摘要
对新型钴基高温合金Co-Al-V合金进行高温热压缩变形实验,实验变形温度为800 ℃～1 050 ℃,应变速率为0.001～1 s-1.实验结果表明在低温低应变速率(800℃,0.001 s-1)、较低温较高应变速率(950 ℃,0.1 s-1)和高温高应变速率(1 050 ℃,1 s-1)时,合金发生动态再结晶后出现孪晶,流变应力曲线也表现出达到峰值后先下降再上升的趋势,在变形温度为800℃和950 ℃时,高应变速率下更容易出现孪晶,随着应变速率降低,动态再结晶程度逐渐变高,在变形温度为1 050 ℃时,低应变速率下容易出现孪晶,随着应变速率的降低,动态再结晶程度逐渐降低.随着变形温度的升高,动态再结晶程度变高,再结晶晶粒尺寸逐渐变大.通过对EBSD测试结果分析,高温低应变速率(1050 ℃,0.001 s-1)条件下的再结晶晶粒尺寸相较于高温高应变速率(1 050 ℃,1 s-1)条件下的更大,高温下的孪晶界以Σ3边界为主,并且高温下应变速率越低,Σ3边界分数越高.为优化新型钴基高温合金的加工工艺提供理论依据.
Abstract
Thermal compression deformation experiments were conducted on a novel cobalt-based Co-Al-V superalloy.The deformation temperature was in the period of 800℃ and 1 050 ℃,and the strain rate varied from 0.001 to 1 s-1.The experimental results indicate that twins occurred after dynamic recrystallization of the alloy at low temperatures and low strain rates(800 ℃,0.001 s-1),at moderate temperatures and higher strain rates(950 ℃,0.1 s-1),as well as at higher temperatures and higher strain rates(1 050 ℃,1 s-1).The flow stress curves exhibited a trend of initially decreasing after reaching a peak,followed by an increase.At 800 ℃ and 950 ℃,twins were more easily formed under high strain rates.As the strain rate decreased,the degree of dynamic recrystallization gradually increased.At 1 050℃,twins were prone to formation at low strain rates,and the degree of dynamic recrystallization also de-creased as the strain rate decreased.With the increase of deformation temperature,the degree of dy-namic recrystallization increased,and the grain size of the recrystallized grains gradually became lar-ger.Analysis of the EBSD test results revealed that the grain size of the recrystallized grains under high-temperature and low strain rates(1 050 ℃,0.001 s-1)conditions was larger compared to that under high-temperature and high strain rates(1 050 ℃,1 s-1)conditions.The twin boundaries at high temperatures were majorly Σ3 boundaries,and the fraction of Σ3 bounda-ries increased with decreasing strain rate at high temperatures.These findings provide a theo-retical basis for optimizing the processing technology of the novel cobalt-based high-tempera-ture alloy.
维普
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