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This paper describes the hydrogen embrittlement (HE) o f an A1-Li alloy aged a t 190°C and with d i f f e r e n t durations o f ageing (10, 15, 20 and 30 hr). Two techniques were employed t o measure HE : a) cathodic polarization i n a molten salts bath with-3 VIAg on tensile specimens ; b) gaseous hydrogenation on disks. Hydrogen charging was achieved a t 190°C. The results show that HE i s important when the a1 1 oy i s i n the over-aged condition.

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The behavior of a Type 316 L austenitic stainless steel subject to creep and cyclic tension under imposed load is examined at room temperature. Tests are carried out on the material in both the annealed and work-hardened state; in the latter case the influence of an initial hardening by cyclic tension on the subsequent creep behavior, together with the influence of creep hardening on the subsequent cyclic tension behavior, are determined. All tests are conducted with stresses from half the 0.2 percent yield stress up to a stress leading to an initial plastic strain of about 10 percent. We demonstrate the existence of a (critical) stress limit for creep and a stress limit for (cyclic) accommodation. The creep strain, for a given time interval, increases with the applied stress and, in general, the material continues to creep after 10 000 h. The plastic elongation, between the 1st and the 1000th cycle, that occurs during cyclic tension tests on the annealed materials goes through a maximum when plotted as a function of the maximum applied stress. The creep strain obtained after prior cyclic tension (1000 cycles at the same maximum stress level) has the same stress dependence as the plastic strain that occurs between the 1st and the 1000th cycle, and exhibits a maximum. A creep pre-strain before the cyclic tension tests considerably decreases the elongation measured during cycling.