Papers by Keyword: EBSD

Abstract: The influence of strontium addition on the microstructure of a Mg-9Al-2Ca alloy was investigated. The microstructure of Mg-9Al-2Ca-xSr alloys consists of α-Mg, (Mg,Al)₂Ca with C15 structure, Al₄Sr and Al_xMn_y phases. The addition of strontium decreases the grain size of the α-Mg phase and decreases the aluminum content dissolved in the α-Mg solid solution. Moreover, the volume fraction of the Al₄Sr phase increases with increasing strontium content. Strontium does not influence on the volume fraction of (Mg,Al)₂Ca phase.

Abstract: Turbine discs in the gas turbine engine experience a wide range of stress and temperature during service. These result in distinct deformation mechanisms characteristic of different temperatures and stresses, and the cumulative effect of these on fatigue life is of much interest as turbines run hotter and thermal stresses rise. Thermo-mechanical fatigue tests are used to investigate performance at specific disc locations and have been performed on the alloy RR1000, a nickel based superalloy. This work describes a series of examinations to explore the interaction between temperature-loading conditions, deformation and failure mechanisms of an out-of-phase, largely compressive, thermo-mechanical cycle. Fatigue cracks initiated in the corners of the rectangular-sectioned test pieces and propagated to form approximately quarter-circle cracks. The interaction of the microstructure and deformation mechanism with the crack growth path has been investigated using Electron Backscatter Diffraction (EBSD) analysis complemented by Transmission Electron Microscopy (TEM) of specimens sampled from specific locations in the vicinity of a secondary crack.

Abstract: In the present investigation friction stir processing (FSP) is carried out using multipass FSP on a 5086 aluminum alloy to modify microstructure and mechanical properties. Two processing conditions P1 and P2 were used, P1 is carried out at constant rotation speed of 1025 rpm and at a traverse speed of 50 mm/min, P2 is carried out at constant rotation speed of 720 rpm and at a traverse speed of 155 mm/min. Inhomogeneous microstructural distribution was observed across the processed zone. EBSD analysis has been done to evaluate the microstructure. Overlapping passes is showing same grain size in the FSPed material. Material processed using P2 processing condition is showing maximum superplastic ductility. The bulk material produced due to multipass FSP seems to be good for superplastic forming applications.

Abstract: Cube texture formation of Cu-33 at.%Ni alloy substartes and CeO₂ buffer layer prepared by chemical solution deposition on the textured substrate were investigated by electron back scattered diffraction (EBSD) and XRD technics systematically. The results shown that a strong cube textured Cu-33at.%Ni alloy substrate with the cube texture fraction of 99.8 % (< 10°) was obtained after annealing at 1000°C for 1 h. The full width half maximum (FWHM) values for the X-ray (111) phi-scan and (002) omega-scan in this substrate were 7.31° and 5.51°, respectively. Furthermore, the cube texture fraction of epitaxially grown CeO₂ buffer layer was 95 % (< 10°), and the FWHM values of phi-scan and omega-scan being 6.98° and 5.92°, respectively.

Abstract: The present work focuses on the experimental multi-scale characterization of fracture of an AISI 4135 steel by using the Disk Pressure Test (DPT). In order to precise the specific features of hydrogen embrittlement, comparison was made between disks burst under helium and hydrogen gas. SEM - EBSD analysis of disks samples before and after the test allowed to analyze and to compare the main microstructural mechanisms of the failure process. The location of the main crack initiation was consistent with Finite Element (FE) simulations of the DPT.

Abstract: Specimens of the common cast alloy Al-7Si-0.3Mg (A356) were solution heat treated at different temperatures and times to modify (i) the precipitation strengthening effect in the aluminum solid solution phase and (ii) to spheroidize the eutectic silicon. Just 15 minutes of solution heat treatment at a temperature of 540°C are sufficient to reach the desired effect. Cyclic loading experiments revealed an increase in fatigue life as compared to specimens heat treated at lower temperatures. In particular in the HCF regime, fatigue cracks that were originally initiated at pores follow crystallographic slip bands under shear control (mode II) as it was proven by automated EBSD (electron back scatter diffraction) measurements. The smoothly polished surface of the fatigue specimens was observed continuously by a long-distance microscope and discontinuously by SEM (scanning electron microscopy) to identify the fatigue crack propagation mechanisms. It was shown that da/dN decreases strongly when the crack tip interacts with the eutectic areas. Obviously, the blocking effect of the eutectic silicon particles makes the crack leaving the straight slip-band path.

Abstract: In this work we studied the microstructure evolution due to equal channel angular pressing of Cu-2wt.%Co alloy after various heat treatments. Several subsequent passes were performed at room temperature. The microstructure was characterized using electron backscatter diffraction technique in a scanning electron microscope. Local mechanical properties were studied by means of nanoindentation experiments using a Hysitron PI85 picoindenter operated inside an electron microscope.

Abstract: This work describes an experimental procedure to measure the progressive strain localization and crystal lattice rotation within metallurgical grains. A digital image correlation software was implemented and associated with mechanical tests carried out inside a scanning electron microscope on specimens exhibiting nanometric grainy patterns. Cross-correlation analyzes between electron backscattering diffraction maps were also developed to quantify the corresponding local crystal rotation relative to the original structure. The microscale strain and rotation fields on the surface of a tensile-loaded specimen made of austenitic stainless steel 316L are presented as an illustration. Their direct spatial correlation between strain heterogeneities and the progressive activation of slip systems is put into evidence and discussed.

Abstract: Refinement of the grain diameter of the micro structure of Aluminium foil with a thickness of 300μm has been done through the ARB process up to fourth cycles with 72 layers that are proven to increase formability in micro forming a cup. Grain size was measured from the full annealed condition, of the ARB process, and the results of ARB process followed by stress relieved. Formability of the formation of a cup which is expressed as the LDR has increased from 1.87 for the material conditions of full annealed to 2.00 for the ARB process followed by stress relieved in a single step process. In addition to improved formability obtained in a cup formation, grain refinement in the microstructure can also reduce cup earing and wrinkle on the cup wall.

Abstract: In DRAM products, the copper interconnections with larger grain size are preferred for lower electrical resistance and better circuit performance. We studied the copper properties which are the evolution of the grain size, distribution of the grain, and the metal line texture formation during self-annealing. And we were able to evaluate the thermal budget in the DRAM process by performing thermal excursion stress test. We found out that the condition with self-annealing time affects copper grain size and stress migration. It has been measured by the EBSD analysis system and TOF-TEM. Compared with the conventional copper anneal process which has no time delay, the self-annealing process with time delay showed the more bamboo microstructure at dram damascene process. In addition, we observed that the self-annealing process helped enhanced thermal stress stability, which is caused by lower hillock deformation to copper top surface after a batch furnace at 400°C, N2 ambient for three times.