Yielding Phenomenon of an Al-3% Li Alloy

Abstract

The effect of annealing on stress-strain curves of an Al-3% Li alloy which had been overaged and then cold-rolled was studied, by comparing with the changes in lattice constant and electrical resistivity and also in the transmission electron micrographs. A sharp yield drop followed by the propagation of Luders bands was observed when the Al-3% Li alloy wasThe above results were discussed in terms of general requirements for the yielding.It was concluded that the decomposition of the precipitates, AlLi, was not always necessary for the occurrence of the sharp yielding but promoted the pinning of dislocation sources near the boundaries.

Aging Characteristics of Rapidly Solidified Al-20 wt% Zn Alloy

“…8, might be due to zone formation [29] and the increased Bragg scattering as the clusters grow in size. Such rise in the electrical resistivity was previously attributed [30] to the dissolution of the b-phase which produced an increase of Zn atoms in the matrix. The room temperature resistivity values of Fig.…”

The role of lithium atoms in the structural changes in Al−Li alloy

“…Accordingly, the present observed recovery processes in the temperature range 25--450 ~ might be ascribed to the growth of coherent Guinier-Preston zones formed at relatively lower temperatures [9] and the precipitation of the ~-phase (Al-Li) in the temperature range 200--300 ~ [1]. Since no precipitate except (Al-Li) exists, the dissolution of ~-phase takes place in the temperature range 300--450 ~ [1]. The redissolution of this precipitatc caused ah increase in the Li concentration existing within the matrix, leading to an increase in electric resistivity of 3.3 #~cm (see Fig.…”

“…Above 450 ~ the loss in Li concentration in the matrix seems to be responsible for the observed increase in lattice parameter and decrease in electric resistivity. Duc to the existence of interaction energy between Li atoms and dislocations [1,3], stabilization of dislocations takes place asa process of anneal hardening [11], which leads to the observed increase in hardness above 450 ~…”

“…I t has been reported [1] t h a t in supersaturated Al-Li alloys, the fl-phase (Al-Li) preeipitated b y annealing in the t e m p e r a t u r e range of 150--300 oC and dissolved at higher t e m p e r a t u r e s leads to the dispersion of the exeess Li atoms b y diffusion t h r o u g h the matrix. Sueh struetural ehanges affeeted largely b o t h the eleetrieal [2] and meehanieal [1] properties of the alloy.…”

“…Sueh struetural ehanges affeeted largely b o t h the eleetrieal [2] and meehanieal [1] properties of the alloy.…”