摘要:

Internal friction and elastic aftereffect measurements have been made on wire specimens of an Al‐20% Ag alloy at various stages in the precipitation process. A specimen quenched from the solid solution region and aged at 155°C shows an internal friction peak at 140°C for a vibration frequency of 0.25 cps. The relaxation strength associated with the peak is about 0.02. The peak is not greatly affected by further anneals although these anneals completely change the character of the precipitate from the initial spherical clusters of solute atoms to the plate‐like transition (&ggr;′) precipitate. In the temperature range in which clusters redissolve (reversion), however, the internal friction shows a temperature hysteresis. The activation energy associated with the internal friction peak falls in the range 25–27 kcal/mole, depending on the state of precipitation. A mechanism is suggested whereby the peak originates in a stress‐induced change in the local extent of precipitation. This behavior results from the interaction of the applied stress with the internal stresses about precipitate particles. In terms of this mechanism one can account qualitatively for the principal experimental observations.

ISSN:0021-8979    

DOI:10.1063/1.1722172

出版商:AIP    

年代:1955

数据来源: AIP

摘要:

A shadowgraphic technique has been used to measure surface motion of a series of steel plates while they deform under impact caused by ½‐in. diameter steel cylinders fired into their back surfaces at about 2800 ft/sec. The strength of the air shock produced when an initial longitudinal wave in a plate strikes the free surface of the plate has been inferred from the measured shock wave velocity in the air. The shock strength has been related to particle velocity of the surface of the plate. The results are compared to previous work involving contact explosions of small charges on plates.

ISSN:0021-8979    

DOI:10.1063/1.1722173

出版商:AIP    

年代:1955

数据来源: AIP

摘要:

The results of a phenomenological study of hollow cathodes are presented. Evidence has been accumulated to show that an oxide‐coated hollow cathode has two regions of emission with significantly different properties. These are believed to be the coated inner surface of the cavity and a deposit of crystalline material formed on the orifice edge by evaporation from the original coating. Measurements of the relative importance of the two sources have been made under various conditions.

ISSN:0021-8979    

DOI:10.1063/1.1722174

出版商:AIP    

年代:1955

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1722176

出版商:AIP    

年代:1955

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1722177

出版商:AIP    

年代:1955

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1722178

出版商:AIP    

年代:1955

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1722179

出版商:AIP    

年代:1955

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1722180

出版商:AIP    

年代:1955

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1722183

出版商:AIP    

年代:1955

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1722185

出版商:AIP    

年代:1955

数据来源: AIP