Compressive Residual Stress into Titanium Alloy Using Cavitation Shotless Peening Method

Cavitation shotless peening (CSP) method, where impacts are generated by a submerged cavitating jet (without shots), was used to introduce compressive residual stress in titanium alloy, Ti-6Al-4V for the purpose of enhancing the conventional fatigue and fretting fatigue life and strength. This method provided higher compressive stress at surface as well as up to a depth of 40 m from the surface than that with the shot peening method. Further, the surface treated by CSP was considerably less rough compared to that by the shot peening method, which is a highly desirable feature to improve the fretting fatigue performance.     

Effect of nozzle geometry on a standard cavitation erosion test using a cavitating jet

In order to accurately and reliably evaluate the cavitation erosion resistance of materials using cavitating jet apparatus according to ASTM G134, the effect of various types of nozzle geometries on the erosion rate was investigated. As the erosion rate depends on the erosion time and the distance from the nozzle to the specimen, i.e., the standoff distance, the mass loss as a function of erosion time at the optimum standoff distance was measured. It was shown that the erosion rate depended on the nozzle geometry. In fact, the aggressive intensity of the cavitating jet I_J depends on the nozzle geometry. When a cavitating jet of low I_J was used in the erosion test, it took some time to reach the maximum cumulative erosion rate E_Rmax, which is recommended in ASTM G134 as a parameter for determining the cavitation erosion resistance of materials. In the present experiment, the difference in E_Rmax was more than 600%, and the time required to reach E_Rmax was also scattered over 600%, for the different nozzles used. It was also revealed that E_Rmax could be obtained from the product of I_J and the reciprocal of the relative cavitation erosion resistance of the material, R_ER.     

Microstructure and mechanical properties of a rapid solidified boron- modified duplex stainless steel

Two duplex stainless steels 2205 and 2205 with 2.5?wt-% B addition prepared by a fast solidification technique were investigated. The samples were arc melted and cast in a cylindrical mould with varying diameters in a single cavity that provided different cooling rates. The hardness increased in both cases for smaller diameters, however, there was a different profile from the surface to the centre in case of 2205 with 2.5?wt-% B. The microstructural investigation indicated that boron addition led to the formation of hard borides and grain refinement. Different boride morphologies that varied with the cooling rates were identified. The compression strength at room temperature improved by a factor of 3.5 with boron addition without considerably decreasing the ductility.     

A microwave probe nanostructure for atomic force microscopy

An atomic force microscope (AFM) probe on a GaAs wafer was studied as a new microwave probe structure. A waveguide was created by evaporating an Au film on the top and bottom surfaces of the GaAs AFM probe. The fabricated AMF probe’s tip is 8 μm long and has a radius of curvature of about 50 nm. The open structure of the waveguide at the tip of the probe was generated by using focused ion beam (FIB) fabrication. AFM topography of a grating sample was created by using the fabricated microwave AFM probe. The fabricated probe exhibits nanometer-scale resolution, and microwave emission was successfully detected at the tip of the probe by approaching Cr–V steel and Au wire samples.     

Preparation and evaluation of sub-100 nm Pb(Zr,Ti)O3 films derived from modified sol-gel solutions for low-voltage operation of feram

Abstract

Sub-100 nm PbZr_0.3Ti_0.7O₃ (PZT) films were prepared on Pt/SiO₂/Si substrates from modified sol-gel solutions without using any seeding layers. Firstly, we studied Pb content [Pb/(Zr+Ti)] dependence of 90-nm-thick films. In the wide Pb content region of 108 – 125%, the films had perovskite-single-phase fine columnar grains with (111)-orientation and no voids. Electric properties were dependent on Pb content. The film with good microstructure, rectangular hysteresis, high remanent polarization (P_r), and low leakage current was gained for Pb content of 116%. Secondly, we studied film thickness dependence of PZT(116/30/70) films. Films from 90 down to 61 nm in thickness were prepared. We found that the sub-100 nm films with good microstructures could be prepared from the modified solutions. The sub-100 nm films had saturation voltage of 1.25 V and high P_r even at 1 V or less. In particular, a 61-nm-thick film had high.P_r of 17 μC/cm2 at 0.75 V.     

The effect of scanning pitch of nozzle for a cavitating jet during overlapping peening treatment

The objective of this paper is to optimize the pitch at which the nozzle of a cavitating jet is scanned during peening. The evaluations of an effect of the pitch on overlapping treatment are done, firstly theoretically, by estimating the aggressive intensity of the jet based on a Gaussian distribution in order to uniformly and effectively treat the surface in applications such as cavitation peening and cleaning. Experimentally, cavitation peening was conducted with the nozzle scanned at various pitches. Striped patterns, due to the non-uniform treatment, were formed in aluminum when pitches of 6, 8, 10 or 12 mm were used, whereas with pitches of 2 and 4 mm the patterns were uniform. The compressive residual stress introduced into type 316L stainless steel by cavitation peening was approximately 380 and 400 MPa for pitches of 2 and 4 mm, respectively. From the viewpoint of not only the uniformity but also effective and efficient treatment, the optimum pitch for scanning was determined to be 4 mm, since this requires half the number of scans compared to 2 mm.     

RA70 is a src kinase-associated protein expressed ubiquitously

RA70, which is expressed during neuronal differentiation of P19 EC, is highly homologous to human src kinase-associated phosphoprotein (SKAP55). Here we isolated human full-length RA70 cDNA. Unlike SKAP55, which is specifically expressed in thymus and T cells, RA70 was expressed ubiquitously in various tissues including lung, skeletal muscle, and spleen, and in various cell lines including human monocytic leukemia (U937) cells, but RA70 was undetectable in thymus and T cell lymphoma (Jurkat) cells. RA70 as well as SKAP55 proved to be a protein with molecular weight 55 kDa associated with SH2 domain of Fyn. Interaction between RA70 and src family kinases, Fyn, Hck and Lyn, was detected during monocytes/macrophage-differentiation of U937 cells. Thus, like SKAP55, RA70 is an adaptor protein of the src family kinases. RA70 may play an essential role in the src signaling pathway in various cells.     

Sintering Behavior and Microstructure Formation of Titanium Aluminide Alloys Processed by Metal Injection Molding

The sintering behavior of metal injection molded titanium aluminide alloys, their microstructure formation and resulting mechanical properties were investigated. As reference material, the alloy Ti-45Al-5Nb-0.2B-0.2C at.% (TNB-V5) was selected. Additionally, two other variations with Mo and Mo + Si additions were prepared: Ti-45Al-3Nb-1Mo-0.2B-0.2C at.% and Ti-45Al-3Nb-1Mo-1Si-0.2B-0.2C at.%. The results indicate that the optimum sintering temperature was slightly above the solidus line. With proper sintering parameters, very low porosities (<0.5%) and fine microstructures with a colony size <85 µm could be achieved. Considering the sintering temperatures applied, the phase transformations upon cooling could be described as L + β → β → α + β → α → α + γ → α₂ + γ, which was in agreement with the microstructures observed. The effects of Mo and Si were opposite regarding the sintering behavior. Mo addition led to an increase in the optimum sintering temperature, whereas Si caused a significant decrease.