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Effect of microstructure on the critical strain to onset of serrated flow in modified 9Cr–1Mo steel

2011; Elsevier BV; Volume: 89; Linguagem: Inglês

10.1016/j.ijpvp.2011.10.021

1879-3541

K.S. Chandravathi, K. Laha, P. Parameswaran, M.D. Mathew,

High Temperature Alloys and Creep

The influence of microstructure on the strain to onset of serrated flow in modified 9Cr–1Mo steel has been studied at 573 K. The different microstructures have been developed by soaking the steel at different temperatures starts at a temperature below Ac1 to temperature above Ac4 followed by oil quenching and tempering at 1033 K for 1 h. Soaking the steel in the intercritical temperature range (between Ac1 and Ac3) reduced the hardness and tensile strength of the steel whereas soaking at temperatures above Ac3 increased the hardness and tensile strength until the occurrence of relatively soft δ-ferrite for soaking at temperatures above Ac4. The δ-ferrite formation reduced the hardness of the steel. The steel showed serrated flow in the load-elongation curves at 573 K in all the microstructural conditions except for those having coarse prior austenite grain. The critical plastic strain to the onset of serrated flow was found to increase with hardness of the steel, as influenced by different microstructures. The variation of hardness, tensile strength and the critical plastic strain to onset of serration flow had been rationalized on the basis of the inter-barrier spacing to dislocation motion in the steel.