摘要:

This paper discusses the effects of pull rate and rotation rate on the dislocation density and residual stress distributions in Czochralski‐grown silicon crystals. A photoelastic technique was used to study the residual stress. It was found that a pull rate of 7. 62 cm/h and a rotation rate of 12 rpm yielded a nearly ideal radial stress pattern and a relatively low and constant distribution of dislocations. In general, when the dislocation density increases from the center to the periphery, and the crystal has not undergone extensive plastic flow, an optical pattern indicative of a radial stress distribution is observed. Conversely, crystals which exhibit dislocation distributions that decrease toward the periphery and have undergone plastic flow show an optical pattern which indicates a departure from a radial stress.

ISSN:0021-8979    

DOI:10.1063/1.1659763

出版商:AIP    

年代:1971

数据来源: AIP

摘要:

A new method is presented for calculating the surface energy for brittle fracture in a solid. Use is made of the knowledge of some features of the crystal dynamics as well as of the Debye, melting, and boiling temperatures of the material. Predicted values for the surface energy of a number of metals are compared with those based on the elastic theory and with the experimental ones. In particular, easy cleavage of zinc and, in contrast with recent predictions of elastic theory, the preferred plane of fracture in tungsten and beryllium are made plausible.

ISSN:0021-8979    

DOI:10.1063/1.1659764

出版商:AIP    

年代:1971

数据来源: AIP

摘要:

This analysis presents a new approach to the problem of temperature dependence of elastic constants, which leads to a simple expression. A phenomenological model is assumed to explain and estimate the temperature dependence of elastic constants. The model consists of the usual harmonic oscillator with the applied force term plus a third‐order term representing the anharmonicity of the oscillator. The state function &psgr; is evaluated in terms of the Hermitian polynomials using perturbation methods. The average mean displacement of the mass points (atoms or molecules) is obtained by using the state function and Maxwell‐Boltzmann distribution. Consequently, the expression for the elastic constant and also for the coefficient of the thermal expansion is obtained. The result is again averaged over the range of frequencies, using Debye spectrum. The final expression shows good agreement with experimental results and other theories.

ISSN:0021-8979    

DOI:10.1063/1.1659765

出版商:AIP    

年代:1971

数据来源: AIP

摘要:

Single‐phase metastable fcc Fe&sngbnd;Rh alloys have been obtained by rapid quenching from the liquid state over a wider range of compositions than formerly reported. Lattice spacings and Mo¨ssbauer spectra of Fe57of these alloys have been measured at room temperature. Both lattice parameters and isomer shifts are found to vary smoothly with rhodium concentration. These experimental findings suggest the existence of a continuous &ggr; field at high temperatures. A tentative phase diagram based on the results of the present investigation is proposed.

ISSN:0021-8979    

DOI:10.1063/1.1659766

出版商:AIP    

年代:1971

数据来源: AIP

摘要:

A technique has been developed of revealing both grown‐in and glide dislocations in nickel by etching any arbitrarily chosen crystal plane. The success of the method does not depend on decoration of dislocations and hence can be applied to the study of deformed structures without the necessity for a heat treatment. The geometric features of the etch pits are reported and their relationships to the crystallographic directions and planes of Ni are discussed. Bend tests showed a satisfactory agreement between calculated and measured dislocation densities. The etch has been employed to reveal dislocation distribution in as‐grown, annealed, and deformed crystals.

ISSN:0021-8979    

DOI:10.1063/1.1659767

出版商:AIP    

年代:1971

数据来源: AIP

摘要:

A study of the high‐pressure transformation in iron using an opposed‐anvil x‐ray diffraction apparatus and high‐pressure light metallography has shown that the 130‐kbar transformation is martensitic. The bcc and hcp phases were found to coexist over a large pressure range, and there is a large hysteresis between the forward and reverse transformation‐start pressures. A room‐temperature equilibrium pressure for the bcc and hcp phases of 107 ± 8 kbar is proposed, and discrepancies in the currentP‐Tequilibrium diagram for iron are discussed.

ISSN:0021-8979    

DOI:10.1063/1.1659768

出版商:AIP    

年代:1971

数据来源: AIP

摘要:

The work function of a polycrystalline iron filament changes somewhat abruptly in the &agr;&rlarr2;&ggr; transformation region. This change has been calculated from both electron‐emission and positive‐ion‐emission experimental data. From the electron‐emission results the difference &phgr;&ggr;− &phgr;&agr;is about 0. 09 eV, while from the positive‐ion‐emission results this difference is about 0. 06 eV.

ISSN:0021-8979    

DOI:10.1063/1.1659769

出版商:AIP    

年代:1971

数据来源: AIP

摘要:

The problem of step motion during lateral growth in solid‐solid phase transformations is considered. The present model is concerned with the case in which volume diffusion in the parent phase is the predominant contribution to the growth rate, and it is assumed that the steps do not interact appreciably. The relationships between growth rate and supersaturation are obtained from an approximate solution of the diffusion equation in a moving coordinate system. The predictions of the model are then tested against the observed behavior of steps in Al‐15 wt.&percent; Ag as reported by Laird and Aaronson, and good agreement is found.

ISSN:0021-8979    

DOI:10.1063/1.1659770

出版商:AIP    

年代:1971

数据来源: AIP

摘要:

An x‐ray diffraction technique is described which may be used to determine the composition profile of small diffusion zones as well as the diffusion‐generated substructure. Thus far, this technique is restricted to volume diffusion and has been applied in the case of a single‐phase solid solution; however, the methods may be readily applied to volume diffusion in multiphase systems. Data are presented for a system containing an 8‐&mgr; deposit of Ni on a [111] oriented single crystal of Cu. This composite was diffused at 900 °C for 45 min, 2 h, and 5 h. A Matano‐Boltzmann analysis of the composition profile gave good agreement with recently obtained diffusion coefficients. The degree of diffusion‐generated subgrain misorientation increased with annealing time and zone size up to the maximum time for our experiments. There was no evidence for the existence of nonuniform strain, and the distribution of subgrain misorientation was found to be Gaussian. Also, the widths of the Gaussian misorientation functions appear to be proportional to the lattice‐parameter gradient, although this relationship is not exact.

ISSN:0021-8979    

DOI:10.1063/1.1659771

出版商:AIP    

年代:1971

数据来源: AIP

摘要:

The Boltzmann transport equation is solved taking into consideration the skew scattering of carriers in a magnetic semiconductor. The conductivity tensor is derived and used in the study of the spontaneous Hall effect. The effect of anisotropic scattering and spin‐orbit interaction usually present in magnetic metals is accounted for.

ISSN:0021-8979    

DOI:10.1063/1.1659772

出版商:AIP    

年代:1971

数据来源: AIP