A study on the effect of $\beta$-heat treatment on the microstructure and mechanical anisotropy in Zircaloy-4 CANDU type fuel cladding was conducted. The heat treatment at 1000, 1050, 1100 and 1200$^\circ$C on Zircaloy tubing was carried out by employing a high frequency vaccum induction heating method. The crystallographic preferred orientation of the cladding was evaluated by the X-ray measurement and was quantitatively analyzed in terms of Kearns texture number, f.
Morphology of second phase particles and $\alpha$-grain of as-received tube were markedly changed by heat treatment. However, they were not much varied by heat treatment temperature conditions. Heat treated Zircaloy tubes exhibited texture changes but the preferred orientation of grains were still remained.
With increasing heat treatment temperatures, the 0.2% yield strength decreased but the hoop strength was not much changed because of changes in preferred orientation as well as $\alpha$-plate width. It was found that the texture parameter, f, values of Zircaloy tubes were influenced by the $\beta$-heat treatment concerning $f_l$, $f_r$ and $f_t$ respectively.
An equation, Y=145$f_l$ + 320, derived in this study to correlate between 0.2% yield strength and $f_l$ values was found to be agreed well with Ballingers' theory. In addition, an experimental work with SEM confirmed the presence of hard and soft grains in the tensile tested matrix of Zircaloy cladding.
A study on the change of mechanical properties and oxidation behavior of Zircaloy-4 fuel cladding after exposing at 900$^\circ$C and 1000$^\circ$C under the steam atomsphere was carried out.
The growth of the $ZrO_2$ layer combined with an oxygen-rich $\alpha$-phase layer into the Zircaloy tube material can be described by an expression, $E = 1.1\sqrt{DT}+2\times10^{-4}$.
The tensile strength of Zircaloy tubes increased for a short period of exposure time and decreased rapidly with further exposure while the hoop strength did not decreased greatly.
In the meantime, the axial and circumferential elongations showed embrittlement phenomena by the drastical decrease with increasing the exposure time.
