基于LAM全域分析技术探究GH4698热加工过程组织演化

Microstructure Evolution of GH4698 during Thermal Processing Based on LAM Universe Analysis Technique

目的研究GH4698在变形温度为1100℃、压下速率为0.12 mm/s、压下量为40%的热变形条件和固溶温度为1120℃、保温时间为8 h、水淬的热处理条件下的显微组织演化规律。方法采用Thermecmastor-z型热模拟试验机进行等温恒应变速率压缩试验,并随后在热处理炉内完成热处理试验,利用大面积拼接(LAM)全域表征技术,分析GH4698热变形和固溶处理后显微组织的演化规律。结果在应变量小于动态再结晶临界应变(ε=0.165)的区域,固溶后晶粒尺寸分布不均,平均晶粒尺寸为63μm,最大晶粒尺寸为439μm,超过平均晶粒尺寸的5倍以上;随着应变量的增大(ε>0.165),动态再结晶百分数随之增加,固溶后平均晶粒尺寸也呈减小趋势。热变形后孪晶分布与应变量密切相关,具体为小应变区孪晶密度为40.7%,中应变区孪晶密度为10.6%,大应变区孪晶密度为28.9%。结论固溶后晶粒尺寸分布特征与热变形后动态再结晶百分数密切相关:由于变形储能分布不均,固溶后晶界迁移速率较大,导致在临界应变区(ε=0.165)晶粒尺寸分布不均;固溶后小于临界应变的区域(ε<0.165),主要发生静态再结晶使晶粒细化;随着动态再结晶百分数的增加,固溶后晶粒尺寸随着应变量(ε>0.165)的增大而逐渐减小。孪晶分布和动态再结晶也存在一定的相关性。

The work aims to study the microstructure evolution of GH4698 that is deformed at 1100℃with 0.12 mm/s reduction rate to the height reduction of 40%and is treated by water quenching at 1120℃for 8 h.The isothermal constant strain rate compression experiment was carried out by Thermecmastor-z thermal simulation testing machine,and then the heat treatment experiment was completed in the heat treatment furnace.The microstructure evolution law of GH4698 after hot deformation and solution treatment was analyzed by using Large Area Montages(LAM)global characterization technology.In the region where the strain was less than the critical strain of dynamic recrystallization(ε=0.165),the average grain size was 63μm when the maximum grain size was 439μm,which meant that the maximum grain size was more than five times as much as the average grain size and the grain size distribution was not uniform after solution treatment.The percentage of dynamic recrystallization increased with the increase of strain(ε>0.165)and the average grain size decreased after solution treatment.The distribution of twins after hot deformation was closely related to the strain,which was 40.7%in the small strain region,10.6%in the medium strain region and 28.9%in the large strain region.The characteristics of grain size distribution after solution are closely related to the percentage of dynamic recrystallization after hot deformation.Due to the uneven distribution of the stored energy of hot deformation,the grain boundary migration rate is larger after solution treatment,the grain size in the critical strain region(ε=0.165)is distributed unevenly.In the region where the strain is less than the critical strain after solution treatment(ε<0.165),static recrystallization mainly occurs to refine the grains;with the increase of dynamic recrystallization percentage,the grain size decreases with the increase of strain(ε>0.165).In addition,there is also a certain correlation between the distribution of twins and the dynamic recrystallization.