Effect of Structure Transformation on Transient Creep Behavior of AlAg System

Abstract

The transient creep of Al‐16 wt% Ag and Al‐16 wt% Ag‐0.1 wt% Zr solid solution alloys is investigated in the temperature range 428 to 673 K for various ageing times under constant load. The subsequent decrease and increase in the values of creep parameters n and β with increasing ageing times and ageing temperatures has been explained on the basis of structure transformations occuring in Al‐Ag alloys. It was found that the addition of Zr to Al‐16 wt% Ag alloy accelerates the precipitation of GP zones, γ′‐phase, and γ‐phase. TEM investigations confirmed the above effects. The mean values of the activation energy of both alloys were found to be equal to that quoted for dislocation intersection.

Study of precipitates formation in Al-4.5Wt%Cu and Al-4.5Wt%Cu-0.1Wt%In alloys using creep measurements and positron annihilation technique

“…These values of activation energy are consistent with that quoted for dislocation intersection. This is acceptable since dislocation intersection process is activated by energies ranging between 15 to 25 kJ/mol for Al alloys [20][21][22].…”

Effect of Cyclic Stress Reduction on the Creep Behaviour of Al-Ag and Al-Ag-Zr Alloys Containing γ′ and γ Precipitates

“…3, 4 and 5] is still fixed. The higher values of ε for alloy aged at 673 as compared with the corresponding values for alloy aged at 548 K may be due to existence of stable γ-plates which is known to be thick and of less volume fraction, the matrix thus gets clean and the motion of dislocation should be much easier (DEAF et al , 1998. Close examination of a number of TEM micrographs in both alloys, showed that the size of γ \ -phase in alloy B -with Zr addition-is coarser than that in alloy A (compare the precipitates size in Figs.…”

Transient and Steady State Creep of Al-10 wt% Ag and Al-22 wt% Ag Alloys Containing ??- and ?-Precipitates

“…4). These precipitates with higher density are usually more effective as dislocations locking agents [2,5,12,13,[20][21][22][23]. A higher Ag content in alloy B is assumed to accelerate the rate of dissolution of GP zones and the rate of formation and growth of g 0 -plates as will be discussed later.…”

“…Such a coarsening results in an increase in the precipitate thickness concurrently with a decrease in their number. So, the number of obstacles for the dislocation motion will extensively be reduced leading to loss of strength [5,12,20,21], i.e. increasing n, b and e st values.…”

“…1 (2001) fraction (see Fig. 7), they are considered to be less effective as impeding agents for dislocation motion [5,20,21].…”