U基二元熔体的热力学计算

β-Grain Growth and Influence of Its Grain Size on Damage-Tolerance Property in Titanium Alloy

摘要:

分别对a+b 两相区及b单相区锻造的TC4合金在相变点以上温度保温，然后对不同温度条件下原始b晶粒尺寸进行统计，并测试了几种不同晶粒尺寸下的疲劳裂纹扩展速率及断裂韧性。晶粒尺寸统计结果显示：原始b晶粒尺寸不仅与热处理温度和时间有关，也与锻造工艺有关。原始b晶粒尺寸与保温时间呈指数关系；在1 h条件下原始b晶粒尺寸并不总是随温度的升高一直增大，在某个温度范围内有一极值；锻造工艺不同，原始b晶粒尺寸波动也不同。从晶粒生长的热力学及动力学两方面对上述现象进行了分析。力学性能结果显示晶粒尺寸对裂纹扩展速率及断裂韧性均有影响，并对影响机理进行了分析。

Abstract:

The purpose of the present study is to know the influences of thermo-mechanical processing and heat-treatment on the prior b-grain size of TC4 titanium alloy, and the influence of grain size on damage-tolerance properties is also discussed. The average b-grain sizes under different thermo-mechanical processing and solution treatment conditions were measured. Noticeable difference of b-grain growth behavior was found between α+b forged and b forged TC4 alloy under the same heat-treatment conditions. The exponential relationship between b-grain size and solution time was presented. The results show that b-grain size does not always increase with increasing of solution-treatment temperature; a limit value of the grain size will appear in certain temperature region. For different forging process, the fluctuation of the prior b -grain size is different. This phenomenon is discussed in terms of grain growth thermodynamics and kinetics laws. Damage-tolerance properties results show that grain size has noticeable influence on fatigue crack growth rate and fracture toughness property.