WELD HEAT-AFFECTED ZONE IN TI-6AL-4V ALLOY .2. MODELING AND EXPERIMENTAL SIMULATION OF GROWTH AND PHASE-TRANSFORMATIONS

Citation
Ak. Shah et al., WELD HEAT-AFFECTED ZONE IN TI-6AL-4V ALLOY .2. MODELING AND EXPERIMENTAL SIMULATION OF GROWTH AND PHASE-TRANSFORMATIONS, Welding journal, 74(10), 1995, pp. 325-338
Citations number
44
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Metallurgy & Metallurigical Engineering
Journal title
ISSN journal
0043-2296
Volume
74
Issue
10
Year of publication
1995
Pages
325 - 338
Database
ISI
SICI code
0043-2296(1995)74:10<325:WHZITA>2.0.ZU;2-0
Abstract
The thermal response of materials to a welding heat source sometimes c auses metallurgical and mechanical problems, e.g., residual stresses a nd distortion and changes in mechanical properties due to changes in t he microstructure. Experimental resting is one way to approach a solut ion. However, experiments alone cannot separate the factors involved a nd their integrated effects on the complex behavior of the material su bject to the welding heat. Mathematical modeling simulates the welding behavior according to the physical laws. Therefore, quantitative or q ualitative changes of thermal response of material, depending on the c omplexity of the model, can be traced in a mathematical formulation. T he amount of experimental effort can be minimized. The mathematical mo dels can also be used to explain the observed phenomena in the experim ental tests. The work carried out involved development of theoretical models to predict the alpha + beta double right arrow beta transformat ion during heating, grain growth, and subsequent transformation of bet a on cooling in the Ti-6-Al-4V alloy. The data for correlation of micr ostructure to mechanical properties have been generated experimentally using simulated HAZ (heat-affected zone) specimens. The overall effec t of the weld variables on the HAZ microstructure can be visualized fr om the HAZ microstructure diagram which depicts various phase transfor mations occurring during the weld thermal cycle in t(8/5)-T-p space. T he results of computer modeling indicate that due to the rapid heating and cooling cycles encountered in welding, the shift in beta transus may be hundreds of degrees. Also, in the near-HAZ region, the grains c an grow an order of magnitude larger than the original grain size. The formation of lamellar a can be minimized by reducing the t(8/5) param eter. The experimental simulation results confirm excessive grain grow th in the near-HAZ region. The hardness values do not show any signifi cant trend, but the fracture toughness is found to deteriorate in the HAZ.