Defect and Diffusion Forum Vol. 329

Abstract: The Volume Diffusion of Homovalent Atomic Probes (APs) from the VIB Group of the Periodic Table of Elements (PTE): Сr, Mo, W and from the VIIB Group of the PTE: Mn, Tc, Re in W Single Crystals Has Been Studied by Using Secondary Ion Mass Spectrometry (SIMS) and Radiometric Layer-by-Layer Analysis. the Enthalpies Q of the Bulk Diffusion of Homovalent APS from the VIB Group (Сr, Mo, W) and from the VIIB Group (Mn, Tc, Re) of PTA Increase with the Growth of N Numbers of their Periods in each Group whereas the Relaxation Volumes  of the Complexes “va-Cancies- VIB, VIIB Aps” in the W Lattice Do Not Differ Practically. the Detected Change of En-Thalpies Q Is Conditioned by the Difference in Magnetic Moments of Homovalent Aps from the VIB and VIIB Groups of PTA in Complexes with Vacancies in the W Lattice.

Abstract: To Study the Defect Properties in the Crystal, it Is Necessary that they Are Present in Sufficiently High Concentration. Electrical Measurements Are Also One of the Oldest Techniques Used in Materials Science. this Paper Aims to Discuss the Possibility of Using Electrical Measurements as Diagnostic Techniques for Detecting Defects in a Set of Plastically Deformed Pure and 3003 Al Wrought Aluminum Alloys. the Results of Electrical Measurements Were Analyzed in Terms of the Variation of Resistivity. this Model Can Be Used to Investigate both the Defect and Dislocation Densities of the Samples under Investigation. Results Obtained by Means of Electrical Techniques Have Been Reported. Plastic Deformation Was Performed, and I-V Curves Were Measured in Order to Determine the Value of the Resistivity. the Values of Resistivity as a Function of Deformation and Annealing Behavior Were Studied. One of the Goals of the Work Was to Obtain the Activation Energy for the Formation of Defects by Performing Electrical Measurements on both Materials (pure Al and 3003 Al Alloys ).

Abstract: Nanostructured Powders of Ni-20wt%Al and Ni-50wt%Al Were Prepared, by Mechanical Alloying under an Argon Atmosphere, from Elemental Ni and Al Powders Using a Planetary Ball Mill (type Fritsch P7) for Different Times (0.5-24h).). Microstructural and Structural Features of the Final Products Were Characterized by X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). the Results of the XRD Shows the Formation of the B2 (Ni Al) Phase after 2 Hours of Milling for both Systems. Also Detected Was the Ni₃al Phase in Ni₈₀al₂₀ after 4 Hours. Crystallite Size Refinement of the Final Product Occurred down to Nanometer Scales when the Milling Time Increased, and Attained 17 Nm in the Ni₅₀al₅₀ System and 20 Nm in the other System, at 24 Hours. this Decrease in Crystallite Size Is Accompanied by an Increase in the Interval Level Strain. the Kinetics of Al Dissolution during the Milling Process of Ni₅₀al5₀ System Can Be Described by Two Regimes, Characterised by Different Values of Avrami Parameters which Are Calculated by Using the Johnson–Mehl–Avrami Formalism.

Abstract: The Positron Annihilation Lifetime Technique (PALT) Is One of the Most Important Nuclear Non-Destructive Techniques. it Was Used to Study the Activation Enthalpy for Defect Formation in 5754 Alloy. Quenching Experiments Were Usually Performed on Thin Specimens to Ensure a Uniform Quenching Rate throughout the Specimen. from such Measurements, it Is Possible to Deduce the Vacancy Formation Enthalpy which, in Combination with the Results of Self-Diffusion Measurements, Gives a Value for the Migration Enthalpy of the Vacancy. these Are Very Important Quantities in the Study of the Annealing of Irradiation-Induced Defects. the Use of the Quenching Technique in the Positron Annihilation Study Has the Advantage that it Allows a Distinction to Be Made between Vacancies and Dislocations. Correlations between Nuclear, Electrical and Mechanical Methods Have Been Carried Out after Quenching.

Abstract: Austenitic Stainless Steel Has a FCC Structure at Room Temperature and the Temperature Range of the Austenite Phase Depends upon its Composition. 316L SS Is Widely Used in Medical, Marine, Industrial, Sporting and Aerospace Applications due to its Excellent Combination of Mechanical Properties and Corrosion Resistance. this Study Presents the Defects Observed during Optimization of the Processing Parameters for the Fabrication of Powder Injection Molding (PIM) of 316L SS Parts. in this Study, Five Formulations of Feedstock Containing 60-71vol% of Metal Powder Were Prepared Using a Wax-Based Binder. Green Samples Were Injection-Moulded, Followed by Binder Removal by Solvent and Thermal Means. Paraffin Wax (major Binder) Was Extracted at Various Temperatures in Order to Determine the Solvent Extraction Temperature. the Thermal De-Binding Was Performed Successfully at a Temperature of 450°C by Varying the Heating Rate from 1°C/min -10°C/min. SEM Results Showed Complete Removal of the Plastic Binder. Test Samples Were Sintered at Various Temperatures and Atmospheres. the Defects Observed during Solvent Extraction Were Swelling, Cracks and, at the Thermal De-Binding Step, Collection of Binder, Swelling and Holes. Sintered Samples Showed a Loss of Dimensional Control. these Types of Defect Were Considered to Be due to Inappropriate Heating Rates, Temperature and Dwell Time at each Process Step.

Abstract: Tin Brass Heat Exchanger Tube Was Hydrogen-Charged under Various Cathodic Charging Conditions. the Introduction of Charged Hydrogen into Tin Brass Tube Was Found to Induce Hardening of its Surface. the Severity and the Depth of the Hardened Region Was Observed to Increase with either Cathodic Current Density or Charging Time. Ageing after Charging Results in either Complete or Partial Recovery of Hardness, Depending upon the Charging Conditions Applied to the Heat Exchanger Tube.

Abstract: The Objective of this Research Was to Investigate the Use of a Sensor System to Monitor Continuously the Defect Formation Response of Heat-Treatable Aluminum Alloys. the System Continuously Monitors a Material Property, Resistivity, which Is Indicative of the Quenching Process. such Studies Will Allow us to Gain Active Control of the Aging Process and Hence the Material Properties of Aluminum Alloys.

Abstract: Heat Treatments for Different Aging Times Were Performed on 2024 Aluminum Alloy. the Effect on the Positron Lifetime, Electrical and Mechanical Properties of the 2024 (Al-Cu-Mg) Alloy Was Studied. Artificial Ageing Was Conducted by Heating at a Constant Rate to a Specific Temperature, Followed by Annealing. the Alloy Was Treated at 192°C for Various Times, Followed by Annealing. Measurements as a Function of Aging Time Were Found to Exhibit Prominent Changes Related to the Formation of Precipitates.

Abstract: In this Paper, the Heat Transfer Performance in an Enclosure Including Nanofluids Is Studied. the Velocity Field Is Solved by an Incompressible Generalized Lattice Boltzmann Method and Heat Transfer Is Simulated Using Single-Relaxation-Time Lattice Boltzmann Method. the Hydrodynamics and Thermal Fields Are then Coupled Together Using the Boussinesq Approximation. the Fluid in the Square Cavity Is a Cu-Water Nanofluid. the Effects of Grashof Number and Solid Volume Fraction on Thermal and Hydrodynamic Characteristics Are Investigated. the Results Obtained Clearly Show that Heat Transfer Enhancement Is Possible Using Nanofluids in Comparison to Conventional Fluids. Comparisons with Previously Published Works Are Performed and Found to Be in Excellent Agreement with Existing Data.

Abstract: A Brief Sketch of Different Models for the Calculation of Defect Parameters in Metals and Alloys, Comparison of Data and Limitations Has Been Reviewed here; Especially Relaxations due to a Vacancy Type of Point Defect, its Formation, Migration, Activation Energies and Related other Parameters Based upon the Present Experimental Status. the Models Reviewed Are the Bond Model, Continuum Model, Semi-Discrete Model, Jellium Model, Thermodynamic Model, Lattice Statics Model, Atomistic Continuum Model and Pseudopotential Model. the Main Thrust Concerns the Last Model. the Taylor, Vashishta and Singwi, Harrison, Kleinmann and King and Kutler Form of Exchange and Correlation Function Are Almost Similar, Give Moderate Results and May Be Trusted for Better Results.