摘要
Ti Al合金是一种新型轻质耐高温金属结构材料,其优势在于低密度、高比强以及优异的高温性能。然而,由于Ti Al合金具有热加工窗口窄、高温变形能力不佳等问题,这导致合金构件成形困难。添加β稳定元素可以引入高温下无序的β相,显著增强合金的热变形能力,但元素对合金热变形行为的具体影响机制尚不明晰。基于此,以Ti-43Al-0.5Re-x Cr(x=1、1.5、2,原子分数,%)合金为研究对象,分别在1 150、1 200、1 250℃温度下热压缩。分析不同条件下的流变曲线,并研究温度及Cr含量对合金热变形组织及动态再结晶行为的影响,同时阐明了Ti-43Al-0.5Re-1.5Cr合金在1 200℃/0.01 s^(-1)热变形条件下的微观组织演变。结果表明,合金整体流变应力随温度和Cr含量的升高而降低。合金在1 150℃热变形,组织中存在大量残余片层团,主要发生片层团的弯曲扭折破碎,因此变形抗力较高;而在1 200和1 250℃热变形,合金组织大部分为高温无序α相,主要发生α相的连续动态再结晶,因此变形抗力低。随着Cr含量提高,高温下为BCC结构的β相含量提高,因此变形抗力降低。在1 200℃/0.01 s^(-1)/40%变形条件下,合金再结晶程度随β相含量提高而增加,因此Cr含量的增加会提高合金中β相的含量进而促进合金的动态再结晶过程。在Ti-43Al-0.5Re-1.5Cr合金1 200℃/0.01 s^(-1)/40%条件下的变形组织中发现细小β相周围分布有大量小角晶界,其相连形成大量小尺寸亚晶,因此形成更加细小的再结晶晶粒,β相起到了细化再结晶晶粒的作用。通过研究Ti-43Al-0.5Re-1.5Cr合金不同应变量条件下的微观组织,最终得出合金在1 200℃/0.01 s~(-1)热变形条件下的微观组织演变规律。
TiAl alloys,novel lightweight,high-temperature metal structural materials,feature low density,high specific strength,and excellent high-temperature performance.However,its narrow hot working window and poor deformation at high temperatures make the formation of alloy components difficult.Addingβ-stabilizing elements enhances hot deformation by introducing a disorderedβ-phase,but the mechanism is unclear.Therefore,Ti-43Al-0.5Re-xCr(x=1,1.5,2,at.%)alloys were used as the research objects,and thermal mechanical compression experiments were conducted at 1150,1200 and 1250℃.Flow curves under different conditions were analysed,the effects of temperature and Cr content on the thermal deformation microstructure and dynamic recrystallization were studied,and the microstructural evolution of the Ti-43Al-0.5Re-1.5Cr alloy at 1200℃/0.01 s^(-1) was clarified.The results indicate that the overall flow stress of the alloy decreases with increasing deformation temperature and Cr content.When the alloys are deformed at 1150℃,many residual lamellar colonies exist in the microstructure that primarily fragment through bending,twisting,and breaking leading to high deformation resistance. When the alloys are deformed at 1 200 or 1 250 ℃, most of the alloy microstructure is the α phase, which undergoes continuous dynamic recrystallization, resulting in low deformation resistance. Under deformation conditions of 1 200 ℃, a 0.01 s^(-1) strain rate, and 40% deformation, the degree of recrystallization in the alloy increases with increasing β phase content. Thus, an increase in the Cr content enhances the content of the β phase in the alloy, which promotes the dynamic recrystallization process of the alloy. In the deformed microstructure of the Ti-43Al- 0.5Re-1.5Cr alloy at 1 200 ℃, a strain rate of 0.01 s^(-1), and 40% deformation, many low angle grain boundaries (LAGBs, 2°~15° misorientation) are distributed around the fine β phases, which interconnect to form numerous small-sized subgrains, resulting in the formation of fine recrystallized grains. Thus, the β phase plays a role in refining the recrystallized grains.The microstructures of the Ti-43Al-0.5Re-1.5Cr alloy samples subjected to different strains were studied, revealing their microstructure evolution at 1 200 ℃/0.01 s^(-1) hot deformation.
作者
邵启航
楚玉东
陈晓飞
卫贝贝
马彪
唐斌
SHAO Qihang;CHU Yudong;CHEN Xiaofei;WEI Beibei;MA Biao;TANG Bin(State Key Laboratory of Solidification Processing,Northwestern Polytechnical University,Xi'an 710072,China;Sanhang Advanced Materials Research Institute Co.,Ltd.,Chongqing 401135,China)
出处
《铸造技术》
2025年第4期316-324,共9页
Foundry Technology
基金
国家重点研发计划(2021YFB3702605)。
关键词
TIAL合金
热变形
动态再结晶
CR含量
组织演变
流变曲线
TiAl alloy
thermal deformation
dynamic recrystallization
Cr content
microstructure evolution
flow curve
