Crystallographic peculiarities of the eutectoid and martensite structures in the U–1.5 % Mo alloy

Using electron microscopy, samples of U–1.5 wt % Mo alloy with a partial structure of eutectoid, which consists of alternating plates of α phase depleted of molybdenum (α-U) and ordered γ’ phase (U2Mo), have been studied. The structures of a eutectoid and martensite have been obtained by the quenching of samples characterized by delayed cooling from 1000°C. It has been shown that, in the eutectoid, the constant orientation relationships (ORs) are observed between the α-U and U2Mo phases, namely, \({\left[ {100} \right]_\alpha }{\left\| {\left[ {331} \right]} \right._{\gamma '}},\;{\left( {010} \right)_\alpha }{\left\| {\left( {11\bar 6} \right)} \right._{\gamma '}},\;{\left( {010} \right)_\alpha }{\left\| {\left( {\bar 110} \right)} \right._{\gamma '}}\) These relationships are similar to the ORs observed in the martensite between an orthorhombic α’ martensite and initial bcc γ phase that have been found in low alloys of U–Nb, U–Zr, U–Mo and experimentally confirmed in this work. It has been established that, in the γ’ phase, principal axes a, b, c remain parallel to the principal axes of the matrix γ phase. However, its axis of tetragonality c has the only nonequivalent crystallographic direction at which the plates in the eutectoid colonies that are parallel to the planes of atomic ordering of the γ’ phase have interphase boundaries of \((001)_{\gamma '} ||(130)_\alpha \).