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Abstract: Effect of interfacial shear strength on longitudinal tensile properties for SiCf/Ti–6Al–4V composites is investigated by Monte Carlo finite element method. A two-parameter Weibull function is employed to describe random distribution of fiber strength. Fiber breakage, matrix cracking and interfacial debonding are simulated by killing the element when stress applied to element exceeds corresponding strength and releasing coupled nodes when shear stress exceeds shear strength at interfaces. The results show that tensile strength of SiCf/Ti–6Al–4V composites keeps unchanged for various interfacial shear strengths, but low interfacial shear strength is advantageous to reduce catastrophic failure. Moreover, with low interfacial shear strength, fiber breakage in the composites is more inclined to be non-coplanar. In addition, tensile strength obtained from finite element method is compared with those predicted by global load-sharing model (GLS), local load-sharing model (LLS) and conventional rule of mixtures (ROM) and is identical with that obtained from LLS. [Copyright &y& Elsevier]

Abstract: The heterogeneous precipitation of the S (Al2CuMg) phase along dislocations is investigated using high-resolution transmission electron microscopy various configurations of the S precipitate group form according to the initial dislocation morphology and no more than two S variants coexist along a single dislocation line. The most favorable combination of two S variants is observed to be variants 1 and 4 (or variants 2 and 3), and the variant selection criterion for S precipitate with the classic orientation relationship is proved to be that the dislocation line direction lies in the habit plane of the precipitate. The contribution of S precipitate groups to strengthening is evaluated by comparing the difference in total system energy increment induced by precipitate loop and the equivalent number of Guinier–Preston–Bagaryatsky zones and discrete S particles during plastic deformation. The results show that the average size of the precipitate loops as well as other kinds of precipitate groups has an important influence on the final strengthening effect. By keeping the precipitate groups below a critical size and increasing their density, the strength and thermal stability of the alloy are expected to be improved. [Copyright &y& Elsevier]

Abstract: A two-dimensional finite element model is created to investigate the effects of temperature and residual stress on transverse tensile behaviors for SiC/Ti–6Al–4V composites with square fiber array. The spring elements are used to simulate interfacial debonding when interfacial radial stress, composed of residual radial stress and radial stress introduced by the applied transverse tensile stress, reaches interfacial bonding strength. The results indicate that temperature has an obvious influence on the collapse stress of composites due to the change of matrix strength with temperature. And the higher temperature is, the lower collapse stress is. Residual radial stress can increase the applied stress required to cause interfacial debonding, but has a little influence on the collapse stress of the composites. [Copyright &y& Elsevier]

Abstract: An improved interphase layer model, which combines the interphase layer model and the spring layer model, is presented to describe the interphase of composites. The finite element model consists of the fiber, the matrix, the interphase and the spring element. The finite element model is used to model the push-out test and evaluate interface properties of composites. The results show that the interfacial shear strength of SiC/Timetal-834 is about 500 MPa. Moreover, the effects of the interphase thickness and interfacial shear strength on the peak load of the push-out test are analyzed in detail. Evaluation of interfacial properties in SiC fiber reinforced titanium matrix composites using an improved finite element model [Copyright &y& Elsevier]

Based on shear-lag method, two models for a single fiber push-out test are proposed to evaluate the interfacial shear strength of SiC fiber-reinforced titanium-matrix composites (TMCs). In the models, the effects of specimen parameters (such as specimen thickness and fiber volume fraction) on the interfacial shear strength are considered. The interfacial shear strengths of SCS-6/Ti-24-11 and SCS-6/Ti-15-3 composites are predicted using the model. The predicted results indicate that the models can be reliably used to predict interfacial shear stress of TMCs. [ABSTRACT FROM AUTHOR]

Cryorolling (CR) can effectively avoid room temperature rolling cracking of high-strength aluminum alloy. In this work, solution-treated bulk Al 7085 alloy samples were subjected to CR and room temperature rolling (RTR), respectively. When the deformation was 70%, the RTR sample was broken, while the CR one still had no cracks when the deformation was up to 90%. Consequently, the microstructure and mechanical properties of the CR samples before and after ageing treatment were investigated. The results show that after the solution-treated bulk Al 7085 alloy samples were cryorolled, the yield strength (YS) and the ultimate tensile strength (UTS) were increased by 74% and 31%, respectively. However, the elongation to failure (EtF) was decreased. After the subsequent 100 °C/20 h peak ageing (PA) treatment, the YS and UTS can be further increased by 14% and 10%, respectively, and the EtF was increased by 39% compared with that of the CR samples. After PA treatment, nanosized GP zones and η′ precipitates were precipitated. Precipitation strengthening is the main contributor to the strength enhancement of CR samples after PA treatment, which can not only compensate for the reduction caused by the decrease in dislocation density but also improve the strength of the material. • Al 7085 alloy was processed by cryorolling and subsequent ageing treatment. • Strength and ductility of the cryorolled sample can be simultaneously improved after peak ageing treatment. • The aged sample contains nanosized GP zone and η′ precipitates. • Precipitation strengthening is the main contributor for strength enhancement of the cryolled + peak aged sample. [ABSTRACT FROM AUTHOR]

Cryorolling (CR) can effectively avoid room temperature rolling cracking of high-strength aluminum alloy. In this work, solution-treated bulk Al 7085 alloy samples were subjected to CR and room temperature rolling (RTR), respectively. When the deformation was 70%, the RTR sample was broken, while the CR one still had no cracks when the deformation was up to 90%. Consequently, the microstructure and mechanical properties of the CR samples before and after ageing treatment were investigated. The results show that after the solution-treated bulk Al 7085 alloy samples were cryorolled, the yield strength (YS) and the ultimate tensile strength (UTS) were increased by 74% and 31%, respectively. However, the elongation to failure (EtF) was decreased. After the subsequent 100 °C/20 h peak ageing (PA) treatment, the YS and UTS can be further increased by 14% and 10%, respectively, and the EtF was increased by 39% compared with that of the CR samples. After PA treatment, nanosized GP zones and η′ precipitates were precipitated. Precipitation strengthening is the main contributor to the strength enhancement of CR samples after PA treatment, which can not only compensate for the reduction caused by the decrease in dislocation density but also improve the strength of the material. • Al 7085 alloy was processed by cryorolling and subsequent ageing treatment. • Strength and ductility of the cryorolled sample can be simultaneously improved after peak ageing treatment. • The aged sample contains nanosized GP zone and η′ precipitates. • Precipitation strengthening is the main contributor for strength enhancement of the cryolled + peak aged sample. [ABSTRACT FROM AUTHOR]