变形及热处理对Zr-Sn-Nb合金中β-Zr分解的影响

Effect of the Deformation and Heat Treatment on the Decomposition of a Zr in Zr-Sn-Nb Alloys

用透射电子显微镜研究了变形及热处理对Zr-Sn-Nb合金中β-Zr分解的影响。试样经750℃,0.5h处理快冷后,在晶界上形成块状的β-Zr,在晶粒内形成棒状的β-Zr;经1000℃,0.5h处理快冷后,在板条晶粒的晶界上形成层状的β-Zr。晶界上的β-Zr在560℃热处理时发生了分解,得到颗粒状的β-Nb(100nm～200nm),但晶内棒状的β-Zr并不发生分解。变形使β-Zr变得更不稳定,促进其分解时的成核,可以得到粒径更小(10nm～60nm)的β-Nb第二相,原来不易发生分解的晶内棒状β-Zr,经变形处理后也可以发生分解。为了在含Nb的锆合金中获得细小并且均匀分布的β-Nb第二相,坯料经过均匀化β相加热淬火后,在后续的成材加工过程中,不应在高于610℃的温度下进行热处理,要避免重新形成块状的β-Zr。

The influence of the deformation and heat treatment on the decomposit ion of a-Zr in Zr-Sn-Nb alloys has been studied by means of transmission ele ctron microscopy (TEM). After fast cooling by heating the specimens at 750℃- 0 .5 h, some lumps of a-Zr are formed on grain boundaries and bar-like particle s of a-Zr are formed within grains. After faster cooling by heating the specim ens at 1 000℃- 0.5 h, a sandwich structure between thin layer a-Zr and lathy grains of á-Zr is formed. By aging the specimens at 560℃, the decomposition of a-Zr existing on the grain boundaries occurs to form particlelike a-Nb (1 00 nm～200 nm) , This does not occur for bar-like a-Zr existing within the g rains. Deformation can make the a-Zr more unstable and promotes the nucleation of fine particles of a-Nb (10 nm～60 nm) . The bar-like particles of a-Z r, which did not decompose only by aging at 560℃, can be decomposed by a defor mation-plus-aging heat treatment. In order to obtain a uniform dispersion and finer second phase particles of a-Nb in zirconium alloys containing niobium, t he material should not be heated over 610℃ to avoid reforming lumps of a-Zr o n grain boundaries during subsequent processing.