应力对Al-Zn-Cu系平衡相的影响

Effect of stress on equilibrium phases in Al-Zn-Cu alloys

采用99.999%分析纯的Al、Zn、Cu作原料,在外热式坩埚炉中熔制了5Cu40Zn55Al、15Cu20Zn65Al和3Cu17Zn80Al共3种合金,将其经过成分均匀化处理后,对包含亚稳相的3种合金分别进行球磨和手工锤击实验,采用X射线衍射仪分析合金平衡相组合。结果表明:合金通过球磨能得到室温平衡相,而通过手工捶击则得不到室温平衡相;能否通过应力诱发相变快速获得室温合金平衡相组织与合金应力作用产生的变形机制有关;球磨能使合金内部发生大量变形,为合金向平衡相转变提供驱动力和原子扩散通道;而手工锤击主要是使合金发生以解理为主的脆性断裂,这种变形不能为亚稳相的转变提供必要的驱动力和原子扩散通道,从而得不到合金室温下的平衡相组成。

5Cu40Zn55Al, 15Cu20Zn65Al and 3Cul7Zn80Al alloys were founded by using 99.999% Al, Zn and Cu as raw mater material in external-heat crucible. After uniform treatment, the alloys were then treated, respectively, by hand hammering and ball milling. The equilibrium phases of Al-Zn-Cu alloys were analyzed by XRD. The results show that the equilibrium phases of these three alloys can be obtained by ball milling at room temperature, but the result is contrary by hand hammering. So it is obtained that whether the equilibrium phase can be obtain or not by the stress at room temperature mainly depends on the feature of deformation mechanism of the alloys. During ball milling, the stress provides adequate deformation in the inner structure, which supplies enough driving force and diffuse alleyway of atom for the transformation of metastable phase. But the stress in the experiment during hand hammering only cause brittle rupture from cleavage to oriented, this can not offer enough driving force and diffuse alleyway of atom for the transformation of metastable phase, so the equilibrium phase of alloy can not be gotten at room temperature.