X Ma, R.C. Pond Materials Science and Engineering A 481-482(2008)404-408 twinning plane with the habit plane as depicted in Fig. 1. An [2] J.S. Bowles, J.K. Mac Kenzie, Acta Metall. 2(1954)129, 138, important feature of ferrous alloys is that 1/21 1 l]a disloca- tions are glissile in the terrace plane and hence may be able to [31Jw Christian. The Theory of Transformations in Metals and Alloys, Perg- adjust their line directions after reaching the interface. Moritani [4] C M. Wayman, Introduction to the Crystallography of Martensite Trans- in an Fe-Ni-Mn alloy, the spacing of these dislocations was [5 K. Bains, Macmillan, New York, NY,1964 et al.[21]also observed an array of 1/2[11 1]a LId dislocations d=4.8 nm with 5 close to pure-screw orientation in a habit Inc, New York, NY. 2003. plane with y=1947 and o=1.56. This observation reser [6] P.G. McDougall, C M. Wayman, in: G.B. Olson, w.s. Owen (Eds ) bles the array of bland b=2/-2 defects predicted in Table 3 for The Crystallography and Morphology of Ferrous Martensites, Martensite, American Society for Metals Intemational, USA, 1992 a=1.5, namely: dl=3.76 nm and y=19.80, 5L inclined at [7]RC Pond, S. Celotto, J.P. Hirth, Acta Mater. 51(2003)5385 25.39 to screw. In addition, they were able to image the discon- [8]RC Pond, x. Ma, Y.w. Chai, J.P. Hirth, in: F.R. N. Nabarro, J.P. Hirth nection array using high-resolution TEM. Images obtained with Eds ), Dislocations in Solids, vol. 13, North-Holland, Amsterdam, 2007. the beam direction parallel [1 0 1ly closely resemble the defects [91 j.P. Hirth, J. Phys. Chem. Solids 55(1994)985 in Fig. 4, bearing in mind the screw component of their Burgers [10)R C Pond, S. Celotto, Int. Mater. Rev. 48(2003)225 vectors are not evident in such images. Moreover, the average [11] R.C. Pond, X Ma, J.P. Hirth, Mater. Sci. Eng. A438-440(2006)109 spacing d observed experimentally is in good agreement with [12] J.P. Hirth, J.N. Mitchell, D.S. Schwartz, T.E. Mitchell, Acta Mater. 54 the calculated value of 1.11 nm for b,a defects, Mahon et 20061917 al. [22] and Ogawa and Kajiwara[23] also published images of 3] R.C. Pond, in: ER N Nabarro (Ed ), Dislocations in Solids, vol8, North. disconnection arrays in ferrous alloys; these too are consistent [14)RC Pond, X Ma, Z. Metallkd 96(2005)1124 with the defects illustrated in Fig 4. [15] R.C. Pond, A Serra, D.J. Bacon, Acta Mater. 47(1999)1441 Finally, we note that the LID/disconnection networks pre- [16] B.A. Bilby, R. Bullough, E. Smith, Proc. R. Soc. A 231A(1955) dicted in the present work accommodate misfit on the habit plane of martensite in a manner reminiscent of screw dislocation (18)TNagano, M Enomoto, Metall. Mater. Trans. A 37(2006 networks in grain boundaries between orthorhombic crystals as [191 J.P. Hirth, J Lothe, Theory of Dislocations, second ed,McGraw-Hill,New discussed by Matthews [24]. The present result can be contrasted York. 1982 with misfit-relieving configurations involving edge disconnec- [20] B PJ Sandvik, C M. Wayman, Metall. Trans. A 14(1983)835 tions, as discussed for example by rigsbee and Aaronson[25] 21T. Moritani, N. Miyajima, T. Furuhara, T Maki, Scripta Mater. 47(2002) and Moritani et al. [21]. [22] G.. Mahon, J.M. Howe, S. Mahajan, Philos. Mag. Lett. 59(1989) References [23] K. Ogawa, S Kajiwara, Philos Mag. 84(2004)2919 124 J.w. Matthews, Philos Mag. 29(1974)797. [1] M.S. Wechsler, D.S. Lieberman, T.A. Read, Trans. AIME 197(1953) [25] J.M. Rigsbee. H.L. Aaronson, Acta Metall. 27(1979)36408 X. Ma, R.C. Pond / Materials Science and Engineering A 481–482 (2008) 404–408 twinning plane with the habit plane as depicted in Fig. 1. An important feature of ferrous alloys is that 1/2[1 1 1] ¯ disloca￾tions are glissile in the terrace plane and hence may be able to adjust their line directions after reaching the interface. Moritani et al. [21] also observed an array of 1/2[1 1 1] ¯ LID dislocations in an Fe–Ni–Mn alloy; the spacing of these dislocations was dL = 4.8 nm with L close to pure-screw orientation in a habit plane with ψ = 19.47◦ and ω = 1.56◦. This observation resem￾bles the array of bL and bD −2/−2 defects predicted in Table 3 for ω = 1.5◦, namely: dL = 3.76 nm and ψ = 19.80◦, L inclined at 25.39◦ to screw. In addition, they were able to image the discon￾nection array using high-resolution TEM. Images obtained with the beam direction parallel [1 0 1] ¯ closely resemble the defects in Fig. 4, bearing in mind the screw component of their Burgers vectors are not evident in such images. Moreover, the average spacing dD observed experimentally is in good agreement with the calculated value of 1.11 nm for bD −2/−2 defects. Mahon et al. [22] and Ogawa and Kajiwara [23] also published images of disconnection arrays in ferrous alloys; these too are consistent with the defects illustrated in Fig. 4. Finally, we note that the LID/disconnection networks pre￾dicted in the present work accommodate misfit on the habit plane of martensite in a manner reminiscent of screw dislocation networks in grain boundaries between orthorhombic crystals as discussed by Matthews[24]. The present result can be contrasted with misfit-relieving configurations involving edge disconnec￾tions, as discussed for example by Rigsbee and Aaronson [25] and Moritani et al. [21]. References [1] M.S. Wechsler, D.S. Lieberman, T.A. Read, Trans. AIME 197 (1953) 1503. [2] J.S. Bowles, J.K. MacKenzie, Acta Metall. 2 (1954) 129, 138, 224. [3] J.W. Christian, The Theory of Transformations in Metals and Alloys, Perg￾amon Press, Oxford, UK, 2002. [4] C.M. Wayman, Introduction to the Crystallography of Martensite Trans￾formations, Macmillan, New York, NY, 1964. [5] K. Bhattacharya, Microstructure of Martensite, Oxford University Press, Inc., New York, NY, 2003. [6] P.G. McDougall, C.M. Wayman, in: G.B. Olson, W.S. Owen (Eds.), The Crystallography and Morphology of Ferrous Martensites, Martensite, American Society for Metals International, USA, 1992. [7] R.C. Pond, S. Celotto, J.P. Hirth, Acta Mater. 51 (2003) 5385. [8] R.C. Pond, X. Ma, Y.W. Chai, J.P. Hirth, in: F.R.N. Nabarro, J.P. Hirth (Eds.), Dislocations in Solids, vol. 13, North-Holland, Amsterdam, 2007, p. 225. [9] J.P. Hirth, J. Phys. Chem. Solids 55 (1994) 985. [10] R.C. Pond, S. Celotto, Int. Mater. Rev. 48 (2003) 225. [11] R.C. Pond, X. Ma, J.P. Hirth, Mater. Sci. Eng. A 438–440 (2006) 109. [12] J.P. Hirth, J.N. Mitchell, D.S. Schwartz, T.E. Mitchell, Acta Mater. 54 (2006) 1917. [13] R.C. Pond, in: F.R.N. Nabarro (Ed.), Dislocations in Solids, vol. 8, North￾Holland, Amsterdam, 1989, p. 1. [14] R.C. Pond, X. Ma, Z. Metallkd. 96 (2005) 1124. [15] R.C. Pond, A. Serra, D.J. Bacon, Acta Mater. 47 (1999) 1441. [16] B.A. Bilby, R. Bullough, E. Smith, Proc. R. Soc. A 231A (1955) 263. [17] X. Ma, R.C. Pond, J. Nucl. Mater. 361 (2007) 313. [18] T. Nagano, M. Enomoto, Metall. Mater. Trans. A 37 (2006) 929. [19] J.P. Hirth, J. Lothe, Theory of Dislocations, second ed., McGraw-Hill, New York, 1982. [20] B.P.J. Sandvik, C.M. Wayman, Metall. Trans. A 14 (1983) 835. [21] T. Moritani, N. Miyajima, T. Furuhara, T. Maki, Scripta Mater. 47 (2002) 193. [22] G.J. Mahon, J.M. Howe, S. Mahajan, Philos. Mag. Lett. 59 (1989) 273. [23] K. Ogawa, S. Kajiwara, Philos. Mag. 84 (2004) 2919. [24] J.W. Matthews, Philos. Mag. 29 (1974) 797. [25] J.M. Rigsbee, H.I. Aaronson, Acta Metall. 27 (1979) 365.