Mechanical and microstructural behaviour of a particulate reinforced steel for structural applications

Abstract

Low density, high modulus, and potentially improved wear resistance are the major bene®ts of a ferrous composite material. A BS S.156 (4%NiCrMo) gear steel reinforced with 15 vol.-% titanium diboride particles has been demonstrated for possible high performance structural applications. This composite has been produced by a powder metallurgy/mechanical milling processing route, to give a homogeneous distribution of ®ne reinforcement particles. The composite tensile strength was 90% of the matrix in the fully heat treated condition, with ductility of up to 6%. However, martensite formation and hence the hardenability was found to be suppressed in the composite. A fatigue study indicated that the titanium diboride particles did not appear to contribute to crack initiation in the composite. MST/4531At the time of writing Miss Kukilowski, Mrs Godfrey, Dr Wisbey, and Dr Goodwin were in the Mechanical Sciences Sector,

Microstructure refinement for high modulus in-situ metal matrix composite steels via controlled solidification of the system Fe–TiB2

“…The tensile elongation was for instance found to be almost halved by the incorporation of just 10 vol.% TiB 2 with a morphology and dispersion comparable to our VIM and ARC experiments [25]. While the exact interaction between soft and ductile metallic matrix and the hard and stiff ceramic particles during co-deformation is complex and still not fully understood [31,32,42,43], the unfavourable ductility can be assumed to be mainly caused by the irregular dispersion of comparatively large and sharp-edged particles acting as stress concentrators. This is corroborated by results from powder metallurgy experiments, where the dispersion of particles is easily controlled, but their morphology and size and thus the bulk materialś ductility are nevertheless not satisfactory [44].…”

“…However, the addition of such inherently brittle ceramic particles (K IC of TiB 2 $ 4 -7 MPa m 1/2 [27]) significantly deteriorates the materials' toughness and ductility [25,[31][32][33][34]. This becomes especially relevant for the pseudo-binary system Fe-TiB 2 , where the large TiB 2 fractions (above $15 vol.%) required for significant effects on E and q result in the formation of sharp-edged eutectic lamellae and coarse hyper-eutectic particles from the melt (eutectic concentration about 6.3 mol.% TiB 2 , [28,30]).…”

Anisotropic elastic constants and thermal expansivities in monocrystal CrB2, TiB2, and ZrB2

“…For example, TiB 2 has often been used as reinforcements in various composite materials such as steel [4]. TiB 2 has also been considered in applications in diffusion barriers for preventing electromigration in very large-scale integrated (LSI) circuits because of the very low diffusion coefficient [5].…”

Interfaces and defects in a successfully hot-rolled steel-based composite Fe–TiB 2

“…Powder metallurgy processes allow adjustment of the composition, fraction and distribution of the reinforcements (Fe-TiC [9]), (Fe-TiB 2 [10][11][12][13][14]). However, they require a good control of the reactivity between phases so as to avoid the formation of a brittle interfacial layer.…”