以Ti-43Al-3Si为籽晶, 在Ti-47Al合金中成功的制备出了与生长方向平行的定向全片层组织. 结合Ti-Al二元相图, 分析了亚包晶和过包晶成分合金的凝固路径, 确定了籽晶法控制TiAl合金片层方向对母料合金成分的要求. 通过对不同生长速率下Ti-47Al合金籽晶法定向凝固组织的观察发现, 成功的引晶生长应保证高温相沿非择优取向<11-20>以平界面生长, 即采用足够高的温度梯度和足够低的生长速率. 相胞状树枝晶生长过程中将在枝晶间析出相, 破坏定向全片层组织.
By using a seed crystal, the TiAl/Ti3Al lamellar orientation was aligned parallel to the growth direction in directionally solidified Ti-47Al alloys. The solidification behavior of hypo-peritectic and hyper-peritectic alloys in TiAl equilibrium phase diagram was studied, and the composition range of successful seeding of TiAl alloys was also determined. Through the lamellar microstructure examination of Ti-47Al alloys directionally solidified from Ti-43Al-3Si seed under the conditions of different growth rates, it was found that a successful seeding requires that the solid/liquid interface must be planer during solidification. This can be achieved by growing crystals at a sufficiently high thermal gradient in the liquid and at a sufficiently low growth rate. It showed that the seeding process easily failed if cells or dendrites formatted, new grains would nucleated or α grains with a preferred growth orientation of <0001> would protrude to the liquid, then the lamellar direction was changed.
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