Abstract
Beta phase stabilizing elements such as Mo have strong tendency to segregate. We have introduced swirly type segregation of Mo in Ti-12Mo (mass %) alloy through groove bar rolling. After solution treatment and low temperature aging, hard omega phase was precipitated heterogeneously, which improved the room temperature tensile elongation values without sacrificing tensile strength. In this study, the effect of Mo segregation and heterogeneous distribution of omega phase on Charpy absorbed energy was investigated in Ti-12Mo alloy. Samples with two types of segregation were prepared; namely, swirly segregation in bar rolled sample and layered segregation in plate rolled sample. For comparison, we have also prepared Ti-12Mo bar samples with lesser Mo segregation, through high temperature thermomechanical treatment. Charpy impact tests were carried out at room temperature, 373 K and 473 K, respectively, using the samples after aging to introduce isothermal omega-phase. The samples with the segregation exhibited higher Charpy absorbed energy, especially at higher temperature of 473 K, while the sample with the swirly segregation showed higher Charpy absorbed energy than that with the layered segregation. The sample with lesser Mo segregation exhibited brittle intergranular fracture surface after Charpy testing. On the contrary, samples with Mo segregation exhibited ductile transgranular fracture surfaces.
Highlights
Beta-type Ti-Mo alloys are promising material for off-shore structure and bio-medical applications with their superior corrosion resistance [1]
We have investigated the effect of Mo segregation and heterogeneous distribution of omega phase on Charpy absorbed energy in Ti-12Mo alloy
crucible levitation melting (CCLM) ingots were forged to 40 mm square slabs at higher temperature of 1473 K, rolled to 17.5 mm square bars at 1473 K, and heat treated at 1473 K for 10.8 ks to reduce the segregation
Summary
Beta-type Ti-Mo alloys are promising material for off-shore structure and bio-medical applications with their superior corrosion resistance [1]. We have been trying to control this segregation structure for property enhancement of Ti-Mo alloys, and have successfully introduced swirly segregation of Mo in Ti-12Mo (mass %) alloy through groove bar rolling [3, 4]. After solution treatment and low temperature aging, hard second phase (omega phase) was precipitated heterogeneously, which improved the room temperature tensile elongation values without sacrifice of tensile strength [3, 4]. We have investigated the effect of Mo segregation and heterogeneous distribution of omega phase on Charpy absorbed energy in Ti-12Mo alloy
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