The Deformation of Pure Aluminium as Non-isoaxial Bicrystals(Metallurgy)

The strength of pure aluminium non-isoaxial bicrystals composed of differently oriented component crystals was investigated. By calculating a "grain boundary strength" Δσ, the following results were obtained. The grain boundary strength was found to depend on the vector relationship of the slip systems expressed by the compatibility condition and by dislocation pile-up at the grain boundary. The larger the value of the "maximum orientation difference factor" N the lower becomes Δσ_. The bicrystal specimens with largest N showed negative Δσ_. A parabolic relation was found for the strain dependence of the grain boundary strength

Anisotropies and Low-temperature Annealing Effect in Cold-rolled Nickel-Silver Alloy

The changes in hardness, elastic modulus and bending deflection with rolling reduction and with low-temperature annealing of nickel-silver were measured on the specimens cut parallel and transverse to the rolling direction of the sheet, and the results were considered in relation to the rolling structure. The anisotropies become more remarkable as the rolling reduction exceeds 50 per cent, and, in this region, the measured values are always higher in the transverse than in the other direction. This may be due to the development of the rolling texture and to the appearance of the flaw-like strain markings in the transverse direction. The low-temperature annealing makes the values of hardness and elastic modulus increase, and the maximum values are, in either case, obtained by heat-treatment at 350℃. Also, the larger the rolling reduction is, the higher the increasing ratio becomes. The change in hardness due to low-temperature annealing is larger as the grain size reduces, whereas the change in elasticity is hardly affected by the grain size. The anneal-hardening at each temperature does not show the two-stage hardening which has been observed in α-brass sheet, but shows a simple and smooth process. No difference in microstructure can be observed between as cold-rolled and as anneal-hardened state, although, in the previous work on α-brass, some structural changes thought to be a kind of polygonization were recognized after low-temperature annealing. The results of bending test correspond with those of elastic modulus

Rolling Structure and Elastic Anisotropy of Cold-Rolled α Brass

The change in the elasticity of 70/30 brass with rolling reduction was measured in three directions, namely, parallel, diagonal and transverse to the rolling direction. The whole reduction range up to 90 per cent was divided into three stages, according to the types of the anisotropy. At low reductions up to about 40 per cent, one of the three directions, the parallel direction gave the maximum elasticity value, showing a peak at the reduction of 20～30 per cent. Especially in a coarse-grained material, this change seemed to be due to a geometrical inhomogeneity of strain distribution found at the grain boundaries or at the band-shape regions existing along the rolling direction rather than to a crystallographic directionality. At high reductions beyond 70 per cent, the developments of the rolling texture and flaw-like strain markings resulted in a high elasticity value in the transverse direction, and a low one in the other two. The intermediate reduction might probably show a stage transitional from one to the other mentioned above. The abnormal work-hardening previously pointed out by others was also discussed in relation to the present results

Multiplex Heat-treatment-The Possibility for Improving the Treatment of Low-temperature Annealing

The elastic modulus (expressed by the square of the fundamental resonance frequency, f_0^2) of cold-rolled 70/30 brass rose with the rise of heat-treating temperature below recrystallization. In addition, when the specimen was sufficiently heat-treated at high temperatures, the modulus increased further with re-heat-treatment at lower temperatures. A similar effect was also seen in hardness change. The effect of the multiplex heat-treatment was also precisely examined by changing the treating time and temperature. Thus, it was shown that only in the specimens heat-treated enough to reach the second anneal-hardening stage, the effect revealed itself. The phenomenon was thought to be available for improving the usual low-temperature annealing technique, and its mechanism was interpreted in relation to the behaviour of lattice imperfection and solute atom

Guided Lock of a Suspended Optical Cavity Enhanced by a Higher Order Extrapolation

Lock acquisition of a suspended optical cavity can be a highly stochastic process and is therefore nontrivial. Guided lock is a method to make lock acquisition less stochastic by decelerating the motion of the cavity length based on an extrapolation of the motion from an instantaneous velocity measurement. We propose an improved scheme which is less susceptible to seismic disturbances by incorporating the acceleration as a higher order correction in the extrapolation. We implemented the new scheme in a 300-m suspended Fabry-Perot cavity and improved the success rate of lock acquisition by a factor of 30

Superconducting Properties and Microstructure in Dilute Copper Alloys Containing Small Amounts of V_3Ga Particles(Metallurgy)

The superconducting properties (T_c and J_c) were investigated by the resistivity measurement, and the structure was observed by a transmission electron microscopy in the dilute copper alloys containing small amounts of V_3Ga particles prepared by quenching from the liquid state and aging. No superconductivity could be observed at 4.2 K in as-quenched and/or in overaged samples. The highest T_ (=12.5 K), T_ (=9.6 K), and J_c (=525 A/cm^2) were obtained by aging at 700℃ for 96 h and corresponded with the structure of fine V_3Ga precipitates dispersed homogeneously in the copper matrix. Therefore, it is concluded that superconductivity in these alloys results from the superconducting path due to the proximity effect of the superconducting V_3Ga particles

Grain Boundary Fracture of α Brass Bicrystals at an Intermediate Temperature Range

Deformation and grain boundary fracture behaviours of α brass bicrystals were examined. The results are summarized as follows : (1) The temperature dependence of the ductility of α brass bicrystals accompaning intergranular fracture is similar to that observed in α brass poly-crystals. (2) The transition from transgranular to intergranular fracture starts at about 470 K and again a transgranular fracture appears at about 770 K : i. e., the inter-granular fracture occurs in the temperature range of 470 to 770 K. It is note worthy that the lower transition temperature (470 K) corresponds to the onset of the inverse temperature dependence of yield stress. Also, the temperature at which the minimum value of ductility reveals coincides with that at which a peak in the yield stress appears. (3) Though the intercrystalline fracture accompanies the separation at the grain boundary plane macroscopically, it is a ductile fracture in the neighbourhood of grain boundary microscopically. Thus, apparent intergranular fracture seems to be caused by the coalescence of micro cleavage cracks along {111} planes, which are induced by the stress concentration due to dislocation pile-ups. (4) From those observations mentioned above, it is clear that the dynamic strain aging behaviour plays an important role in the intergranular fracture of α brass bicrystals