are also investigated. II. MATERIALS AND EXPERIMENTAL PROCEDURE A. Materials and Composite processing A powder-metallurgical, superaustenitic stainless steel (Avesta Sheffield 654SMO) with a particle size of ,45 mm was chosen as the matrix material. The reinforcement was
X. LIU and J. HELLMAN, Researchers, E. PAGOUNIS, D.Sc., and V.K. LINDROOS, Professor, are with the Laboratory of Physical Metallurgy and Materials Science, Helsinki University of Technology, FIN-02015 HUT, Finland. Manuscript submitted November 13, 1998. METALLURGICAL AND MATERIALS TRANSACTIONS A
particulate TiN with an initial size distribution of 5 to 36 mm. Table I lists the chemical composition of the matrix. Selected properties of the materials involved are given in Table II. The composites were produced through a powder-metallurgical route with hot-isostatic pressing (“hipping”) consolidation. The hipping parameters were determined by referring to the previous experience. Accordingly, the capsules were held at 1180 8C in an argon atmosphere under the pressure of 100 MPa for 3 hours. The capsules were then solution annealed at 1180 8C for 1 hour and quenched by pressed air to ensure that the matrix was free from sigma phase, which might precipitate (in high Cr steels) during the slow cooling step in the Hipping cycle (from 820 8C to room temperature). Two sets of composites reinforced with 10, 20, and 30 vol pct TiN were produced. In set 1, the matrix was reinforced with the TiN particles of a wide size distribution (5 to 36 mm). In set 2, sieved TiN particles with a narrowed size distribution (20 to 36
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