The molecular dynamics method is used to simulate microcrack healing during heating or/and under compressive stress. A center microcrack in Cu crystal could be sealed under a compressive stress or by heating. The role of compressive stress and heating in crack healing was additive. During microcrack healing, dislocation generation and motion occurred. If there were pre-existed dislocations around the microcrack, the critical temperature or compressive stress necessary for microcrack healing would decrease, and the higher the number of dislocations, the lower the critical temperature or compressive stress. The critical temperature necessary for microcrack healing depended upon the orientation of crack plane. For example, the critical temperature of the crack along (0 0 1) plane was the lowest, i.e., 770K.

In this letter, we report on delayed fracture of lead zirconate titanate ceramics with a Zr/Ti ratio of 52/48(PZT-5) ferroelectric ceramics in silicon oil under sustained electric field, and that in silicon oil or moist atmosphere under sustained mechanical load. The experimental results show that sustained electric fields may cause delayed fracture of PZT-5 ceramics and there is a threshold field for the delayed fracture. The threshold electric field is less than one third of the critical electric field to cause instant fracture and is also half of the coercive field of the PZT-5 ceramics.

Powder compacting processwas employed to fabricate nanocrystalline Cu-Zn alloy layer on the surface of coarse-grained copper matrix. The tribological behaviors of nanocrystalline surface layer after annealing in air were investigated. Sliding wear tests were performed on a pin-on-disk test machine under dry conditions. The morphologies and element chemical states of the worn surfaces were examined with scanning electron microscopy (SEM) and X-ray photoelectron spectrometer (XPS), respectively. It was found that 300℃ annealed nanocrystalline surface layer presented optimum mechanical and tribological properties. The 300℃ annealed nanocrystalline surface layer showed remarkably high load-bearing capacity. A tribo-surface film almost covering entire worn surface was observed at applied load range from 60 to 160 N. This tribo-surface film was found to comprise elements from both the sliding counterparts. XPS analysis revealed the enrichment of nanocrystalline ZnO in the tribo-surface film, which can contribute to reduce friction coefficient and form a more steady and long life tribo-surface film.

Interaction between superstructures and grain boundary in graphite has been investigated by STM. Through scanning for several times against the step of a terrace on the graphite substrate, a monolayer with a grain boundary can be torn apart from the terrace and rotated by a known angle 56.4

The nucleation and propagation behaviors of cracks in CuNiAl shape memory alloy were observed using in situ technique under atom force microscope (AFM). The results indicated that,in CuNiAl shape memory alloy,the martensitic transformation first occurred at crack tip upon loading,and then the microcrack nucleated and propagated along martensite interface. The slip bands appeared only after considerable crack propagation. After that,the crack usually propagated alternately along martensite interface or slip bands.