Influence of Cr content on phase constitution, electrical resistivity and vickers hardness in quenched Ti-Cr alloys

Abstract

As basic study to develop low cost b Ti alloys, changes in phase constitution, electrical resistivity and Vickers hardness with increase of Cr content were investigated in Ti-Cr binary alloys quenched from 1173 K. In solution treated and quenched state, hexagonal martensite, aЈ was identified at 3Cr and 5Cr alloys, whereas b phase was identified from 5Cr to 20Cr. In 7Cr and 10Cr alloys, athermal w was also identified. Resistivity increased with increase of Cr content up to 10 mass% Cr and then slightly decreased. Above 10 mass% Cr, resistivity at liquid nitrogen temperature was larger than that at room temperature. Maximum of HV appeared at 7 mass% Cr and then HV decreased with increase of Cr content up to 13 mass% Cr. Above 13 mass% Cr, HV slightly increased due to solution hardening by Cr addition. Temperature-resistivity curves of alloys from 10Cr to 20Cr were negative temperature dependence between 77 K and about 300 K. From change of the temperature-resistivity curves with Cr content, it is expected starting temperature of athermal w formation decreases with increase of Cr content. Trend of changes in HV of Ti-Cr, Ti-Fe and Ti-V alloys as a function of e/a was the almost same, though absolute these values of the three alloys are not same.

Effect of chromium content on mechanical properties of casting Ti-Cr alloys

“…In addition, the maximum in microhardness at 10 mass% chromium is believed to be a result of the strengthening/hardening effect of ω-phase. This is in agreement with previous results using Ti-7Cr 13,22) . The yield strength, tensile strength, and elongation of the Ti-Cr alloys with 15 or 20 mass% chromium in this study (888-873, 905-898 MPa, and 12% each) get the better of those of hardened Type 4 gold-base alloys (493-825, 690-830 MPa, and 1-12%) and Co-Cr alloys (500-710, 650-870 MPa, and 2-12%) [23][24][25][26] .…”

“…According to a previous report, addition of chromium to titanium causes a phase transition from α-phase to β-phase. As described above, Ikeda et al 22) suggested that the development of ω-phase increased hardness and Koike et al 13) noted that ω-phase decreased ductility. The increase in hardness was probably caused by the solidsolution hardening of the α-phase or the β-phase.…”

“…Shimizu reported an increase in tensile strength of binary Ti-Cr alloys with an increase in chromium content ranged from 10-20 mass%, however, the strength was reduced addition of chromium further more 9) . Ikeda et al reported that while the microstructure of binary Ti-Cr alloy fundamentally exhibited β-phase, when the chromium content ranged from 7-13 mass%, the alloy exhibited ω-phase, depending on cooling conditions, resulting in increased strength 22) . We believe that one possible explanation for the disparity between our results and those of these earlier studies may lie in the casting process used.…”

Comparative Study of Ti-<I>x</I>Cr-3Sn Alloys for Biomedical Applications

“…It has been reported that the reverse transformation from 00 (orthorhombic) phase to the phase causes shape recovery to appear. [17][18][19] Ti-Cr is also hopeful alloy system for biomedical applications and there are some reports on mechanical properties of Ti-Cr 20,21) and Ti-Cr-X alloys. [22][23][24][25] Selection of Ti-Cr-Sn alloy system was due to phase stabilizing effect of Cr, low melting points of Cr and Sn as compared to other phase stabilizing elements and solid solution strengthening effect of Cr and Sn (atomic radius: Cr ¼ 0:126 nm, Sn ¼ 0:158 nm, Ti ¼ 0:146 nm).…”

Development of α+β-type biomedical Ti–Nb alloys with high oxygen content

“…5 (a)), a significant increase in hardness was observed after heat treatment at 873-973 K and maximum hardness was obtained after heat treatment at 973 K. Under these conditions, athermal ω formed in these alloys after quenching, and its amount was larger in the alloy heat-treated at 973 K. Athermal ω is reported to increase the hardness of Ti alloy. [13,14] Therefore, this study suggests that an increase in hardness of these alloys was caused by the formation of athermal ω. No significant increase in hardness was observed in the alloys with oxygen content of 0.75 and 1 mass%.…”