Coupling Effects of Melt Treatment and Ultrasonic Treatment on Solidifying Microstructure and Mechanical Performance of Ti44Al6Nb1Cr Alloy
Coupling Effects of Melt Treatment and Ultrasonic Treatment on Solidifying Microstructure and Mechanical Performance of Ti44Al6Nb1Cr Alloy
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DOI：
10.1007/s11661-017-4425-y
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发表时间：
2018-02
期刊：
影响因子：
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通讯作者：
Zheng Deshuang;Chen Ruirun;Ma Tengfei;Ding Hongsheng;S. Yanqing;G. Jingjie;F. Hengzhi
中科院分区：
文献类型：
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作者：
Zheng Deshuang;Chen Ruirun;Ma Tengfei;Ding Hongsheng;S. Yanqing;G. Jingjie;F. Hengzhi
研究了熔体处理与超声处理耦合对Ti44 Al 6 Nb 1Cr合金凝固组织和力学性能的影响。在熔体处理过程中，较低的结晶度有利于组织细化，片层团尺寸从512 μm减小到243μm;而较低的冷却速度则导致组织粗化，片层团尺寸从458 μ m增大到615μm。超声耦合处理后，在适度的退火度和冷却速度下，原始粗大片层团尺寸明显细化至56和38μm，抗压强度分别提高了60.71%和47.89%，压缩应变分别增大了80.19%和112.33%。结果表明，熔体温度对超声波细化效果有决定性影响，在结晶温度附近存在一个最佳温度范围：温度过高会导致晶核重熔，影响细化效果;温度过低会导致熔体粘度过高，影响超声波细化效果。超声波作用下，熔体过冷度增加，成分过冷区扩大，晶体形核扩大;溶质富集增强，形成具有较高溶液浓度梯度的准稳态，晶体生长速度提高。
The coupling effects of melt treatment and ultrasonic treatment on the solidifying microstructure and mechanical performance of Ti44Al6Nb1Cr alloy are investigated. During melt treatment, a low superheat degree is beneficial for microstructure refinement, with the lamellar colony size decreasing from 512 to 243μm, while a low cooling rate leads to the microstructure coarsening as the lamellar colony size enlarges from 458 to 615μm. After coupling with ultrasonic treatment, under moderate superheat degree and cooling rate, the original coarse lamellar colony size is significantly refined to 56 and 38μm, the compressive strength is improved by 60.71 and 47.89 pct, and the compressive strain is enlarged by 80.19 and 112.33 pct, respectively. It is found that the ultrasonic refining efficiency is dominated by the melt temperature, and there is an optimum temperature range near the crystallization temperature: a too-high temperature leads to the remelting of crystal nuclei, impairing the refining efficiency, whereas a too-low temperature results in high viscosity, hindering the ultrasonic effects. Under ultrasonic treatment, the melt supercooling is increased, leading to an extended constitutional supercooling region, which will enlarge the crystal nucleation; the solute enrichment is enhanced, forming a quasi-steady state with a higher solution concentration gradient, which improves the crystal growth velocity.