Studies on Ductile Damage and Flow Instabilities during Hot Deformation of a Multiphase γ-TiAl Alloy

2014 ◽  
Vol 611-612 ◽  
pp. 99-105 ◽  
Author(s):  
Dilek Halici ◽  
Hassan Adrian Zamani ◽  
Daniel Prodinger ◽  
Cecilia Poletti ◽  
Daniel Huber ◽  
...  
Keyword(s):  
Hot Deformation ◽  
Titanium Aluminide ◽  
Titanium Aluminides ◽  
Turbine Blades ◽  
Shear Bands ◽  
Flow Instabilities ◽  
Ductile Damage ◽  
Gamma Titanium Aluminide ◽  
Gamma Titanium ◽  
Damage Models

Gamma titanium aluminides are promising alloys for low-pressure turbine blades. A significant disadvantage of such intermetallic alloys is failure induced during forming processes due to ductile damage and flow instabilities. Previous investigations on a gamma titanium aluminide alloy (TNM), have shown ductile damage due to tensile stress components and instabilities such as shear bands, pores and micro-cracks at low temperatures and high strain rates. The main part of the current work is to delineate damage and unstable regions in the low temperature region. Hot deformation experiments are conducted on a Gleeble®3800 thermomechanical treatment simulator to obtain flow curves to be implemented in a finite element method (FEM) code. Instabilities in the material are described by existing instability criteria as proposed by Semiatin and Jonas and implemented into FEM code DEFORMTM 2D. Predictions of ductile damage models and the instability parameter are validated through detailed microstructural studies of deformed specimens analysed by light optical- and scanning electron microscopy.

Modelling of the Ductile Damage Behaviour of a Beta Solidifying Gamma Titanium Aluminide Alloy during Hot-Working

2014 ◽  
Vol 783-786 ◽  
pp. 556-561 ◽  
Author(s):  
Dilek Halici ◽  
Daniel Prodinger ◽  
Cecilia Poletti ◽  
Daniel Huber ◽  
Martin Stockinger ◽  
...  
Keyword(s):  
Titanium Aluminide ◽  
Titanium Aluminides ◽  
Hydrostatic Stress ◽  
Effective Strain ◽  
Maximum Principal Stress ◽  
Ductile Damage ◽  
Hot Workability ◽  
Gamma Titanium Aluminide ◽  
Gamma Titanium ◽  
Damage Criteria

Gamma titanium aluminides are innovative materials for high temperature and light weight applications [1]. On the other hand, their hot workability can be limited by failure during hot deformation processes. The prediction of ductile damage in metallic materials can be performed by macromechanical ductile damage criteria [2-4]. If the calculated damage D parameter exceeds a critical value Dc, the material fails. Some macromechanical ductile damage criteria are shown in Table 1, with σ as effective stress, ε as effective strain, σmax as maximum principal stress, σm as hydrostatic stress (mean stress) and εf as equivalent fracture strain. The damage responds to strain localization and thus, to multiaxial stress concentration that increases fracture probability.

The Dependence of Tensile Ductility on Investment Casting Parameters in Gamma Titanium Aluminides

1998 ◽  
Vol 552 ◽  
Author(s):  
R. Raban ◽  
L. L. ◽  
T. M.
Keyword(s):  
Titanium Aluminide ◽  
Titanium Aluminides ◽  
Tensile Ductility ◽  
Gamma Titanium Aluminide ◽  
Cooling Rates ◽  
Gamma Titanium ◽  
Investment Cast ◽  
Thermal Data ◽  
Titanium Aluminide Alloys ◽  
Simulation Package

ABSTRACTPlates of three gamma titanium aluminide alloys have been investment cast with a wide variety of casting conditions designed to influence cooling rates. These alloys include Ti-48Al-2Cr-2Nb, Ti- 47Al-2Cr-2Nb+0.5at%B and Ti-45Al-2Cr-2Nb+0.9at%B. Cooling rates have been estimated with the use of thermal data from casting experiments, along with the UES ProCAST simulation package. Variations in cooling rate significantly influenced the microstructure and tensile properties of all three alloys.

Comparison of the electrochemical machinability of electron beam melted and casted gamma titanium aluminide TNB-V5

2017 ◽  
Vol 232 (4) ◽  
pp. 586-592 ◽  
Author(s):  
Fritz Klocke ◽  
Tim Herrig ◽  
Markus Zeis ◽  
Andreas Klink
Keyword(s):  
Surface Roughness ◽  
Electron Beam ◽  
Current Density ◽  
Titanium Aluminide ◽  
Titanium Aluminides ◽  
Electrochemical Machining ◽  
Dissolution Behavior ◽  
Removal Rates ◽  
Gamma Titanium Aluminide ◽  
Gamma Titanium

Additive manufacturing technologies are becoming more and more important for the implementation of efficient process chains. Due to the possibility of a near net shape, manufacturing time for finish-machining can significantly be reduced. Especially for conventionally hard to machine materials like gamma titanium aluminides (γ-TiAl), this manufacturing process is very attractive. Nevertheless, for most applications, a rework of these generative components is necessary. Independently of the mechanical material properties, electrochemical machining is one promising technology of machining these materials. Major advantages of electrochemical machining are its process-specific characteristics of high material removal rates in combination with almost no tool wear. But electrochemical machining results are highly dependent on the microstructure of the material regarding the surface roughness. Therefore, this article deals with research on electrochemical machining of electron beam melted γ-TiAl TNB-V5 compared to a casted form of this alloy. The difference between the specific removal rates as a function of current density is investigated using electrolytes based on sodium nitrate and sodium chloride. Moreover, the dissolving behavior of the electron beam melted and casted structure is analyzed by potentiostatic polarization curves. The surface roughness is heavily dependent on a homogeneous dissolution behavior of the microstructure. Thus, the mean roughness as a function of current density is investigated as well as rim zone analyses of the different structures.

scholarly journals Surface Quality of Amilled Gamma Titaniumaluminide for Aeronautical Applications

2014 ◽  
Vol 5 (2) ◽  
pp. 60-65
Author(s):  
Grzegorz Radkowski ◽  
Jaroslaw Sep
Keyword(s):  
High Pressure ◽  
Titanium Aluminide ◽  
Titanium Aluminides ◽  
Turbine Blades ◽  
Low Pressure ◽  
Aviation Industry ◽  
Gamma Titanium ◽  
Low Pressure Turbine ◽  
High Pressure Compressor ◽  
Pressure Compressor

Abstract Gamma titanium aluminides are an interesting alternative for nickel, iron or cobalt matrix superalloys. Due to the advantageous strength properties at high temperatures they can successfully replace superalloys in applications such as high pressure compressor blades, low pressure turbine blades, high pressure compressor case, low pressure turbine case. Milling is one of the processes that can be applied in the forming elements made from this type of alloys for the aviation industry. Research included the selection of tool, the process kinematics and the range of milling gamma titanium aluminide (Ti-45Al-5Nb-0.2B-0.2C) process parameters were carried out. Milling can be an effective method of forming of elements made of gamma TiAL in the range of processing parameters: vc = 20-70 m/min, ap = 0.3-0.7 mm, fz = 0.1- 0.45 mm/tooth. In the tests carried out the best results were obtained using a R300-016A20L- 08L milling cutter, S30T tool coating and in-cut milling.

Limitations of an Indentation Model for Grinding Gamma Titanium Aluminide

2002 ◽  
Author(s):  
H. Ali Razavi ◽  
Steven Danyluk ◽  
Thomas R. Kurfess
Keyword(s):  
Force Control ◽  
Titanium Aluminide ◽  
Normal Force ◽  
Removal Rate ◽  
Cubic Boron Nitride ◽  
Normal Component ◽  
Grinding Force ◽  
Cutting Depth ◽  
Gamma Titanium Aluminide ◽  
Gamma Titanium

This paper explores the limitations of a previously reported indentation model that correlated the depth of plastic deformation and the normal component of the grinding force. The indentation model for grinding is studied using force control grinding of gamma titanium aluminide (TiAl-γ). Reciprocating surface grinding is carried out for a range of normal force 15–90 N, a cutting depth of 20–40 μm and removal rate of 1–9 mm3/sec using diamond, cubic boron nitride (CBN) and aluminum oxide (Al2O3) abrasives. The experimental data show that the indentation model for grinding is a valid approximation when the normal component of grinding force exceeds some value that is abrasive dependent.

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