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  1. Improving the Ductility of Fe30Ni20Mn35Al15via Cr Additions Ian Baker, Dartmouth College, DMR 0905229 The effects of different amounts of Cr on the microstructure and tensile properties of as-cast 30Fe-20Ni-35Mn-15Al have been studied. Both scanning electron microscope and transmission electron microscope images showed that the alloys consisted of lamellar B2 (ordered b.c.c.) and f.c.c. phases when the Cr content was ≤ 6 at.% (Figure 1), but that the addition of 8 at. % Cr, led to the appearance of a three-phase, non-lamellar microstructure. Room temperature tensile tests, performed at a strain rate of 5 x 10-4 s-1, showed that the ductility increased sharply with increasing Cr content up to 6 at. % Cr, but decreased dramatically at 8 at. % Cr(Figure 2) corresponding to the change in microstructure. Concurrent with the increase in ductility, the yield stress decreased slightly as the Cr content increased to 6 at. %, but then increased when the Cr addition was 8 at.%(Figure 2). Figure 1: (a) Bright field TEM image of Fe29Ni19Mn34Al14Cr4 showing alternating B2 and f.c.c. phases, and (b, c) X-ray spectra from the two phases showing that the Cr resides mainly in the f.c.c. phase.

  2. Improving the Ductility of Fe30Ni20Mn35Al15via Cr Additions Ian Baker, Dartmouth College, DMR 0905229 The research was performed by the Ph.D.candidate, FanlingMeng, and the P.I., Ian Baker, assisted by Curtis Lim, a Dartmouth undergraduate student. The structural applications of many intermetallic compounds have been limited due to their brittleness at room temperature. While Cr additions improve the ductility of this particular alloy, Fe30Ni20Mn35Al15, the approach used suggests that appropriate alloying may improve the ductility of other alloys with similar microstructures. Figure 2: (a) Strain-stress curves for Fe30Ni20Mn35Al15 containing different amounts of Cr tensile tested at a strain rate of 5×10-4 s-1 at room temperature, and (b) UTS, yield stress and elongation as a function of at. % Cr added to Fe30Ni20Mn35Al15.