Crystallographic orientation relationships between intragranular ferrites, the MnSϩV(C, N) complex precipitates acting as ferrite nucleation sites, and austenite matrix were studied in Fe-Mn-C alloys by scanning electron and transmission electron microscopy. VC holds a cube-cube orientation relationship (͗001͘ g // ͗001͘ VC ) when it is formed directly within austenite grains in an Fe-12Mn-0.8C-0.3V alloy. When VC precipitates nucleate on incoherent MnS particles dispersed in austenite, there is no specific orientation relationship between the three phases. Intragranular ferrite idiomorphs nucleating on the MnSϩV(C, N) complex precipitate in austenite in Fe-1.5Mn-0.2C and Fe-2Mn-0.2C alloys often hold the Baker-Nutting orientation relationship ((001) a //(001) V(C, N) , [110] a //[100] V(C, N) ). Although several irrational ferrite/ V(C, N) orientation relationships were observed, misorientation for either low-index planes or directions are relatively small between ferrite and V(C, N) for those relationships. The orientation relationships between intragranular ferrite and austenite were estimated by examining the misorientations between the ferrite and the neighboring martensite lathes from the Kurdjumov-Sachs inter-variant relationships. There is no specific orientation relationship between the intragranular ferrite idiomorph and the austenite matrix because of the low-energy orientation relationships between ferrite and V(C, N).KEY WORDS: phase transformation; precipitation; steel; austenite; ferrite; carbide; nitride; sulfide; inclusion; crystallography; interface.involved for intragranular ferrite transformation.In the present study, the detail of multiphase relationship between ferrite, MnSϩV(C, N) complex precipitate and austenite is discussed based on the observation using scanning and transmission electron microcopy. Table 1 shows the chemical composition of the alloys used in the present study. In an Fe-20Cr-10Ni austenitic alloy which contains a small amount of Mn and S, MnS is fully dissolved in austenite by the solutionizing at 1 473 K and precipitate during aging at 1 273 K based on the calculation with the equation proposed by Turkdogan. Experimental Procedure10) The solution temperatures of MnS in austenite for the other three alloys are well above the melting temperature of austenite, and thus, MnS cannot be dissolved in austenite after solidification. In an Fe-12Mn-0.8C-0.3V austenitic alloy which was used in the study on intragranular pearlite transformation, 7) V(C, N) can be dissolved into austenite by solutionizing treatments at high temperatures and precipitate during aging at lower temperatures. Thus, in this alloy, the measurement of precipitate/austenite orientation relationship was made both for coherent VC which precipitate directly in austenite as well as incoherent MnSϩVC complex precipitate. The solution temperatures of V(C, N) were estimated from the Thermo-Calc calculation. The specimens were homogenized at 1 473 K for 86.4 ks, cold rolled by 70 % and solution treated at 1 473 K...

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We investigated the decomposition reaction mechanism of a molybdenum dithiocarbamate (MoDTC) molecule using computational chemistry methods: density functional theory and hybrid quantum chemical/classical molecular dynamics methods. The density functional theory results showed that the linkage isomerization reaction of the MoDTC preferentially takes place than its direct decomposition reaction. During a hybrid quantum chemical/classical molecular dynamics simulation, the linkage isomer of MoDTC was observed and subsequently bond weakening of its MoO was also observed in the polyalphaolefine phase. From these results, we proposed a new decomposition reaction pathway of the MoDTC molecule: it first forms its linkage isomer as the intermediate in the engine oil phase then decomposes into molybdenum disulfide and monothiocarbamic acid molecules on the rubbing nascent surfaces.