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tiger808

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[交流] 【讨论】固溶处理后枝晶消除，形成细小等轴晶粒，如何解释？请教高手！

各位大虾，我最进熔铸了一种有色合金，发现在铸态下形成了粗大的树枝晶，最大可达200微米，但是经过固溶处理后，枝晶熔断，形成了细小(晶粒尺寸不够均匀)的等轴晶，总体上晶粒尺寸要远小于铸态时的尺寸。这好像不合常理，下面附上铸态和固溶处理时的同倍数图片，欢迎讨论！

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1楼 2010-11-17 20:19:10

已阅回复此楼关注TA 给TA发消息送TA红花 TA的回帖

金教授

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小木虫(金币+0.5):给个红包，谢谢回帖交流
xucz(金币+2):鼓励参与讨论 2010-11-22 19:18:02
tiger808(金币+5):谢谢，忘记给金币了 2010-11-23 13:12:03

引用回帖:

Originally posted by tiger808 at 2010-11-17 20:19:10:
各位大虾，我最进熔铸了一种有色合金，发现在铸态下形成了粗大的树枝晶，最大可达200微米，但是经过固溶处理后，枝晶熔断，形成了细小(晶粒尺寸不够均匀)的等轴晶，总体上晶粒尺寸要远小于铸态时的尺寸。这好像不 ...

I have never touched Zn-25Al-2Cu alloy, but I know that in many Zn-Al alloys there is phase transformation induced grain refinement after homogenization. In that case, the grain refinement is due to phase transformation, rather than re-melting and/or recrystallization. The as-cast material is of single phase, i.e., super-saturated α’ phase. As shown in Figure 1, after homogenization and cooling down to room temperature, the α’ phase transforms into two phases: aluminum-rich α phase and zinc-rich η phase. The size of new phases is smaller, i.e., an initial α’ grain now contains several α grains and several η grains. The boundaries between α phase and η phase are high angle boundary type, but the boundaries between α/α grains and η /η grains may be low angle boundary type. To summarize, the phenomenon is actually a phase transformation, and the grain refinement observed is due to the nucleation and growth of new phases.

Figure 1. Phase transformation after homogenization. The solid lines indicate initial grain boundaries, and the dot lines indicate the phase boundaries and/or new grain boundaries.

I would like to suggest (i) do SEM element maps (aluminum map and zinc map) to see the spatial distribution of aluminum and zinc, and (ii) do an EBSD map to see the boundary angles (EBSD may also indicate different phases).

[ Last edited by 金教授 on 2010-11-22 at 14:40 ]