鎳基高溫合金定向凝固過程中的匯聚型雙晶競爭生長
發布人：上海艾荔艾合金股份有限公司www.shailiai.cn
更新時間：2016-05-10
采用籽晶法控制晶體取向, 研究了不同抽拉速率下鎳基高溫合金匯聚型雙晶的競爭生長.
鎳基高溫合金定向凝固過程中的匯聚型雙晶競爭生長CONVERGING COMPETITIVE GROWTH IN BI-CRYSTAL OF?Ni-BASED SUPERALLOY DURING DIRECTIONAL?SOLIDIFICATION采用籽晶法控制晶體取向, 研究了不同抽拉速率下鎳基高溫合金匯聚型雙晶的競爭生長. 結果表明, 低抽拉速率下, 非擇優枝晶能夠穿插進入擇優枝晶間的液相通道, 抑制擇優枝晶的生長, 使晶界向擇優晶粒方向偏移. 高抽拉速率下, 非擇優枝晶幾乎全部被晶界擇優枝晶阻擋, 晶界與擇優枝晶干平行. 非擇優枝晶進入擇優枝晶間的液相通道使擇優枝晶萎縮消失是非擇優晶粒淘汰擇優晶粒的主要因素, 并以此提出了抽拉速率對競爭生長的影響機制.?
Ni-based single crystal superalloy has been widely used in turbine blades owing to its excellent high?temperature mechanical behavior. In order to completely exhibitits high temperature mechanical properties, the?seed method has been used to produce Ni-based single crystal components for [001] orientation paralleling to?main force direction. Stray crystals, which unexpectedly nucleate in the melt-back region, will competitive grow?with seed during directional solidification. It is important to profoundly understand the mechanism of competitive?growth for finding ways to overgrow stray crystal during producing Ni-based single crystal components. However,?within the published research there are conflicting views on the mechanism of competitive growth at converging?case. Using seed technology, bi-crystal converging competitive growth was investigated with different pulling?rates. A series of polishing and imaging quenching interface were done for the positional relationship of dendrites?near grain boundary in 3D reference. It was found that solidification microstructures were different with different?crystal orientations. Unfavorable orientated dendrite tilting to heat flux restrained favorable orientated dendrite?aligning to heat flux mainly thought inserting into the favorable orientated dendrites channel, and this resulted in?unfavorable orientated dendrite growth over growing favorable orientated dendrite at low pulling rate. However,?at high pulling rate the unfavorable dendrites mainly blocked by grain boundary favorable dendrite and the grain?boundary grew paralleling to favorable orientated dendrite core. Favorable orientated dendrite depressing and?vanishing, owning to that unfavorable orientated dendrite inserting into favorable orientated dendrites channel?result in adjusting primary dendrite spacing, is the main factor to favorable orientated grain overgrew by?unfavorable orientated grain. According to above mechanism, effect of pulling rate on competitive growth at?converging case was interpreted. This could broaden our understanding of competitive growth at converging case?in 3D reference.?
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