Analysis on the process of ZAO films by DC magnetron reactive sputtering

The ZAO (ZnO:Al) thin films were prepared by DC reactive magnetron sputtering technique. The relationship between the process parameters and the organizational structure,optical and electrical properties was studied. Through optimizing the process parameters,an optimal preparation parameter can be obtained. Using the optimal parameters to prepare the ZAO thin films,the resistivity of the ZAO film is as low as 4.5×10-4 Ω·cm and the average transmissivity in the visible region is around 80%,the optical and el...     

Low temperature anneal-embrittlement of (Fe0.99Mo0.01)78Si9B13 amorphous ribbon: boron segregation?

Abstracts are not published in this journal     

Simulating a double casting technique using level set method

Level set method is an appropriate mathematical tool for solving two-phase flow problems. It is used here for the first time to track the interface evolution during the process of casting a second alloy into mold, partly displacing the first to achieve a casing with a different alloyed skin. Projection method for Navier–Stokes equations was adopted and the algorithm was implemented in finite element method. The numerical example shows that though in those cases where the layer of liquid metal above is lighter than that below, the interface is not always stable for density ratios less than one of the two liquid metals. The stability of the interface is sensitive to the density ratio and inlet velocity and relatively insensitive to the viscosity ratio or other parameters. It is believed that level set method has potential to be further used in real double casting processes.     

Increasing the Fracture Toughness of Alumina Based Ceramics by Oxidation-Induced Surface Stresses

Abstracts are not published in this journal This revised version was published online in November 2006 with corrections to the Cover Date.     

CYCLIC DEFORMATION OF A DIRECTIONALLY SOLIDIFIED COBALT-BASE SUPERALLOY

An investigation has been carried out on the cyclic deformation and changes in microstructure of a directionally solidified cobalt-base superalloy. The tests are conducted at 700 °C and 850 °C in air under different total strain amplitudes. The alloy tested at 700 °C exhibits an initial hardening, a short saturation stage and an evident secondary hardening, while the alloy at 850 °C suffers continuous cyclic hardening until fracture. TEM examinations indicate that the initial hardening of the alloy at 700 °C is caused by the pile-ups of dislocations and stacking faults at the stacking fault intersections, while the stress saturation is due to the weakening of obstacles against the dislocation movement. The secondary hardening has a contribution from the formation of sessile dislocation tangles. The early stage of continuous hardening of the alloy at 850 °C is related to the pile-ups of dislocations and stacking faults at the intersections, and the later stage is controlled by the interaction between precipitates and dislocations.     

FATIGUE CRACKING POSSIBILITY ALONG GRAIN BOUNDARIES AND PERSISTENT SLIP BANDS IN COPPER BICRYSTALS

In this paper, the fatigue cracking possibility in different kinds of copper bicrystals with large-angle grain boundaries (GBs) and copper multicrystals containing some low-angle GBs are compared. The results showed that the fatigue cracks, in the copper bicrystals, always nucleated firstly along GBs no matter whether the GBs are perpendicular or parallel to the stress axis. Whereas, for the copper multicrystals containing low-angle GBs, the persistent slip bands (PSBs) are always the preferential sites to initiate fatigue cracks no matter whether low-angle GBs are perpendicular or parallel to the stress axis.
Additionally, the fatigue lives of the GBs, and the [1¯23] and [3¯35] grains in the [1¯23] ⊥ [3¯35] and [5¯913] ⊥ [5¯79] bicrystals were measured at different cyclic stresses and strain amplitudes. The results show that intergranular fracture always occurred prior to transgranular fracture in those bicrystals. The fatigue lives increased in the order of the GB, the [1¯23] and the [3¯35] grains in the [1¯23] ⊥ [3¯35] bicrystal under cyclic tension–tension loading. On the other hand, the fatigue life of the GB in the [5¯913] ⊥ [5¯79] bicrystal is about two to three times higher than that in the [1¯23] ⊥ [3¯35] bicrystal. Based on these experimental results from the copper bicrystals and multicrystals, it is indicated that the possibility of fatigue cracking increased in the order of low-angle GBs, PSBs and large-angle GBs. It is suggested that both the PSB–GB mechanism and the step mechanism required for GB fatigue cracking were questionable, and the interaction modes of PSBs with GBs may be more important for intergranular fatigue cracking.