An Overview of Dry Sliding Wear of Two-Phase FeNiMnAl Alloys
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An Overview of Dry Sliding Wear of Two-Phase FeNiMnAl Alloys Xiaolan Wu1, Fanling Meng1, Ian Baker1, Hong Wu2 and Paul R. Munroe3 1 Thayer School of Engineering, Dartmouth College, Hanover NH 03755, U.S.A 2 State Key Laboratory of Powder Metallurgy, Central South University, Changsha 410083, P.R.C. 3 Electron Microscope Unit, University of New South Wales, Sydney NSW 2052, Australia ABSTRACT The pin-on-disc wear behavior of nanostructured two-phase Fe30Ni20Mn20Al30 and eutectic lamellar-structured Fe30Ni20Mn35Al15 is compared emphasizing the influence of the microstructure and mechanical properties of alloys as well as the effect of test environment. Although the wear of both alloys was greater in oxygen-containing environments, eutectic Fe30Ni20Mn35Al15 is less sensitive to oxygen than nanostructured Fe30Ni20Mn20Al30. Abrasive wear dominated during the wear in all cases, while plastic deformation also occurred during the wear of eutectic Fe30Ni20Mn35Al15. A tribolayer of zirconia, which was embedded in the surface of the wear pin, was characterized using a scanning transmission electron microscope equipped with an energy dispersive spectrometer. INTRODUCTION Recently, a range of two-phase FeNiMnAl alloys with elemental compositions ranging from 1535 at. % has been investigated for their assorted possible phase transformations and the potential complexity of microstructures and mechanical properties [1]. Detailed microstructural characterization and mechanical properties studies have been performed on two of these alloys, Fe30Ni20Mn20Al30 [2] and Fe30Ni20Mn35Al15 [3]. The former alloy, Fe30Ni20Mn20Al30 [2], consists of (Fe, Mn)-enriched B2 (ordered b.c.c.) and (Ni, Al)-enriched L21 (further ordered B2) phases, which exist in a cube-on-cube relationship. The phase width was ~5 nm for the as-cast alloy (Figure 1(a)), and ~25 nm for the alloy given a 72 h anneal at 823 K (Figure 1(b)) with corresponding Vickers hardness values of 514 Hv and 547 Hv. Both the as-cast and annealed alloy fractured before yield under compression with a fracture strength of ~ 1350 MPa at room temperature. However, the annealed alloy showed a yield strength of ~1450 MPa at 573 K, while at the same temperature, the as-cast alloy still showed a brittle fracture before yielding with a similar fracture strength to that found at room temperature. In contrast, the microstructure of Fe30Ni20Mn35Al15 [3] consists of (Fe, Mn)-enriched f.c.c lamellae with a width of ~500 nm and (Ni, Al)-enriched B2 lamellae with a width of ~200 nm (Figure 1(c)). This novel eutectic alloy showed a yield strength of ~ 600 MPa, a fracture strength of ~ 840 MPa, and an elongation of ~ 8% at room temperature. The hardness of the as-cast alloy is 303 ± 6 HV. In two previous papers the dry sliding wear of Fe30Ni20Al20Al30 [4] and Fe30Ni20Mn35Al15 [5] was studied in different environments using pin-on-disk wear tests with an yttria stabilized zirconia disk. Unfortunately, in those papers pins of different geometry were used and so it was impossible to compare their wear rates.
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