A HOT WORKABILITY TESTING SYSTEM AND ITS APPLICATION TO SOME FCC ALLOYS

A hot workability testing apparatus has been designed and constructed. The system is composed of four major elements: (i) a closed loop servo controlled hydraulic testing machine, with programmable and custom-made control components; (ii) high-temperature tooling and radiant heating furnace for isothermal test conditions; (iii) a test specimen transfer device for ease of testing and rapid quenching; (iv) computerized data acquisition and reduction system. Isothermal, uniaxial compression tests are performed for flow stress determination, as well as upset and bend tests for workability evaluation. Test temperatures to 1200(DEGREES)C may be achieved, along with constant strain rates up to 20 sec.('-1) for both compression and bend tests. Maximum force is 160 kN. Specimens can be quenched within 0.5 sec. to permit the study of the microstructures developed during hot deformation. In both compression and bending, interrupted deformation schedules can be programmed. Change of rate tests to measure strain rate sensitivities are also possible.;The capabilities of the system are illustrated by results obtained on MP35N (35% Co, 35% Ni, 20% Cr and 10% Mo) and ETP Copper. In both materials, within the ranges studied, increasing the strain rate strongly delays the occurrence of fracture in bending and upset. The fracture behavior of MP35N in plane strain bending in the range of temperatures between 1000-1200(DEGREES)C and strain rates between 0.01-10 sec.('-1) is described in some detail, and is related to the interaction between deformation mode and microstructural evolution during hot deformation. Observations in ETP Copper are also discussed in these terms.