微細マーカー法によるFe-Ni合金のマルテンサイト変態に伴うひずみ分布解析

<p>Strain distribution due to martensitic transformation in a Fe-Ni alloy has been investigated using high-precision markers drawn by electron beam lithography. Particular attention has been paid on the strain distribution inside lenticular martensite, which develops in the Fe-31mass%Ni alloy below martensite start temperature:223K. Since the width of the developed lenticular martensite was 5-20 μm, the fine grid marker was drawn in the spacing of 0.5μm on the flat surface of specimen before cooling. The strain distribution evaluated by measuring the displacement of each intersection using the grid marker revealed that the amount of strain at the middle area of the lenticular martensite is larger than that near the grain boundary. This result qualitatively corresponds to an estimated strain distribution by phenomenological theory of martensite crystallography based on the observation of microstructures in lenticular martensite, where the accumulation of fine transformation twins(so-called midrib) is observed in the middle area of the lenticular martensite. This suggests that the measured strain distribution is influenced by manner of lattice invariant deformation accompanied by martensitic transformation. In addition, the effects of electrochemical charged hydrogen on the strain distribution inside lenticular martensite in the Fe-31mass%Ni alloy are also examined.</p>