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Thermal interface materials (TIMs), which are recently being used in high-power and new-generation materials, improve thermal stability at high temperatures because of the formation of intermetallic compounds. In this study, Cu-type Ga-based TIM solder has been selected to investigate the interface reaction of Ga-based thermal interface materials after curing, annealing, and reflow. During the curing process, liquid Ga diffuses through the X-alloy and reacts with Cu, resulting in the formation of the CuGa2 phase. With the increase of annealing time, the area fraction of CuGa2 and Cu9Ga4 decreases by 38% and increases by 44% because of the further diffusion of Cu into Ga, respectively. During reflow, the diffusion of Cu atoms into Ga leads to the formation of the solid solution of Cu and Ga. Meanwhile, the melted X-alloy reacts with Cu and forms Cu6X5. [ABSTRACT FROM AUTHOR]

A raw electron backscatter diffraction (EBSD) signal can be empirically decomposed into a Kikuchi diffraction pattern and a smooth background. For pattern indexing, the latter is generally undesirable but can reveal topographical, compositional, or diffraction contrast. In this study, we proposed a new background correction method using polynomial fitting (PF) algorithm to obtain clear Kikuchi diffraction patterns for some applications in nonconductive materials due to coating problems, at low accelerated voltage and at rough sample surfaces and for the requirement of high pattern quality in HR-EBSD. To evaluate the quality metrics of the Kikuchi patterns, we initially used three indices, namely, pattern quality, Tenengrad variance, and spatial–spectral entropy-based quality to detect the clarity, contrast, and noise of Kikuchi patterns obtained at 5 and 15 kV. Then, we examined the performance of PF method by comparing it with pattern averaging and Fourier transform-based methods. Finally, this PF background correction is demonstrated to extract the background images from the blurred diffraction patterns of EBSD measurements at low kV accelerating voltage and with coating layer, and to provide clear Kikuchi patterns successfully. [ABSTRACT FROM AUTHOR]

In this study, we reviewed the definitions of indentation strain and stress proposed from earlier studies and then calculated indentation strain–stress curves according to 20 combinations of five indentation strain definitions and four indentation stress definitions. The finite element method was applied to predict the load–displacement curves and the force–displacement for spherical nanoindentation and tensile test, respectively. Thus, the load–displacement data were used to determine indentation strain–stress curves, which were compared with the stress–strain curve, obtained from the tensile test simulation. Comparing with the tensile stress–strain curve, three combinations of σX − ɛK, σO − ɛA, and σH − ɛM reveal better fitting curves than the other combinations, where the subscripts of X, K, O, A, H, M are denoted as Xu and Chen (J Mater Res 25:2297-2307, 2010), Kalidindi and Pathak (Acta Mater 56:3523-3532, 2008), Oliver and Pharr (J Mater Res 7:1564-1583, 1992, J Mater Res 19:3-20, 2004), Ahn and Kwon (J Mater Res 16:3170-3178, 2001), Hill et al. (P R Soc Lond 423:301-330, 1989), and Milman et al. (Acta Metal Mater 41:2523-2532, 1993), respectively. The limitation of the indentation strain is at 0.06, 0.03, and 0.01 for combinations of σX − ɛK, σO − ɛA, and σH − ɛM. The stress constraint factor (called the ratio of mean contact pressure to tensile stress) for combinations of σX − ɛK, σO − ɛA, and σH − ɛM is 3.4, 3.4, and 2.6 to obtain the optimized fitting indentation stress–strain curves with the parameter n of the power law of 0.306, 0.248 and 0.173, which reveal the deviation of 43.0%, 15.9%, and 19.2%, respectively, in comparison with that of the tensile flow curve. Considering the best fitting curve by the combination of σO − ɛA, together with the stress constraint factor ψ of 3.4, the fitting parameters of n and K are 0.248 and 588.56 corresponding to the deviation of 15.9% and 7.7% in terms of these parameters in the tensile flow curve. [ABSTRACT FROM AUTHOR]

This study investigated the effect of cooling rate on the formation of carbide bands in hot-rolled SUJ2 steel after spheroidization. The metallographic microstructure was observed under an optical microscope and a scanning electron microscope with an electron backscatter diffractometer, and the distribution of the chemical composition was analyzed using a field emission electron probe. Experimental results show the formation of carbide banding and the effect of cooling rate. Cr segregation occurs in carbide banding, in which C content increases after austenitization and spheroidization. The area fraction of carbide in the band region is larger than that in the normal region. Increasing the cooling rate can restrain the diffusion of C into the Cr microsegregation band. The formation of carbide banding can be avoided at a high cooling rate. This phenomenon may aid in quantifying the processing parameter of the cooling rate to improve the quality and the lifetime of bearings for bearing steels. [ABSTRACT FROM AUTHOR]

The effect of manganese sulfide (MnS) inclusions on the machinability of free-cutting steel is based on their morphology, size and distribution. Furthermore, the plasticity of MnS is high during the hot working caused different characterization of MnS. In this study, the deformation behavior of MnS in 1215MS steel after a thermomechanical process was investigated at 1323 K. The microstructures of MnS inclusions were characterized by optical microscopy, scanning electron microscopy, energy-dispersive spectrometry, and electron backscattering diffraction (EBSD). As the thickness reduction of the inclusions increased from 10 to 70%, their average aspect ratio increased from 1.20 to 2.39. In addition, the deformability of MnS inclusions was lower than that of the matrix. The possible slip systems of A, B, C, and D plane traces were 1¯01¯1¯01,101¯101,011011¯, and 11011¯0. Furthermore, the EBSD measurements suggested that slip planes in MnS inclusions occur on {110} planes. [ABSTRACT FROM AUTHOR]