A combinatorial approach using diffusion couples and advanced characterization was carried out to investigate the composition-dependent interdiffusion and mechanical properties of γ-Ni(Al) solid ...solution, γ′-Ni3Al and β-NiAl. The diffusion couples between pure Ni and Ni52Al48 were annealed at temperatures of 1000 °C, 1100 °C and 1200 °C for 96 h, 48 h and 24 h, respectively. The γ-Ni(Al), γ′-Ni3Al and β-NiAl have developed in the diffusion zone. The β-NiAl transformed to martensite above room temperature when Al is less than 37 at.%. The composition-dependent interdiffusion coefficients for all phases corresponded closely to previous research. A systematic composition-dependent elastic modulus and hardness for γ-Ni(Al), γ′-Ni3Al and β-NiAl phases were obtained by nanoindentation. Variation of elastic modulus and hardness in the γ-Ni(Al) solid solution is influenced by solid solution strengthening and hardening due to precipitation of γ′-Ni3Al while cooling. The evolution of elastic modulus and hardness in the β-NiAl phase exhibited a minimum value of elastic modulus and hardness near the phase boundary between martensite and austenite. Lattice softening associated with martensitic transformation was recognized to lower the value of elastic modulus and hardness.
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•Composition-dependent interdiffusion coefficients of γ-Ni(Al), γ′-Ni3Al and β-NiAl phases.•Composition-dependent modulus and hardness of γ-Ni(Al), γ′-Ni3Al and β-NiAl phases using nanoindentation.•Martensitic transformation in β-NiAl contributes to the change in modulus and hardness.
Well-adhered nanotube arrays were produced through the anodizing technique on a Ti-25Nb-25Ta alloy and tribo-mechanically evaluated by nanoindentation and nanoscratch tests. Disregarding substrate ...effects, the hardness of the nanotube arrays layer was 0.7 ± 0.1 GPa and elastic modulus was < 12 GPa, respectively. With the load increase and nanotubes compaction, hardness reached 1.8 GPa and elastic modulus stabilized in ∼40 GPa, which features a mechanically biocompatible gradient zone for implant applications. Under scratching, plastic deformations predominated in the nanotube arrays coating, which mechanism was load-dependent: in the first stage (up to 50 mN) and the initial tubes collapsing, the coating presented low cohesive strength; under higher loads and the progressive nanotubes compaction, the cohesive strength increased, as suggested by the pattern of cracks produced. The scratch resistance for the coating failure was higher than 500 mN, consisting of an excellent bonding adhesion for a nanotube layer produced by anodization.
This article focuses on testing of glued laminated timber beams and researching their properties. The article mainly focuses on comparison of measured modulus of elasticity obtained by two different ...methods. First method used was method of spike which has non-destructive character. This method was used to measure properties of glued laminated timber (GLT) on macro mechanical level in form of modulus of elasticity. Second method was used to determine micromechanical properties of material and is called nanoindentation. Tested material will be also described the article along with principle of testing and presenting results. Those results of individual measurements will be compared with respect to percentage representation of individual phases on micromechanical levels to measurement on macromechanical level.
Solder joints provide mechanical support, electrical and thermal interconnection between packaging levels in microelectronics assembly systems. Proper functioning of these interconnections and the ...reliability of the electronic packages depend largely on the mechanical properties of the solder joints. Lead free solders are common as interconnects in electronic packaging due to their relatively high melting point, attractive mechanical properties, thermal cycling reliability, and environment friendly chemical properties. However, environmental conditions, such as, operating temperature, aging temperature, and aging time significantly affect these properties due to the microstructural evolution of the solder that occurs during aging. Moreover, electronic devices, sometimes experience harsh environment applications including well drilling, geothermal energy, automotive power electronics, and aerospace engines, where solders are exposed to very high temperatures from T = 125-200 °C. Mechanical properties as well as microstructural study of lead free solders at elevated temperatures are limited in literature. Previous investigations on the microstructural evolution mainly emphasized on aging at temperatures up to 125 °C. In addition, those studies were limited on investigating the coarsening of Ag 3 Sn IMC particles within the beta-Sn matrix.In this work, the microstructural evolution of SAC305 (96.5Sn-3.0Ag-0.5Cu) BGA joints were investigated for different aging conditions utilizing Scanning Electron Microscopy (SEM). In particular, our approach has been to monitor aging induced microstructural changes occurring within fixed regions in selected lead free solder joints, and to create time-lapse imagery of the microstructure evolution. Aging was performed at T = 150 °C for several durations up to 20 days, and the topography of the microstructure of a fixed region was captured using the SEM system. This process generated several images of the microstructure as the aging progressed. We have also explored the Mechanical behavior, and aging effects of SAC305 solder joints at extreme high testing temperatures of T = 150 °C using the method of nanoindentation. To study the aging effects, solder joints were preconditioned for 0, 1, 5, 10, and 30 days at T = 125 °C in a box oven. Nanoindentation testing was then performed on the aged specimens at a test temperature of T = 150 °C to extract the elastic modulus, hardness, and creep performance of the aged material.As expected, the analysis of the evolving SAC305 BGA microstructure showed a significant amount of diffusion of silver and copper in the beta-tin matrix during aging. In addition, the growth of the copper-tin layer at the solder joint and copper pad interface at the PCB side has been visualized, and then measured as a function of aging time and temperature. Quantitative analysis of the evolving microstructure showed that the particles coalesced during aging leading to a decrease in the total number of particles. This caused an increase in the average diameter of the particles with aging time, and a double exponential empirical model was used to fit the observed data. The nanoindentation test results also showed a huge degradation in the mechanical properties with the aging time. The time dependent evolution of the microstructure was compared to the degradation in the modulus during aging, and good correlation was observed.
