Effects of microstructure on Zr-alloy ductility and fracture resistance

The influence of matrix recrystallization grades, intermetallic and hydrides particles on the total and local ductility as well as on the fracture mechanisms in Zr-2,5Nb and Zr-1Nb-1.3Sn-0.4Fe alloys was studied by the methods of acoustic emission (AE), electron microscopy and fractography. Two alternative mechanisms were established of loss of flow stability in alloys under tension. With the uniform distribution of fine particles the flow loses stability on tension (necking) only due to geometrical loss of strength. Aggregates coarse particles available in the structure promote the earlier loss of stability by plastic flow due to microcracking at the stage of uniform deformation. Quantitative relationships between fracture toughness and microstructure of alloys are given. (orig.)