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

DSpace at IIT Bombay

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Title WELD HEAT-AFFECTED ZONE IN TI-6AL-4V ALLOY .2. MODELING AND EXPERIMENTAL SIMULATION OF GROWTH AND PHASE-TRANSFORMATIONS
 
Creator SHAH, AK
KULKARNI, SD
GOPINATHAN, V
KRISHNAN, R
 
Subject grain-growth
microstructure
diagrams
ti-6al-4v alloy
heat-affected zone
computer modeling
experimental simulation
grain growth
phase transformation
thermal response
hardness values
fracture toughness
kinetic strength
 
Description The thermal response of materials to a welding heat source sometimes causes metallurgical and mechanical problems, e.g., residual stresses and distortion and changes in mechanical properties due to changes in the microstructure. Experimental resting is one way to approach a solution. However, experiments alone cannot separate the factors involved and their integrated effects on the complex behavior of the material subject to the welding heat. Mathematical modeling simulates the welding behavior according to the physical laws. Therefore, quantitative or qualitative changes of thermal response of material, depending on the complexity of the model, can be traced in a mathematical formulation. The amount of experimental effort can be minimized. The mathematical models can also be used to explain the observed phenomena in the experimental tests. The work carried out involved development of theoretical models to predict the alpha + beta double right arrow beta transformation during heating, grain growth, and subsequent transformation of beta on cooling in the Ti-6-Al-4V alloy. The data for correlation of microstructure to mechanical properties have been generated experimentally using simulated HAZ (heat-affected zone) specimens. The overall effect of the weld variables on the HAZ microstructure can be visualized from the HAZ microstructure diagram which depicts various phase transformations occurring during the weld thermal cycle in t(8/5)-T-p space. The 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 can 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) parameter. The experimental simulation results confirm excessive grain growth in the near-HAZ region. The hardness values do not show any significant trend, but the fracture toughness is found to deteriorate in the HAZ.
 
Publisher AMER WELDING SOC
 
Date 2011-07-17T10:17:45Z
2011-12-26T12:50:15Z
2011-12-27T05:36:24Z
2011-07-17T10:17:45Z
2011-12-26T12:50:15Z
2011-12-27T05:36:24Z
1995
 
Type Article
 
Identifier WELDING JOURNAL, 74(10), S325-S338
0043-2296
http://dspace.library.iitb.ac.in/xmlui/handle/10054/4697
http://hdl.handle.net/10054/4697
 
Language en