G.M. Zhao

A review on the research progress of push-out method in testing interfacial properties of SiC fiber-reinforced titanium matrix composites

Experimental analysis of single-fiber push-out for SiC fiber-reinforced titanium matrix composites (TMCs) is complicated by the incorporation of large thermal residual stresses, strong chemical bond of the fiber/matrix interface and matrix plastic deformation. This paper summarizes the development of push-out test and the characteristics of push-out test for TMCs such as crack initiating at the bottom face and theoretical analysis of the test. Moreover, it deeply analyzes the progresses of interfacial shear strength and fracture toughness, and work focus is pointed out in future.

Grain refinement and texture evolution during high precision machining of a Ni-based superalloy

Abstract The grain refinement and texture evolution in the surface gradient microstructure of a Ni-based superalloy induced by high speed machining was studied in this research. The direct evidence of grain refinement induced by dislocation–twin interaction was revealed and the detailed grain refinement process was summarised as deformation twinning, dislocation-twin reaction, localied thinning of nanotwin lamellae and final fracture. The underlying dislocation–twin interaction mechanism was elucidated from the crystallographic perspective. Using electron backscatter diffraction and precession electron diffraction techniques, a multiscale texture analysis covering undeformed coarse grain region, ultrafine grain region and nanograin region was carried out. The texture evolution with decreasing depth to the machined surface was identified as cube in the bulk interior and a mixture of rotated cube {0 0 1}<1 1 0>, cube {1 0 0}<0 0 1>, copper {1 1 2}<1 1 1 > and Goss {1 1 0}<0 0 1> textures in the topmost 1.3-μm-thick nanograin layer. The intrinsic thermomechanical effects of high precision machining are responsible for crystallographic texture transformation.

Effect of Hot Isostatic Pressing Parameters on the Microstructures and Grain Growth Behavior of the Matrix of SiCf/Ti-6Al-4V Composites

Abstract The SiC f /Ti-6Al-4V composites were fabricated by the matrix-coated fiber (MCF) process under two different hot isostatic pressing (HIP) processing parameters. Both microstructural characteristics and grain growth behavior in the matrix were investigated based on a combination of experimental observations and theoretical predictions. The main microstructural characteristics including matrix component phases and their corresponding chemical composition, morphology and volume fraction were systematically examined using EDS and SEM analyses, providing valuable insight into understanding the matrix microstructural evolution during consolidation processing from initial Ti-6Al-4V matrix-coated fibers (MCFs) to the final SiC f /Ti-6Al-4V composites. A dynamic recrystallization (DRX) model coupled with Lifshitz-Slyosov-Wagner (LSW) theory were also used to predict the grain growth occurring in the matrix during consolidation processing. Correlation between the theoretical predictions and experimental results were also discussed.

Microstructure and Grain Growth of the Matrix of SiC f /Ti-6Al-4V Composites Prepared by the Consolidation of Matrix-Coated Fibers in the α + β Phase Field

Both the microstructural characteristics and the grain growth of the matrix materials in the SiCf/Ti-6Al-4V composites were investigated by means of experimental tests coupled with theoretical assessment. A very fine matrix microstructure was obtained in the SiCf/Ti-6Al-4V composites that were prepared by the consolidation of matrix-coated fiber (MCF) in the α+β phase field. During a fabrication process through the MCF method, the matrix microstructure after consolidation processing will evolve from the columnar crystals to a fully-lamellar microstructure. The experimental results especially the grain sizes of matrix microstructure were reasonably explained based on theoretical calculations.