Microstructural mechanisms during hot working of commercial grade Ti-6Al-4V with lamellar starting structure

被引：358

作者：

Seshacharyulu, T ^{[1
]}

Medeiros, SC ^{[1
]}

Frazier, WG ^{[1
]}

Prasad, YVRK ^{[1
]}

机构：

[1] USAF, Res Lab, MLMR, Mat Proc Design Branch,Mat & Mfg Directorate, Wright Patterson AFB, OH 45433 USA

来源：

MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING | 2002年 / 325卷 / 1-2期

关键词：

microstructural mechanisms; Ti-6Al-4V; lamellar starting structure;

D O I：

10.1016/S0921-5093(01)01448-4

中图分类号：

TB3 [工程材料学];

学科分类号：

0805 ; 080502 ;

摘要：

The hot deformation behavior of commercial grade Ti-6Al-4V with a lamellar starting microstructure is studied in the temperature range 750-1100 degreesC and strain rate range 3 x 10(-4) -10 s(-1) with a view to model the microstructural evolution. On the basis of flow stress data obtained as a function of temperature and strain rate in compression, a processing map for hot working has been developed. In the ranges 800-975 degreesC and 3 x 10(-4) -10(-2) s(-1), globularization of lamellae occurs for which an apparent activation energy of 455 kJ mol(-1) has been estimated using the kinetic rate equation. Stress-dependent thermal activation analyses proposed by Schock and Cocks et al. have shown that the apparent activation energies are in the range 160-245 kJ mol(-1) and the normalized activation volumes are in the range 20-80, which suggest that cross-slip is the rate controlling process during globularization. The variation of primary alpha grain size with Zener-Hollomon parameter (Z) in the globularization region exhibited a linear relationship on a log-log scale. At strain rates slower than 10(-1) s(-1) and temperatures below 900 degreesC, cracking at the prior beta grain boundaries/triple junctions occurs, which sets the lower limits for globularization. At strain rates higher than 10(-1) s(-1) in the alpha + beta range, the material exhibited flow instabilities manifested as adiabatic shear bands. These bands are intense below 800 degreesC and above 1 s(-1) and caused cracking along the bands, In the beta phase field, dynamic recrystallization (DRX) occurs at about 1100 degreesC and in the strain rate range 10(-3) -10(-1) s(-1). The apparent activation energy for DRX of beta is about 172 kJ mol(-1) which is close to that for self-diffusion in beta phase (153 kJ mol(-1)). The application of these results in the design of bulk metalworking processes for achieving microstructural control is discussed. Published by Elsevier Science B.V.

引用

页码：112 / 125

页数：14

共 21 条

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