On the γ′ precipitates of the normal and inverse Portevin-Le Châtelier effect in a wrought Ni-base superalloy

doi:10.1016/j.jmst.2018.09.014

Abstract

Abstract:

The Portevin-Le Chatelier (PLC) effects in a wrought Ni-base superalloy with different γ? precipitates contents have been investigated. Detailed analysis on the serration type of the tensile curves indicates that the γ? precipitates have a decisive influence on the transformation from normal to inverse PLC behavior, which is rarely proposed in other works. It is considered that the γ? precipitates play the same role in PLC effect as temperature and strain rate for the investigated wrought Ni-base superalloy.

Key words: Normal and inverse PLC effect, γ? precipitates;, Dynamic strain aging, Critical strain, Wrought Ni-base superalloy

Xinguang Wang, Guoming Han, Chuanyong Cui, Shuai Guan, Jinguo Li, Guichen Hou, Yizhou Zhou, Xiaofeng Sun. On the γ′ precipitates of the normal and inverse Portevin-Le Châtelier effect in a wrought Ni-base superalloy[J]. J. Mater. Sci. Technol., 2019, 35(1): 84-87.

Figures/Tables 5

Fig. 1. Microstructures of Nimonic 263 alloy aged at 800?°C for: (a) 0.15?h, (b) 2?h, (c) 25?h, (d) 50?h, (e) 300?h, (f) 500?h.

Fig. 2. True stress?strain curves (a) and a portion for the onset of PLC effect is magnified in (b) and (c) of Nimonic 263 alloy with different aging time after tensile tests at 500?°C with a constant strain rate of 4?×?10-4?s-1. Inset in (a) showing the PLC types of serrations observed. For a better view, the curves are deliberately shifted along the ordinate axis.

Table 1 Variation of the mean radius (r?(t), nm) and the mean edge-to-edge inter-precipitate distance (L?(t), nm) of the γ? precipitates with the aging time.

Aging time (h)														2	10			25		50	100	300	500
$r ? (t)$	6		10		14		21		27		40		48
$L ? (t)$		15		25		35		48		73		105				140

Table 1 Variation of the mean radius (r?(t), nm) and the mean edge-to-edge inter-precipitate distance (L?(t), nm) of the γ? precipitates with the aging time.

Aging time (h)														2	10			25		50	100	300	500
$r ? (t)$	6		10		14		21		27		40		48
$L ? (t)$		15		25		35		48		73		105				140

Fig. 3. Dependence of PLC effect on the γ? phase: (a) Aging time vs critical strain; (b) Mean radius of γ? phase vs critical strain; (c) Mean edge-to-edge interprecipitate distance vs critical strain.

Table 2 Variation of serration type at various testing conditions with different γ? contents, which summarized from Ref. [21].

Conditions		0% γ?	15% γ?	30% γ?
3?×?10^-3?s^-1	500?°C	A?+?B	A?+?B	B
	550?°C	-	-	B?+?C
	600?°C	B	B	B?+?C
3?×?10^-4?s^-1	500?°C	B	B	C
	550?°C	B?+?C	C	C
	600?°C	C	C	-
1?×?10^-4?s^-1	500?°C	B	B	C
	550?°C	B?+?C	C	C
	600?°C	C	C	Smooth

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