SUPERPLASTIC TENSILE BEHAVIOR OF A TI-Al-Mn ALLOY (original) (raw)
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Metals, 2018
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Metallurgical and Materials Transactions A, 2020
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Archives of materials science and engineering, 2007
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Materialwissenschaft und Werkstofftechnik
The present work aims at evaluating and understanding the mechanical behavior of a Ti-6Al-4 V alloy under hot and superplastic forming conditions. Tensile tests were performed at temperature range from 650 8C to 950 8C, at strain rates between 10-2 s-1 and 10-4 s-1. Three equiaxed microstructures, each characterized by a different starting grain size (4.9 mm, 3.0 mm and 0.5 mm), are compared to better understand the microstructural evolutions under hot and superplastic forming conditions and their influence on the mechanical behavior. Hence, an accurate model with microstructural considerations is proposed. The model capabilities consider the grain size evolution that is influenced by the temperature and deformation. The computed flow stresses strongly depend on the strain rate and on the considered initial grain size. Temperature and strain rate conditions may lead to a strain hardening phenomenon in some cases. The comparison between the model response and experiment shows a good agreement for all the tests carried out on Ti-6Al-4 V.
Transformation Superplasticity of Cast Titanium and Ti-6Al-4V
Metallurgical and Materials Transactions A, 2007
Samples of unalloyed titanium and Ti-6Al-4V with a cast, coarse-grain structure were subjected to simultaneous mechanical loading and thermal cycling about their transformation range to assess their capability for transformation superplasticity. Under uniaxial tensile loading, high elongations to failure (511 pct for titanium, and 265 pct for Ti-6Al-4V) and an average strainrate sensitivity exponent of unity are observed. Samples previously deformed superplastically to a strain of 100 pct show no significant degradation in room-temperature mechanical properties as compared to the undeformed state. Biaxial dome bulging tests confirm that transformation superplasticity is activated under thermal cycling and faster than creep deformation. The cast, coarse-grained titanium and Ti-6Al-4V have similar transformation-superplasticity characteristics as wrought or powder-metallurgy materials with finer grains. This may enable superplastic forming of titanium objects directly after the casting step, thus bypassing the complicated and costly thermomechanical processing steps needed to achieve fine-grain superplasticity.