| In order to investigate the characteristics of mechanical properties, the strengthening effects and strengthening mechanisms of ausformed martensite prepared by ausforming treatment in Fe-30% Ni alloy and Fe-30% Ni-0.1% C alloy, optical and electron microstructures, amounts of retained austenite and mechanical properties such as hardness, yield strength, ultimate tensile strength and elongation were examined. The results obtained in this study are as follows: 1. Ausformed martensite is plate type martensite coexisted with midrib twin and partly tangled dislocation, and has a dislocation cell structure formed from the tangled dislocation in high deformation degrees. 2. Although the increment of strength induced by deforming austenite is not entirely inherited by ausformed martensite, the strength of ausformed martensite in two alloys shows a remarkable increment with increasing deformation degrees. 3. Ausformed martensite of Fe-30% Ni-0.1% C alloy shows more increasing rate of strength thant that of Fe-30% Ni alloy. 4. Elongation of austenite is rapidly decreased with increasing deformation degrees. However elongation of ausformed martensite shows a nearly constant value independent of deformation degree because of the formation of ductile matrix. 5. The strengthening mechanisms of ausformed martensite in two alloys are considered to be the multiple strengthening effects caused by the inheritance of lattice defects from deformed austenite, the refinement of martensite plate and substructure induced from martensite transformation. |
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