As a typical ceramic matrix composite （CMC）, SiC_f/SiC composite has enormous potential for application in the aerospace field because of the excellent properties such as high specific strength, high temperature resistance, oxidation resistance and good thermal shock resistance. The interphase between fiber and matrix plays a crucial role for protecting fibers, transmitting load and deflecting cracks, resulting in the pseudo-plastic fracture characteristics of SiC_f/SiC composites. The design scheme of interphase significantly affects its microstructural properties, thereby affecting the macroscopic mechanical properties and damage failure modes of SiC_f/SiC composites. In recent years, nano/micro fabrication techniques based on the focused ion beam （FIB）and nano/micro mechanical testing methods based on the nanoindentation are the effective methods to analyze and extract the interphase properties of SiC_f/SiC composites. The existing design schemes of interphase and the influence of interphase properties on toughening mechanism are reviewed. And also the application conditions, advantages and disadvantages of small-scale mechanical testing techniques including single fiber push-out/push-in and micropillar compression are summarized. Finally, the development trend for the research of CMC interphase properties are prospected: further standardizing the testing methods, building a high-temperature testing platform and modeling of testing data.

An ultra-fine grained (UFG) Mg-1Zn-0.2Ca-1.0MgO composite with an average grain size of 0.49 µm as well as an excellent combination of yield strength (379 MPa) and ductility (10.1%) was produced by one-step extrusion. Subsequent heat treatment at 200 ℃ for 30 min further improved its yield strength to 420 MPa and elongation to 12.1% with a slight grain growth to 0.76 µm. Microstructure observations revealed that the precipitation of high number density of Ca₂Mg₆Zn₃ phase was the main reason for the enhanced strength after ageing treatment. Grain coarsening and recovery of dislocations during ageing improved the work-hardening capability of the extruded sample, leading to improved ductility. Our work provides a pathway for the mass production of strong and ductile Mg-based materials without excessive addition of alloying elements.

Twinning and detwinning behavior of a commercial AZ31 magnesium alloy during cyclic compression–tension deformation with a total strain amplitude of 4% (±2%) was evaluated using the complementary techniques of in-situ neutron diffraction, identical area electron backscatter diffraction, and transmission electron microscopy. In-situ neutron diffraction demonstrates that the compressive deformation was dominated by twin nucleation, twin growth, and basal slip, while detwinning dominated the unloading of compressive stresses and subsequent tension stage. With increasing number of cycles from one to eight: the volume fraction of twins at -2% strain gradually increased from 26.3% to 43.5%; the residual twins were present after 2% tension stage and their volume fraction increased from zero to 3.7% as well as a significant increase in their number; and the twinning spread from coarse grains to fine grains involving more grains for twinning. The increase in volume fraction and number of residual twins led to a transition from twin nucleation to twin growth, resulting in a decrease in yield strength of compression deformation with increasing cycles. A large number of <c>-component dislocations observed in twins and the detwinned regions were attributed to the dislocation transmutation during the twinning and detwinning. The accumulation of barriers including twin boundaries and various types of dislocations enhanced the interactions of migrating twin boundary with these barriers during twinning and detwinning, which is considered to be the origin for increasing the work hardening rate in cyclic deformation of the AZ31 alloy.