X-ray examination of certain copper-zinc alloys at elevated temperatures

Abstract

This investigation is a continuation of the word on copper-zinc alloys reported in previous papers. Our previous measurements were made on quenched alloys, and it was assumed that the conditions prevailing at any temperature at the moment of quenching were retained in the quenched samples. In the present word an attempt is made to investigate the validity of this assumption by examining the alloys at the actual temperatures of annealing. Attention is directed mainly to the β-phase in tire pure region and in the mixed regions on either side of the pure phase. It was hoped that such measurements might also throw more light on the nature of the β-transformation. Apparatus and Method of Experiment . The precision camera was the same in principle as that previously used and described, with modifications in deign for high temperature word. It was made entirely of invar except that three silica rods connected the portion of the drum carrying the film to that carrying the sample. By this device the one part was well insulated thermally from the other. In order to take photographs in vacuo , the camera was fitted into a brass box with a removable lid and water-cooled sides; inside the box, the heater, consisting of "Kanthal" resistance wire embedded in alundum cement, was mounted. To hold the sample, which was in the form of fine filings on thin foil, against the camera frame, a thin sheet of copper foil was used. This was anchored with insulating porcelain beads and wire springs to the camera frame carrying the film. To minimize the heat passing from the sample to the camera frame, a thin sheet of mica of definite thickness was used around the slot over which the sample was placed. The sample was heated by bringing the heater, shaped to the contour of the camera frame, into close contact with a similarly shaped copper sheet about 1⋅5 mm. thick, into which the "hot" junction of one thermo-couple was silver-soldered; this in turn pressed against the foil on which the sample was mounted. Leads for the thermo-couple pyrometers—one to measure the approximate temperature of the sample photographed and the other to measure the camera temperature near tire film—passed through insulated plugs in one side of the box. On the opposite side, leads to the heater were similarly inserted. An outlet for exhausting the box completed the construction.