Experimental Investigations on the Grinding Temperature of the Superhard Grinding Wheel with Ordering Abrasive Pattern

In the area of grinding, ordering the abrasive gains is one of the key ways to improve the grinding wheel performance. In this article, the experimental investigations on the grinding temperature were carried out including using the superhard abrasive grinding wheel with phyllotactic, matrix, dislocation and disordered configuration, the temperature distribution of the grinding workpiece surface and the effects of grinding parameters on the temperature of workpiece surface have been obtained. The experimental results showed that the grinding temperature can be reduced efficiently by choicing the grinding wheel with abrasive phyllotactic pattern.

Characterizing Precipitation Defects in Nickel Based 718 Alloy

In the present study we examine the crystallographic structure of the , ’’ and  phases present in nickel base 718 alloy. The chemical ordering of Nb atoms and possible planar faults that may be observed in ’’ precipitates are detailed. High resolution transmission electron microscopy (HRTEM) observations of various faults are reported. The decomposition of a matrix dislocation to form a locked V shaped configuration is shown. The observation along [110] type direction allows to identify the type of defect, which is observed as a pure geometric stacking fault.

HREM Study of the Strain Field Induced by the Entrance of a Matrix Dislocation within the Coherent Twin GB in Ge.

Strains around a constricted matrix dislocation in a coherent twin grain boundary in germanium is measured by a combination of high-resolution electron microscopy and geometric phase analysis. Whilst strains in the grains on either side of the twin boundary agree closely with the isolated dislocation case, significant additional strains are localized at the boundary plane. By comparing the stresses and strains across the boundary plane, values for the elastic modulus of the twin boundary are determined. They are found to exhibit a drastic decrease as compared to the bulk and this is interpreted in terms of the non-equilibrium configuration of the boundary.

A Viscoplastic Constitutive Model for 63Sn37Pb Eutectic Solders

In the present study, a new constitutive model for eutectic solders (63Sn37Pb) is proposed. Grain sizes and phase sizes are considered as the coarsening is one of the main reasons for failure of solder joints. The present model has been developed based on the combination of grain boundary sliding and matrix dislocation deformation mechanisms in order to describe a thermo-mechanical behavior of eutectic solders. Internal stress tensors are also introduced to describe the transient behaviors during the tensile test and first stage creep. A series of tensile, creep, and creep recover tests were conducted at temperature range from −10 to 100°C. The specimens with two different phase sizes were tested. Good agreements were obtained between the experimental results and the model.

Determination of Residual Strains in an Al-SiCw Composite Using CBED

It is well established that large stresses may be introduced into Al-SiCw composites by thermal cycling. Due to the large difference in thermal expansion of Al and SiC, a temperature change of ~200°C is sufficient to generate dislocations in the matrix. Dislocation production does not relieve all of the stress and residual strains, which are slightly below the yield point, can remain in the matrix. Although these residual strains will influence both the aging characteristics of the matrix and mechanical response of the composite, very few experimental measurements have been made of the local residual strains in Al-SiCw composites.The purpose of this investigation was to determine the magnitude of residual strains around individual whiskers in an Al-10 vol.% SiCw composite, which was annealed at 505°C and quenched to room temperature. Convergentbeam electron diffraction (CBED) was used for this investigation since all the information in a CBED pattern originates from a small area defined by the incident probe.

Evidence from in situ TEM straining studies for the mechanism of transfer of slip across a grain boundary

The bulk mechanical properties of a material will primarily be determined by the integrity of the grain boundaries which depends on the local chemistry and the boundary structure. Changes in the composition of the boundary may affect the strength of the atomic bonds through a redistribution of the electrons; this effect has been predicted from theoretical calculations1 but not determined experimentally. The structure of the boundary will be determined by the mismatch between the adjoining grains and it will affect the mechanism by which strain is transferred through the boundary. From static observations of the interaction between matrix and grainboundary dislocations the following scenario has been constructed for the transfer process through random boundaries; The interaction between the incoming matrix dislocation and those in the grain boundary cause the emission of a dislocation from a grain-boundary dislocation source into the adjacent grain. To preserve the contiguity of the grain boundary a residual dislocation will be created within the grain boundary.