Dose rate effect on micro-structure and hardness of Hastelloy-N irradiated by Xe ions

Figures & data

Table 1. Chemical composition of the Hastelloy-N alloy.

Element	Ni	Mo	Cr	Fe	Mn	Si	C
wt%	71.17	16.1	7.39	3.87	0.43	0.029	0.04
Element	N	Ti	Cu	Co	P	S	B
wt%	0.002	<0.002	<0.002	<0.002	<0.002	<0.002	<0.002

Figure 1. Metallography of Hastelloy-N alloy: (a) before heat treatment and (b) after heat treatment.

Table 2. Irradiation conditions at the Institute of Modern Physics.

		Dose rate	Irradiation	Beam current	Irradiation
Alloy	Ions	(dpa/s)	dose (dpa)	(ions/cm^2 s)	temperature (K)	Vacuum (Pa)
Ni-based	7 MeV Xe^+	3.0×10^−4	0.5, 1, 2, 4, 6, 8	7.1×10^10	300	1.2×10^−5
	2 MeV Xe^+	1.3×10^−3	0.5, 1, 2, 4	7.8×10^10		1.4×10^−5

Figure 2. Damage rate and Xe deposition with Xe⁺ implantation depth calculated by SRIM: black line represents the damage rate for high dose rate (1.3×10⁻³ dpa/s) and red line represents the damage rate for low dose rate (3.0×10⁻⁴ dpa/s).

Figure 3. Hardness versus indentation depth for Hastelloy-N alloy.

Figure 4. TEM micrograph of Hastelloy-N alloy: (a) before implantation and (b) irradiation with 7 MeV Xe⁺ at 0.5 dpa.

Figure 5. Hardness of alloy as a function of irradiation dose at different dose rates.

Figure 6. S-parameter as a function of depth in the alloys irradiated with different dose.

Table 3. Number density and mean size of defects at the different irradiation conditions.

	Implantation		Mean	Number
	energy	Dose	size	density
Specimens	(Xe^+)	(dpa)	(nm)	(10^11 cm^−2)
Hastelloy-N alloy	7 MeV	0.5	–	–
		1	3	3.3
		2	5	2.7
		4	8	2.3
		6	17	1.8
		8	24	1.6
	2 MeV	0.5	1	5.4
		1	2	3.0
		2	3	2.6
		4	6	2.1

Note: “–” no visible irradiation defects are observed.

Figure 7. TEM micrograph of Hastelloy-N alloy irradiated by different Xe ion doses with a low dose rate. (a) Magnified image of region A of Figure 4(b).

Figure 8. TEM micrograph of Hastelloy-N alloy irradiated by different Xe ion doses with a high dose rate.

Figure 9. Hardness of alloy (irradiation with 7 MeV Xe⁺) as a function of the average S-parameter (in depth from 50 nm to 150 nm).

Figure 10. Hardness as a function of average obstacle spacing.