On the Aging and Precipitation of Al-Ag and Al-Zn Alloys

Polycrystalline specimens of Al-30wt % Ag and Al-30wt % Zn alloys, which were quenched into water from the temperature of solution heat treatment, were annealed at L.T. aging temperatures or reversion temperatures so as to make them contain zones of nearly equal radii for each alloy and various concentrations of solute element in zones. These specimens were cold rolled exactly to 50%, and then annealed at L. T. aging temperatures for varying time. The state of zones and precipitates were investigated by X-ray small-angle scattering photographs. The results obtained were as follows: (1) The precipitation ofγ'-phase began earlier in the specimens of Al-Ag alloy annealed at L. T. aging temperature before cold rolling than in those specimens annealed at reversion temperatures before cold rolling when annealed at L. T. aging temperatures after cold rolling. (2) The rate of precipitation of Zn solid solution in Al-Zn alloy did not depend upon the annealing temperature before cold rolling when cold rolled specimens were annealed at L. T. aging temperature. (3) In Al-Ag alloy, the rate of disappearance of G. P. zones at L. T. aging temperature depends mainly upon the annealing temperature before cold rolling. On the other hand, in Al-Zn alloy, the rate of disappearance of G. P. zones at L. T. aging temperature does not depened upon the annealing temperature before cold rolling. (4) These results may be explained without contradiction considering the relation of structures between matrix and precipitates and the deformation stacking faults

Fluctuation of the Solute Concentration in Al Rich Al-Zn Alloys

Several Al-Zn alloys containing 0.041-4.4 at % Zn were studied by means of measurements of electrical resistivity. The results obtained are as follows : (1) The electrical resistivity increases when the specimen is annealed at temperatures higher than the solvus temperature of the G.P. zones. The increase of the resistivity is due to the formation of fluctuation. (2) The electrical resistivity of the specimen containing fluctuation is dependent upon annealing temperature only and independent of quenching temperature. (3) The fluctuation is formed in very dilute alloys as 0.041 at % Zn at temperatures higher than the solvus temperature of the G.P. zones. (4) The formation energy of vacancy and the migration energy of the Zn atom in the alloys determined by the formation process of fluctuation are in good agreement with those by the formation process of G.P. zones. (5) In spite of the result (4), it seems that the fluctuation is not the same as the small G.P. zones which are observed in the early stage of aging

Deformation and Prefered Orientation of Precipitates in Cold Worked Al-Zn Alloys

Fiber textures of drawn wires of Al-Zn alloys containing precipitates were studied mainly by X-ray methods. In supersaturated solid solution the wire texture was a double fiber texture with [100]and [111]. It was considered that a phase precipitates were rotated with matrix, while they were deformed. And then the matrix containing stable precipitates (Zn) had [100] and [111] textures. The intense spots, corresponding to [111] fiber texture of matrix, in the Debye rings of (002)p and (101)p planes of precipitates were clearly observed. But, on the other hand, spots, corresponding to [100] fiber texture of matrix, shown the prefered orientation of precipitates in (002)p Debye ring were very weak and brodening

G.P.zones and Clusters in Al-Zn Alloy and Al-Cu Alloy

As to Al-Zn alloy, the difference between the formation of G.P.zones and that of clusters was investigated by measurements of electrical resistivity. The results obtained were summarised as follows: (1) G.P.zones formed during the quench and quenched-in vacancies increase greatly as-quenched resistivity P(o) as quenching temperature Tq is raised, and clusters increase slightly P(o) as Tq is lowered. (2) For one Tq and one Ta, the time required to reach P(e)' for Al-1.3at % Zn alloy is longer than that for Al-3.0at % Zn alloy. This is due to the difference of number of zinc atom in the clusters. (3) For one Ta and one concentration of zinc, the time required to reach p'(e) at Tq = 170℃ is longer than that at Tq = 300℃. This is due to the difference in concentration of quenchedin vacancies. As to Al-Cu alloy, the solvus temperature for G.P.zones was determined from the existence of P(m) in ageing curves by measurements of electrical resistivity. Consequently the solvus temperature is between 20℃ and 60℃

Grouth of G.P. zones in Al-Zn alloy

Metastable values of electrical resistivity, P(E)' obtained during isothermal ageing differs in each experimental run even when the conditions of quenching and ageing were carefully kept constant. This phenomenon is considered to result from the competitive growth of G.P.zones. The range of the values of P(E) under the same conditions of heat treatments were examined, and the results obtained are as follows: (1) Metastable values of resistivity, P(E), during ageing at 70℃ after quenching from 300℃ were in rather narrow range. On the other hand, the width of the range obtained during ageing at 50℃ was wide. (2) When the specimens were aged at first at 70℃ until the maximum values of resistivity, P(M), being reached and then aged at 50℃ for long time, the metastable values of resistivity, PE*, were obtained. And the width of discrepancy of values of P(E)* was nearly equal to that of P(E) which was obtained in the case of isothermal ageing at 70℃ after quenching from 300℃. (3) It may be concluded that the width of discrepancy of values of P(E)* becomes smaller since the width of discrepancy of the number of G.P.zones for all experiments which can grow through competitive growth is made small by 70℃ ageing than that immediately after quenching from 300℃

On the Apparent Activation Energy for Clustering in Dilute Al-Zn Alloys

The clustering phenomenon was observed when dilute Al-Zn alloys were annealed at temperatures higher than the solvus of the G.P.zones. In this report the apparent activation energy for clustering is estimated and compared with the experimental results. The estimated value of the apparent activation energy for clustering in several Al-Zn alloys comes to 0.51 eV, which is larger than the effective migration energy 0.43 eV of Zn atoms in Al-Zn alloys

Binding Energies between a Vacancy and a Cadmium, Indium or Tin Atom in Al-10wt % Zn, Al-3.0wt % Ag and Al-3.0wt % Cu Alloys

The changes of electrical resistivity of several alloys, that is, Al-10wt % Zn, Al-10wt % Zn-0.01wt % Cd, Al-10wt % Zn-0.01wt % In, Al-10wt % Zn-0.01wt % Sn, Al-3.0wt % Ag, Al-3.0wt % Ag-0.01wt % Cd, Al-3.0wt % Ag-0.01wt % In, Al3.0wt % Ag-0.0lwt % Sn, Al-3.0wt % Cu, Al-3.0wt % Cu-0.0lwt % Cd and Al-3.0wt % Cu-0.01wt % In, during isothermal aging after quenching were measured. The interactions between a vacancy and a cadmium, indium or tin atom in Al-10wt % Zn, Al-3.0wt % Ag and Al-3.0wt % Cu alloys were estimated. Binding energies obtained for Al-Zn, Al-Ag and Al-Cu base ternary alloys agree within experimental accuracy with each other

SAXS Intensity Measurements by Photographic Methods

Photographic method for measurement of small-angl X-ray scattering (SAXS) is improved. Intense pointfocussing incident beam is obtained by using doubly bent crystal monochromator made of aluminium single crystal. Microphotometry and the subsequent calculation to obtain profiles, Guinier and Porod radii, integrated intensities, and so on are facilitated by using microcomputer. Integrated SAXS intensities measured from an Al-Zn alloy which has been treated under the same heat treatment conditions are coincident with one another with probable errors less than ±6 % . Ratio of the integrated intensities obtained from two Al-Zn alloys of different composition is reasonable compared with the quasi-equilibrium phase diagram

SAXS from the GP Zones in Al-4mass % Cu Alloy at Initial Stages of Ageing

A series of small-angle X-ray scattering photographs with monochromated and point focussed copper Ka(1) radiation was taken of a single crystal of an Al-4mass % Cu alloy at the as-quenched state from 823K and at successive stages of ageing at 313K. The crystal was so oriented that the incident direction of the radiation was along [001] axis, and was cooled with liquid nitrogen during the exposure. The pattern of the as-quenched state was homogeneous, but each of the patterns of the aged states consisted of streaks along [100] and [010] directions and a quasi-ring around the trace of the incident beam on the film (even at the shortest ageing time. l6sec). The most intense regions were found in [100], [010] , [100] and [010] directions on the ring. With the progress of the ageing the streaks and the ring became more intense and narrower. The results can be interpreted from points of view of the formation of the GP zones parallel to {100} planes ab initio, the effect of the inter-particle interference on scattering of X-rays, and the growth of the GP zones with the ageing. Guinier radius of the GP zones at each stage can be obtained from intensity change along [110], and the values are reasonably consistent with those obtained from the cross section of the streak. The presence of multi-layer zones, besides the one-layer ones, is suggested from the humps found on several intensity curves along [100] at later stages

Binding Energies between a Vacancy and an Atom of Lead or Gold in Al-10wt % Zn Alloys

Binding energies between a vacancy and an atom of lead or gold were measured with the same method as those previously reported. The solid solubility of lead or gold in aluminium is very small, and the small quantity of precipitates are found along grain boundaries in this experiment. Therefore, it was not possible to determine the value of binding energy, but the lower limit of binding energy was estimated. The values of lower limit for Pb-Vacancy and Au-Vacancy binding energy were 0.38 eV and 0.35 eV, respectively