Title: Characterisation of microstructure and its effect on the strength and toughness of 17-4PH stainless steel

Authors: C.R. Das, A.K. Bhaduri, S.K. Albert, A. Dasgupta

Addresses: Materials Technology Division, Indira Gandhi Centre for Atomic Research, Kalpakkam 603102, India. ' Materials Technology Division, Indira Gandhi Centre for Atomic Research, Kalpakkam 603102, India. ' Materials Technology Division, Indira Gandhi Centre for Atomic Research, Kalpakkam 603102, India. ' Physical Metallurgy Division, Indira Gandhi Centre for Atomic Research, Kalpakkam 603102, India

Abstract: The influence of microstructure on the strength and toughness of 17-4 Precipitation-Hardened (PH) Stainless Steel (SS) was studied as a function of duration of ageing at 783 K. Lath martensite is formed in this steel in its solution-annealed condition. X-ray diffraction studies detected the formation of a copper-rich phase after ageing for 0.25 h, with the amount of the copper-rich precipitates increasing with the duration of ageing. The coarsening of the copper-rich precipitates on ageing for 2 h led to a sharp decrease in hardness, which was attributable to the transformation of the coherent copper-rich body centred cubic (b.c.c.) phase to the incoherent copper rich face centred cubic (f.c.c.) phase. Further ageing for 4 h led to a dip in hardness and strength and an increase in toughness. The dip in hardness upon long-term ageing could be attributed to the formation of coarse copper-rich precipitates, which also led to an improvement in the toughness of the material.

Keywords: 17-4PH stainless steel; steel microstructure; strength; toughness; hardness; long-term ageing.

DOI: 10.1504/IJNEST.2009.028601

International Journal of Nuclear Energy Science and Technology, 2009 Vol.4 No.4, pp.355 - 365

Available online: 19 Sep 2009 *

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