Calculations of specific heat vs temperature curves corresponding to measurements with finite heating rates have been carried out for alloys under various initial conditions utilizing the pair approximation of the Path Probability method of time dependent cooperative phenomena and are compared with experiments on Mg3Cd, FeCo, and Cu3Au. New experiments on Mg3Cd suitable for comparison are also presented here. The main emphases of the comparisons are (1) the appearance of a specific heat subpeak below the main specific heat peak at Tc for well annealed alloys, (2) the shift of the subpeak by a change of the heating rate, (3) the appearance of a specific heat dip for alloys quenched from higher temperatures, and (4) the appearance of two specific heat dips for highly disordered alloys quenched from above the critical point of order–disorder. Good qualitative agreement of theory and experiment is obtained in each of these four categories.
Ana~sis of the transition behaviour of mild steel in Charj)y impact test was made over a temperature range of 100°-196°C, observing Ihe relationshill between load and time during impact. Besides the standard V-notch sj)ecimens, the brittle boundary layer specimens that were prepared by carburiz ing the free surface layers of the standard sp ecimens were used. As a result, the transition in Charpy impact test was found to be divided into six tem/)erature regions. The fracture structure characteristics for each of those transition regions were examined by means of electron microscopic observation. Of the usual transition temperatures, Charpy-V 15 ft-lb energy, Charj)y-V 0% shear, and Charpy-V 15 mil lateral expansion were found to be the yield point fracture criteria; CharjJy-V 30-35ft-lb energy or CharjJY-V 25% shear, on the other hand, was identified as the initiation (ductility) transition temjJerature, at which, no ductile crack being able to j"o-(lagate after the maximum bending load has bee/l attained, raj)id transition to brittle fracture occurs,' this temp erature was seen to correspond to the NDT of NRL drol) weight test. Another important transition temj)erature foun d was the cleavage initiation temj)erature at which cleavage frac ture aj)pears first in the load/time curve; this temj)erature coincided with the near~ 100% cleavage ji-acture apj)earance teml)erature in the brittle boundary layer specimCl7s. This temj)erature gave a measure of estimating the brittle crack jJrojJagation arresting temperature of large sp ecimen test. Furthermore, an aitemj)t was made to obtain fracture toughness value, G e , by the brittle boundary layer s/Jecimens. Some agreement with the results from the temperature gradient type ESSO test was obtained. Ge's relative to the onset and the arrest of the brittle crack jJrojJagation were determined and their significances discussed. * ** Yield loads at this low temperature reg ion in Fig. 2 were determined by Charpy specimens with their n otch on th e compressed, rather than on the tensile, side to preven t fracture before general yielding. *** * Some ductility, such as , for example, the plastic hinge shown in Fig. 1, was still observed even at temperatures as low as this; thi s is clue probably to the effect of strike of the hammer.
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