Effect of iodine partial pressure on the iodine stress corrosion cracking behaviors of Zr–Sn–Nb alloy using the ring tensile test

In order to evaluate the effect of iodine partial pressure on the iodine stress corrosion cracking (I-SCC) behaviors of a Zr–Sn–Nb alloy, ring tensile tests were conducted at 350 °C and in atmosphere without iodine and with iodine partial pressure of 10², 10³, and 10⁴ Pa, respectively. Results show that the maximum load, fracture displacement, tensile strength, and fracture energy of the Zr–Sn–Nb specimens decrease monotonically with the increase of iodine partial pressure. The fracture morphology of specimen with 10² Pa iodine exhibits two different fracture regions. One is the mixture form of ductile and brittle fracture, and the other is only ductile fracture. For the specimen with 10³ Pa, stair-shaped fracture surface is formed as a result of the alternative propagation of transgranular cracks and intergranular cracks. The critical iodine partial pressure of the Zr–Sn–Nb alloys is lower than 10² Pa under the present conditions.