The morphology of precipitates in an AlGe Alloy—I. experimental observations

Influence of Cu additions on the morphology of GeSi precipitates in an Al-Ge-Si alloy

“…Similar inter-A MAJOR feature of the precipitation processes in pretations were also provided to explain changes in the binary Al-Ge and Al-Si alloys is the wide variety of shapes morphology of the Ge precipitates in an Al-1.3 wt pct Ge and habit planes of Ge and Si precipitates. [1,2,3] This is the alloy, in the sequence of {111} Al triangular plates → ͗100͘ Al direct consequence of the dissimilarities in the crystal struclaths → {100} Al plates, as functions of aging temperatures tures and of the large differences in the atomic volumes of ranging from 150 ЊC to 250 ЊC. [2] These results are indicative the parent and product phases.…”

“…[2] Given these similarities tates on the quenched-in excess vacancies [10,11] and variations in local vacancy supersaturation. [1,9] between the ͗100͘ Al laths formed in binary Al-Ge [3] and ternary Al-Ge-Si alloys, [8][9][10][11] it shows that Si additions to Figure 2(b) represents a transmission electron micrograph obtained from the baseline alloy when aged at 160 ЊC for Al-Ge alloys do not alter the crystallographic nature (i.e., habit plane, orientation relationships with the Al matrix, 24 hours. The micrograph was imaged near the ͗100͘ Al zone axis and was taken from a region of the thin foil where the growth direction, etc.)…”

“…[1,2,9] In this context, clusters are stress free, thereby giving rise to the equiaxed shape of the resultant GeSi precipitates. Detailed TEM studit should be noted that the ͗100͘ Al laths of pure Ge precipitates, having the {001} Al habit plane, are also associated ies, however, revealed that the morphology of the precipitates varies from grain to grain as well locally within the with moiré fringes, [2,3] and that the appearance of such moiré fringes is understood to be due to good matching between grains. Such an observation is consistent with and attributed to the strong dependence of nucleation of the GeSi precipithe atomic spacing in the Al matrix and the ͗100͘ Al laths of Ge precipitates along the lath axis.…”

“…pct hand, the equiaxed morphology of the diamond cubic precipGe alloy, for example, it has been shown that variations itates is not observed in either of the binary systems. [1][2][3]7] in quench-bath temperatures and preaging times at room Furthermore, unlike those reported in the case of pure Ge temperature prior to final aging (in the temperature range and Si precipitates, [1] there has been no report of any definite of 200 ЊC to 300 ЊC) develop a variety of morphologies of pattern in the variation of morphology of the GeSi precipithe Ge precipitates. [7] This was attributed to the formation tates across the grain body due to changes in the local vacancy concentrations.…”

“…These observations are attributed to the variations in local vacancy supersaturation. [1,2,3] Using an Al-1.8 at. pct hand, the equiaxed morphology of the diamond cubic precipGe alloy, for example, it has been shown that variations itates is not observed in either of the binary systems.…”