Effect of the Type of Loading on the Evolution of Microstructure and Crystallographic Texture in VT9 Titanium Alloy

Formation of crystallographic texture due to plastic deformation of cylindrical specimens of VT9 titanium alloy by uniaxial stretching, twisting, and simultaneous twisting and stretching is considered under the conditions of superplasticity. The dependence of the kind of loading on the type of texture formed and the grain size is considered. The uniformity of the variation of the texture in the cross section of specimens is studied as a function of the loading type.     

Mechanical Behavior and Evolution of the Lamellar Microstructure of Alloy VT9 as a Function of the Ratio of Axial and Shear Components of Hot Deformation

Results of a study of the effect of hot deformation under isothermal conditions under bicomponent (twisting + stretching) proportional loading with various ratios of the axial and shear components of the deformation on the mechanical behavior and evolution of the initial coarse lamellar microstructure and crystallographic texture in alloy VT9 are presented. It is shown that the ratio of the axial and shear components of the deformation is responsible for the degree of localization of plastic yield of the material and the fullness and intensity of transformation of the lamellar microstructure into a globular microcrystalline microstructure in the functional zone of deformed specimens.     

Effect of Thermomechanical Treatment on Functional Properties of Biodegradable Fe-30Mn-5Si Shape Memory Alloy

The structure, martensitic γ ↔ ε transformation temperatures, Young’s modulus, mechanical properties, and electrochemical behavior of Fe-30Mn-5Si (wt pct) biodegradable shape memory alloy subjected to various thermomechanical treatments (TMT) comprising hot rolling or cold rolling with post-deformation annealing were characterized by optical microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, differential scanning calorimetry, tensile testing, open circuit potential, and polarization curves measurements in Hanks’ solution, as compared to reference heat treatment. The optimum combination of mechanical properties (low Young’s modulus, high tensile strength, and appropriate ductility) for biomechanical compatibility was obtained after TMT with hot rolling at 600 and 800 °C due to the formation of favorable dynamically polygonized and recrystallized structures and decrease in the γ↔ε transformation starting temperature down to the human body temperature. The TMT did not show a significant effect on the corrosion rate as compared to the appropriate corrosion rate after the reference heat treatment. It is concluded that the TMT with hot rolling at 600 or 800 °C, which provides an optimum combination of the required corrosion rate in the simulation body fluid with high biomechanical compatibility, can be considered a promising treatment of Fe-30Mn-5Si biodegradable alloy for bone implants.

     

Effect of the Kind of Monotone Loading on the Transformation of Lamellar Microstructure Into a Microduplex One in Titanium Alloy VT9

The process of transformation of a lamellar microstructure into an equiaxial one in binary titanium alloys is determined not only by the temperature and rate conditions of the deformation but also by the kind of loading. The present work describes an experimental study of the effect of one- and two-component monotone loading on the microstructure and mechanical properties of binary titanium alloy VT9. It is shown that in two-component proportional loading the transformation of the lamellar microstructure occurs more uniformly over the cross section and the length of the specimens than under simple twisting or uniaxial stretching. Subsequent deformation by uniaxial stretching under optimum temperature and rate conditions of superplasticity is characterized by diminished yield stresses and completion of the process of transformation of the initial microstructure in the entire volume of the specimens.     

Effect of Initial Microstructure on the Mechanical Behavior and Evolution of Structure due to High-Temperature Stretching of VT9 Titanium Alloy

The effect of the initial structure of double-phase titanium alloy VT9 on the mechanical behavior and changes in the structure due to high-temperature uniaxial stretching is studied. Values of structural parameters after deformation are presented for six initial structural states of the alloy. The characteristics of uniform and lumped strain are computed. The effect of high-temperature annealing preceding the deformation on the ductility characteristics is described.     

Use of the effect of superplasticity to provide optimum properties in large parts made of biphase titanium alloys

Results of a complex study of the structure and properties of large disks (up to 500 mm in diameter and 70–80 mm high) made of alloy VT9 produced in a regime of superplasticity with the use of simple and complex loading are presented. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 2, pp. 36–39, February, 1999.