Effects of the quenching temperature on the structures and mechanical properties of Zr-2.5%Nb alloys containing up to 0.3%Ru were studied by opitical and electron microscopy, tensile tests and vickers hardness tests.
In the specimens quenched from the β range or higher temperatures in the α+β range, a martensitic structure was observed. In the twinned martensite plate, (10\bar11) internal-twins were mainly observed with a portion of (10\bar12) internal-twins and dislocations. But in the untwinned martensite plate, internal-twins could not be observed.
In the structure quenched from the temperatures in the α+β range, it was observed that as the quenching temperature decreases, the amount of the α phase increases and the retained β or ω phase occurs at the specified temperatures.
In specimens of furnace-cooled and air-cooled from the β range, parallel plate-like α and basketweave α structures were observed, respectively.
Quenching from the β range or higher temperatures in the α+β range, the tensile strength shows almost a constant value. Further, the decreasing of quenching temperatures shows complicated changes in tensile properties. The minimum and maximum values of tensile strength were observed in relation to the quenched structures of the α with the retained β phase and of the α phase with the quenched ω phase, respectively. In a specimen quenched below 780∼790°C, yield phenomenon was observed in the stress-strain curve.
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