Abstract
Abstract Here we analyze the microstructure and phase composition of a Ti alloy with 0.16Pd and 0.14Fe (wt%) alloy exposed to warm equal channel angular pressing (ECAP) at 648 K. The analysis shows that after four ECAP passes, the material assumes a submicrocrystalline structure with an average grain size of 0.28 μm, as against its initial value 10 μm, and that the α phase dominates in the alloy both before and after ECAP. The initial alloy reveals a high content of Fe and Pd atoms near grain boundaries compared to central grain regions. Such near-boundary zones contain orthorhombic α′′ martensite in addition to the α phase, and β or α + β particles are found directly at the grain boundaries. These features of the phase composition are inherited after ECAP. The yield strength of the ECAP treated alloy is 500 MPa, being greater than the initial strength 350 MPa, and its margin of plasticity is rather high. The torsional strain up to fracture in the initial and in the ECAP treated alloy is 70% and 50%, respectively.
Highlights
Titanium and its alloys hold the lead in medicine over other metal materials [1,2,3] due to their high strength, high corrosion resistance, and biocompatibility
The analysis shows that after four equal channel angular pressing (ECAP) passes, the material assumes a submicrocrystalline structure with an average grain size of 0.28 μm, as against its initial value 10 μm, and that the α phase dominates in the alloy both before and after ECAP
We are aware of only one paper [13] which reports on the structure and properties of an ECAP treated alloy of grade 7 (Ti–0.14Pd–0.03Fe, wt%), showing that two ECAP passes with a channel angle of 105∘ at 673 K provide a microcrystalline structure with a grain size of ~3.8 μm in the material and improve its corrosion resistance compared to the initial coarse-grained state
Summary
Titanium and its alloys hold the lead in medicine over other metal materials [1,2,3] due to their high strength, high corrosion resistance, and biocompatibility. Research data show that Ti alloys with a small Pd content are highly resistant to corrosion even in saline solutions with fluorine compounds, which greatly speed up the corrosion of other Ti alloys used in medicine [6] Such Ti–Pd alloys are produced in different countries of the world (USA, Great Britain, Russia, Japan, China, etc.) as they serve to produce devices and constructions for operation with chemically active media [4, 7], and their use is expected in shipbuilding [8] and in manufacturing storage containers for high-level nuclear waste [9]. Technologies of severe plastic deformation are available allowing the formation of a submicro- or a nanocrystalline structure in metals and alloys as well as improvement of their mechanical properties [10,11,12] Among these technologies is the equal channel angular pressing (ECAP). We present research data on the structure, phase state, and mechanical properties of a Ti alloy containing 0.16Pd and 0.14Fe wt% after equal channel angular pressing with a channel angle of 90∘ at 648 K
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