Dissimilar joints of AA2219 and Ti-6Al-4V alloys are obtained using the vacuum Diffusion bonding method. The bonding pressure is controlled in the range of 1-4 MPa by keeping the bonding temperature and holding time constant. The influence of the bonding pressure on the microstructure and mechanical properties of the bonding joints is investigated. The Diffusion behaviour across the interface of the bonding joints is increased with the increase in bonding pressure. The interface morphology of the specimen bonded at lower bonding pressures exhibits scraggly voids and cracks. The irregular voids and cracks are squeezed and gradually closed due to the significant increase in the Diffusion between Al and Ti. The maximum shear strength of 81 MPa is obtained for the joint made at the bonding pressure of 4 MPa, and a Diffusion layer of 0.76 µm is formed at the Ti side interface. The fracture morphology inferred the brittle failure of the bonding joints due to the formation of intermetallic compounds like TiAl, TiAl2, and TiAl3 at the interface of Al and Ti.

Multilayered ceramic-metal composites were produced by solid state Diffusion bonding of polycrystalline alumina and three Al alloys containing 1 to 2%Sr, 2% Mg and Mg + Si (5057 Al alloy). The multilayered structures were fabricated at 610°C under a compressive stress of 3 MPa for 2 hours in He-5%H atmosphere. The ceramic-metal interfaces were studied by SEM and TEM equipped with an energy dispersive spectrometer (EDS). Addition of 1 wt % Sr to Al promoted good adhesion, without producing any interfacial products, while the Al-2wt%Sr was poor in this regard due to the presence of dispersed Al4Sr, which is an intrinsic phase in the Al-Sr phase system. The Al-2%Mg alloy produced a continuous film at the interface, which was characterized as being MgAl2O4. Al alloys containing Mg and Si (5057 commercial alloy) produced not only the spinel structure (MgAl2O4), but another phase rich in Mg and Si (close to Mg2Si). These latter interfacial reaction products were not the intrinsic phases in Al-Mg alloys, but were reaction products at the Al2O3 –Al alloy interfaces.

In this study, the effect of temperature on the microstructure and reactive layer at the interface between the Ti interlayer and the base metal related to the Diffusion bonding of Zr702 to A516 low alloy steel was investigated. The joining was done using the spark plasma sintering technique at temperatures of 900, 950 and 1000°C for 30 minutes. Field Emission Scanning Electron Microscope (FESEM) equipped with EDS analysis was used to investigate the microstructure of the interfaces in various joints. Investigations showed that at all temperatures, with the Diffusion of atoms and the formation of a reactive layer between the Ti interlayer and Zr702, no intermetallic phases, cracks, porosity and discontinuities were formed at their interfaces. . It was found that increasing the bonding temperature did not cause the formation of new phases and compounds in the interface and only increased the thickness of the reaction layer. The measurement of the thickness of the reactive layer showed that the maximum and minimum amounts of Diffusion were 84 microns at 1000 °C and 64 microns at 900 °C respectively.

In this research, the Diffusion bonding of the stabilized zirconia ceramic and Nimonic 105 superalloy using Ti/Nb/Ni multi-interlayer was carried out. Joint was performed using the plasma spark technique in a vacuum atmosphere and at different temperatures and times. The microstructure of the different joint zones was studied using optical and FESEM microscopes equipped with an EDS analyzer. The results showed that the critical region is Ti/3YSZ interface and in all conditions Diffusion bonding in Ti/Nb, Nb/Ni, and Ni/NI 105 interfaces were done. Microstructural observations showed that in the Ti/3YSZ interface at all temperature and time conditions, the connection of two separate regions including Ti3O and (Zr, Ti)2O was formed due to the difference in the Diffusion depth of Ti, Zr, and O elements and with increasing temperature and time, the thickness of these regions increased. Microstructural studies showed that the bond at 900 ℃ and 30 minutes did not have any cracks and discontinuities and due to the better Diffusion of atoms, a suitable reaction layer was formed. Microhardness observations and EDS analyses confirmed that the Ti3O reaction layer is the weakest zine.

AISI 304 stainless steel is joined by transient liquid phase Diffusion bonding, using an amorphous base nickel interlayer with a thickness of 50fLm. The bonding process was carried out at 1100°C under different atmospheres, air, argon and vacuum, at different bonding times of 30 to 180 min. The joints were then homogenized at 1150°C for 120 min. Microstructure studies showed that voids and cavities were formed at the joint region and the joint/parent alloy interface of bonds made under air and argon gas. The formation of these voids and cavities was related to the oxidation of the interlayer and joint/parent alloy interface during the bonding process. But, there were no voids or cavities at the bond region and joint/parent alloy interface when the bonding process was carried out in vacuum. Shear test results showed that the shear strength of bonds made under vacuum and then homogenized is very close to the shear strength of the parent alloy.

The Diffusion bonding of two dissimilar alloys Al 5083 and Mg AZ31 was carried out at 420, 430. 440 and 450 ° C for bonding time of 60 min. In order to characterize the microstructure evolution in the joint zone, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD) were applied. The results show that joint formation is attributed to the solid-state Diffusion of Mg and Al into Al 5083 and Mg AZ31 alloys followed by eutectic formation and constitutional liquation along the interface. At bonding temperature of 430° C Diffusion induced grain coarsening was observed at the interface. With increase in bonding temperature, the atomic diffusivity increases, results in easier and speeder chemical bonding. In bonding temperature of 440° C the weld had an irregular shaped region in the weld center, having a different microstructure from the two base materials. The irregular shaped region contained a large volume of intermetallic compound Al12Mg17 and showed significantly higher hardness in the weld center. The present study suggests that constitutional liquation resulted in the intermetallic compound Al12Mg17 in the weld center.

In this study the Diffusion bonding of steel– tungsten using a pure titanium interlayer was investigated. Samples were heated in a special fixture under 5 MPa pressure and at the different times and temperatures in the argon furnace. The images of optical and scanning electron microscopes indicated that a detectable diffused region was formed at the Ti- W, while no detectable diffused region was formed at the Steel- Ti interface. Also with increasing the time and or temperature of the process, the thickness of diffused region was increased. Results of the energy dispersive x- ray spectroscopy (EDX) approved the Diffusion of Ti and W and little Diffusion of steel and Ti. The results of x- ray diffraction (XRD) approved the presence of FeTi and Fe2Ti phases at the welded region. The results of microhardness indicated that the maximum hardness is related to the 1000T1H sample and spatially in its steel- Ti interface. This maximum hardness was due to the presence of intermetallic compounds (FeTi and Fe2Ti).Regarding to the results of shear test, 950T1H had the maximum shear strength and with increasing the time and temperature of welding, the strength was decreased due to the more intermetallic formation. Regarding all the results, temperature of 900 C and time of 1 hr, were found the optimum time and temperature for steel- tungsten Diffusion bonding.

Background: Prostate cancer is the third leading cause of death and is the most common cause of cancer in elderly men. Regarding to the low accuracy of screening methods such as prostate-specific antigen (PSA), Digital Rectal Examination (DRE) and trans rectal ultrasound (TRUS) in detection and localization of tumor, Magnetic Resonance Imaging (MRI) and Diffusion Weighted Imaging (DWI) attracted many attentions in the past years. DWI reveals micro-molecular Diffusion, which is the Brownian motion of the spins in biologic tissues. This technique can delineate pathologic lesions with high tissue contrast against generally suppressed background signal. In this paper, the value of DWI in detection of prostate cancer is studied.Methods: In this cross-sectional study, the studied population are suspicious patients to prostate cancer based on high Prostatic Specific Antigen level or abnormal Digital Rectal Examination who refered for prostate biopsy to radiology department of Hazrate- Rasoul Hospital during the year 2011. The results of DWI are compared to biopsy results for all patients.Results: Eighty five patients are selected. The DWI sensitivity in detecting of prostate cancer is 100%, specificity 97.1% and positive and negative predictive values are 89.5% and 100%, respectively. The results showed that if DWI reports the prostate cancer as negative, the result was highly reliable and if it reports as positive, although the report was not 100% reliable, but it still had high reliability, more than 90%.Conclusion: DWI had high accuracy in detecting prostate cancer for patients with cancer. Also the accuracy of this method for patients without prostate cancer was acceptable compared to the other common methods.

Background: Multiple sclerosis (MS) is a chronic disease that begins most commonly in young adults and is characterized pathologically by multiple areas of central nervous system (CNS) white matter inflammation, demyelination, and glial scarring. The most valuable aid for diagnosis is magnetic resonance imaging (MRI). New type of MRI has been developed on the basis of molecular Diffusion which capable of detecting acute and active lesions. Early diagnosis and treatment is possible to stop or slowdown progression of disease. The aim of this study is to compare the findings of conventional and Diffusion- weighted (DW) MRI in detection cerebral lesions of MS.Methods: Thirty patients with clinically definite MS and 30 healthy volunteers were studied in a descriptive-prospective survey over a twelve-month period of time.Conventional and DW MRI were used in both groups. Total number, morphology, location and the mean size of the intra-cerebral plaques of MS were compared between group. The sensitivity and the specificity of both imaging methods in detecting these plaques were determined.Results: Thirty patients with MS with the mean age of 32.76±8.79 years and 30 healthy individuals with the mean age of 32.75±9.23 years were enrolled. Plaque within the brain was significantly higher by the conventional method (P<0.05). Ovoid lesions were greater in number in the conventional method group. More lesions were detected by the conventional method in the areas of periventricle, centrum semiovale and corpus callosum. Regarding the size of plaque, the minimum measurement was significantly lower in the conventional method group. The sensitivity of both methods was 100%. The specificity of conventional and DW MRI was 86.6% and 96.6%, respectively.Conclusion: In our study the sensitivity of both methods was the same but the specificity of DW MRI was higher. DW MRI may detect lesions which are not detectable by the routine methods.