Takashi Sugimoto

Effect of two phase warm rolling on aging behavior and mechanical properties of Ti–15Mo–5Zr–3Al alloy

Abstract The isothermal aging behavior and change in tensile and mechanical properties of Ti–15Mo–5Zr–3Al alloy have been studied after three different pre-treatments, i.e. PR (rolling at partial solution temperature), PRP (PR+partial solution treatment) and C (complete solution treatment) by hardness and resistivity measurements, tensile and Charpy impact tests. After the PR and the PRP treatment, almost all of the plate-like primary α particles which were left in as-received specimens became granular, furthermore age-hardening was observed in that α+β bi-phased specimens. Plate-like α is always formed by the aging. Sub-grain size of β phase in the PR and the PRP specimens is 1–2 μm, and no grain growth is observed during the aging. Tensile properties after 673 K-600 ks or 773 K-60 ks aging are improved by the PR or the PRP than the C pre-treatment. The fracture surface of the aged and tensile tested PR and PRP specimens shows dimples, whereas that of the C specimen shows flat surface, area fraction of 40–50%, due to grain boundary fracture. Deflection–load curve shows practically no change in its shape with variation in the pre-treatment, however maximum load is highest in the PRP specimen and decreases in order of the PR and the C. Total absorbed energy is also larger in the PR and the PRP specimens than in the C specimen in age-hardened state. The best strength–ductility balance is attained by the PRP specimen aged at 773 K for 60 ks.

Compositional structure of dual TiNO layers deposited on SUS 304 by an IBAD technique

Abstract Surfaces of stainless steel SUS 304 were coated with dual titanium oxynitride (TiNO) layers using a nitrogen ion beam-assisted deposition technique. The N ions were accelerated at energy of 0.5–2.0 keV with an intensity of 0.1 mA/cm 2 on the substrate surface. First, a TiNO film was deposited on substrates at 700 °C, and subsequently, another TiN film was deposited on the previous TiNO film surface at 400 °C. Hydrogen carbon nitride, CrFe, and metal carbide M 23 C 6 were produced in the near-surface region of stainless steel during the TiNO deposition at 700 °C, and three characteristic layers consisting of iron nitride, chromium nitride and nickel nitride were formed between the TiNO films deposited and the stainless steel. These characteristic layers disappeared during deposition of the TiNO layer at a temperature of 400 °C.

Aging behaviour of Ti15Mo5Zr and Ti15Mo5Zr3Al alloy up to 573 K

Abstract Aging behavior of Ti 15Mo 5Zr (15-5) and Ti 15Mo 5Zr 3Al (15-5-3) alloys isothermally aged below 573 K has been investigated mainly through resistometry. In the 15-5 alloy, resistivity at 77 K (ϱLN) increases only slightly, whereas the resistivity at room temperature (ϱRT) increases greatly. The ϱ of the 15-5-3 alloy shows the same tendency as that of the 15-5, but the increase in ϱ continues for a longer period and the increment is larger than in the 15-5 alloy. X-ray diffraction and hardness of the 15-5-3 suggest a long incubation period for the precipitation of the aged ω phase, in contrast to that of a 15-5 alloy aged between 623 K and 723 K. The increase in ϱRT of these alloys might be best interpreted as the concentration separation of β matrix, like GP zones in Al alloys, which contributes to a significant increase in ϱ but to only a minor increase in hardness. Also with α precipitation at high aging temperature, a slight increase is observed in ϱLN during an apparent incubation period. These results suggest that the concentration separation of β occurs at both high and low aging temperatures and that suppression of aged ω by Al addition makes the ϱ increase conspicuous.

Relationship between hardness and lattice parameter for TiN films deposited on SUS 304 by an IBAD technique

Abstract Titanium nitride films were deposited on SUS 304 stainless steel using an ion beam-assisted deposition technique. The N ions were accelerated at energy of 0.5–2.0 keV with an intensity of 0.1 mA/cm 2 on the substrate. Substrates were held at temperatures of 400–770 °C during deposition. For the TiN films, hardness was in the range from 350 to 550 GPa, depending on the N ion-beam energy, while the lattice parameter was dependent on the N ion-beam energy and substrate temperature. The lattice parameter dependence of hardness for the TiN films deposited at temperatures lower than 600 °C differed from that for films deposited at temperatures above 700 °C.

Dependence of film thickness on nitrogen ion energy and substrate temperature for titanium nitride films on stainless steel using an ion beam assisted deposition technique

Abstract Stainless steel (SUS-304) was coated with titanium nitride (TiN) using a ion beam assisted deposition (IBAD) technique. The deposited TiN films were polycrystals oriented in the 〈1 1 1〉 〈2 0 0〉 and 〈2 2 0〉 directions. The thickness of the deposited TiN films was measured using Rutherford backscattering spectrometry with He ions. The thickness of the films decreased with increasing N ion energy, and they were not dependent on substrate temperature but significantly decreased with substrate temperature above a specific temperature for SUS-304 because the sticking coefficient of Ti to SUS-304 was less than unity.

Titanium oxy-nitride films deposited on stainless steel by an ion beam assisted deposition technique

Surfaces of stainless steel SUS304 were coated with titanium oxy-nitride (TiON) films at temperatures of 400–770°C using an ion-beam assisted deposition technique constructed from an electron beam evaporator for Ti evaporation and a microwave ion source for ionizing nitrogen gas. The N ions were accelerated at energies of 0.5–2.0 keV. Most of the deposited TiON films consisted of (60–80)% TiN and (40–20)% TiO2, and the fraction of TiO2 increased with increasing substrate temperature. Hardness of the TiNO films varied in the range from 160 GPa to 260 GPa with increasing substrate temperature. The titanium oxy-nitride film could be deposited on stainless steel without a significant deterioration surface layer at 600°C. However, when TiNO films were deposited at temperatures higher than 700°C, the thickness of the TiNO films were significantly thinner and a thick layer containing nitride such as Cr2N, CrFe, Fe2N and Fe4N was formed in a near surface region of stainless steel because more nitrogen diffused into stainless steel.

Development of DLC Coated Tool for Cutting of Aluminum Alloy －Influence of Deposition Condition on Cutting Characteristic－

Conventional coating tools have a high affinity for ductile materials, like aluminum alloy, so cutting chips tend to adhere to cutting edge and work material surface. Therefore, chipping is caused, and surface texture is degraded. In order to solve these problems, recently, DLC (Diamond-Like-Carbon) has been applied to coating material. In this research, it is curried out cutting of Aluminum alloy by the use of DLC coating tool, and examined influence of DLC coating conditions on cutting characteristics. So far we have been concerned with the effect of type of hydrocarbon gas (acethylene:C2H2, methane:CH4) on cutting. As a result, it is revealed that cohesion of chips decreases, and surface roughness of work material improves in the case of acethylene-DLC. On the other hand, internal stress is produced by deference in hardness between tool surface and DLC film, and which is considered cause of film peeling [1]. Therefore, we examined interlayer between DLC film and tool surface in order to relax of internal stress. As a result, it was cleared that Titanium interlayer excels in adhesion.

Modification of the surfaces of stainless steel during titanium nitride deposition by a dynamic mixing method

Abstract Surfaces of stainless steel SUS304 were coated with titanium nitride (TiN) at temperatures ranging from 400°C to 770°C using a dynamic mixing technique. The N+ ions were accelerated at energies of 0.5–2.0 keV, and were implanted into the stainless steel. The composition of the prepared TiN films was measured using Rutherford backscattering spectrometry with He ions at an energy of 2.0 MeV. Intermediate layers containing compounds such as FesNq, Cr2N, and CrFe were formed between the TiN films and substrates at substrate temperatures higher than 700°C. The thickness of the TiN films decreased significantly when the intermediate layers were formed.

Change of Thermal Conductivity of Ti-20V and Ti-15V-3Cr-3Sn-3Al Alloys Below Room Temperature with Isochronal Aging

Thermal conductivity, K near liquid nitrogen temperature and electrical resistivity, p at liquid nitrogen temperature were measured on Ti-20V and Ti-15V-3Cr-3Sn-3Al (Ti-15-3) alloys. K of both alloys after solution treatment and water quenching was lower than that of 18Cr-8Ni stainless steel. With isochronal aging, isothermal ω and α precipitated in Ti20V alloy and only a precipitated in Ti-15-3 alloy. Both species of precipitates increased the K and decreased the ρ. Relation between K and T K/ρLN, which were changed by isochronal aging, was almost linear in both alloys though gave different gradients for each precipitates and alloys. Maximum K values of present β Ti alloys range from 4 to 6 Wm−1K−1 near liquid nitrogen temperature, which are about a half or two thirds of 18Cr-8Ni stainless steel.

Nitrogen ion dose dependence of surface morphology of titanium nitride films deposited on gallium arsenide by an ion beam assisted deposition technique

A thin titanium film was deposited on GaAs surfaces by an ion beam assisted deposition technique, and subsequently a titanium nitride film was deposited on the Ti/GaAs structure. The nitrogen ions were accelerated to an energy of 500 eV. The TiN films were deposited under a constant N ion current of 0.1 mA/cm/sup 2/, and the fraction of nitrogen ions in nitrogen beams was varied by varying nitrogen flow rate. The Ti layers changed to a Ti-rich TiN layer during the TiN deposition because nitrogen ions were implanted and diffused into the Ti layer. The surface morphologies of the structures varied with the dose of nitrogen ions and on annealing temperature. The film deposited at a flow rate of 10 sccm had a surface smoother than that at 20 sccm even after it was annealed at 1000/spl deg/C. Neither blister nor crack run on the surface of the former annealed structures. That is, the nitrogen ions contributed to keep the smooth TiN film surface during high temperature annealing and to prevent blistering and cracking of the films.