David J. Mack

Electrical resistivity and microstructural changes accompanying the isothermal decomposition of austenite in eutectoid steel

Isothermal transformation diagrams derived by optical metallography and by electrical resistance changes were compared. Incubation periods and the onset of the various transformations, as determined by these two methods, were in close agreement. However, the 100 pct transformation times that were determined by optical metallography always preceded those determined by the resistance method. The time differences between these data increased with decreasing temperature. This may be accounted for in terms of composition adjustments which are not possible to observe metallographically. The acceleration of the onset of the lower bainite reaction at temperatures approaching theMs temperature was also observed.

The isothermal transformation of a eutectoid beryllium bronze

Above the nose of the T-T-T curve the first product is fine lamellar pearlite, which subsequently transforms to a coarse pearlite, also by nucleation and growth. At lower temperatures this coarse pearlite forms directly from beta. Numerous metastable structures are formed before the pearlite reactions begin. The transformation is followed by metallographic microhardness and X-ray methods.

Slip in the intermediate phases γ-AgZn and γ-Cu-Al

Abstract Single crystals of γ-AgZn and γ-CuAl were plastically deformed by high-temperature tensile creep and constant-strain rate compression. The slip system was of the type {110}〈111〉. Duplex slip occurred in crystals oriented near the 001,011 boundary. The γ-AgZn crystals strained 5% or more exhibited considerable subgrain rotation.

Silver-Cadmium Eutectoid

The transformation of β was studied by isothermal methods. At all temperatures, the β transforms quickly to fine grained β″ which develops silver-rich striations. At higher temperatures the striations disappear, the final structure being Widmanstatten α in β′. At lower temperatures, the striated β′ is consumed by pearlite nodules of α + β′ which in turn form the Widmanstatten α in β′ The transformation is unlike any previously reported for a eutectoid.

Isothermal Transformation and Properties of a Commercial Aluminum Bronze

The transformation characteristics are found to resemble a similar binary alloy. The differences are due to the alpha iron particles. While strength properties of the isothermally transformed alloys are high, ductility is low, resulting in high notch sensitivity. The elastic modulus can be varied widely and correlates with strength. Abnormal grain growth sometimes occurs.