INFLUENCE OF WARM ROLLING AND RECRYSTALLIZATION ANNEALING ON MECHANICAL AND METALLOGRAPHIC PROPERTIES OF THE SUPERALLOY N07080

Additional strengthening of superalloy N07080 described in this work was achieved by warm rolling. Control of the ratio of strength and ductile properties of the superalloy is possible by appropriate selection of the amount of warm deformation and the appropriate selection of the partial recrystallization temperature. In addition, recrystallization annealing makes it possible to equalize the grain size across the cross section of the warm rolled bars, which before recrystallization differ significantly in size in the central and peripheral parts of the bars.

WARM DEFORMATION BEHAVIOR OF A 65MN SPRING STEEL

The warm deformation behavior of 65Mn spring steel has been carried out by a thermomechanical simulator. The deformation temperatures are in the range of 550 ~ 700℃ and strain rates are in the range of 0.001 ~ 1 s-1. The deformation activation energy is calculated to be 486.829 KJ•mol-1. The strain compensated Arrhenius-type constitutive model was established. The relationship materials constants and strain were fitted with an 8th order polynomial. It was found that the strain has a significant influence on the instability map. At the strain is 0.3, the optimum flow zone may take place with the deformation temperatures higher than 626 ℃ and strain rate in the range of 0.001 ~ 1 s-1.

MECHANICAL BEHAVIOR AND MICROSTRUCTURE EVOLUTION OF THE Ti-3Al-5Mo-4.5V ALLOY AT AN ELEVATED DEFORMATION TEMPERATURE

A high-performance titanium alloy requires a fine and homogenous microstructure. The rational deformation process parameters of the Ti-3Al-5Mo-4.5V (TC16) titanium alloy can contribute to achieving this important microstructure. Hot-compression experiments were performed at temperatures in the range 100–800 °C and at strain rates of 0.1 s–1 to 10.0 s–1. The effects of deformation temperatures and deformation rates on the mechanical behaviour and microstructure evolution were analysed and discussed. The softening mechanism of the Ti-3Al-5Mo-4.5V alloy at an elevated deformation temperature was revealed. Experimental results showed that 500 °C is the critical deformation temperature to distinguish the warm-deformation region of 100–400 °C and the hot-deformation region of 500–800 °C. The softening mechanism is dominated by -phase spheroidization in the temperature range 100–400 °C with a higher strain rate of 10.0 s–1. The softening mechanism is dominated by a local temperature rise in the temperature range 500–800 °C with a lower strain rate of 0.1 s–1.

PRECIPITATION STATE OF WARM WORKED AA7050 ALLOY: EFFECT ON TOUGHNESS BEHAVIOR

Usually strength-toughness combination in aluminum alloys is improved by heat treatment (solid solution followed by quenching and reheating) after a deformation process at high temperature. In some cases a cold working step is added in the manufacturing process before heat treatment aimed to enhance the alloy strength. In recent time, some trials have been carried out finalized to replace the cold working step with a warm deformation. Such process route appeared to be quite effective in improving the toughness behavior of 7xxx alloys. Anyway e metallurgical explanation for such behavior has not still be reported . In this a comparison of the precipitation state following the two different routes is reported. Results show clear differences in the nanoprecipitation densities in the two cases, claiming for their responsibility in the definition of the toughness behavior.