Alloy annealing

Volter and Alsdorf (52) obtained a relation of a very similar character for the dependence of the catalytic activity in formic acid decomposition on the composition of the nickel-copper alloys. However, extending the times of the alloy annealing for their better homogenization caused the maxima on the catalytic activity curves to disappear. 

Curie temperature and lattice parameters of TiBe2 Cu alloys annealed at 850 ° C for 90 h (Giorgi et al. 1979). 

Fig. 6.9. Effect of heat treatment on hysteresis loops of a 65%Ni-35%Fe alloy, annealed at 1000 °C (a) rapidly cooled (b) slowly cooled (c) cooled in a longitudinal field and (d) cooled in a transverse field. (Adapted from Bozorth, 1951.)...

Large numbers of ordered structures can be formed by appropriate annealing conditions, and these structures play a large part in determining the physical, especially mechanical, properties of the alloys. Annealing is therefore a very important process in the production of materials with specific properties. 

Fig. 2. Effect of nickel content on fracture toughness and retained austenite of Fe-Ni-0.5 A1 alloys annealed at 550 C and tested at -196 C.

Fig. 6. Contributions of A1 and Cu to toughness and strength of Fe-12Ni alloy annealed at 450 C and tested at -196"C.

For some systems, even though they do not form bulk alloys, annealing can lead to the formation of so-called surface alloys, where mixing is confined to the first atomic layer [97Bes]. An example is Ag/Pt(lll), where annealing to T = 600 K leads to the formation of a real mixture where small Ag clusters are dissolved in the first Pt layer (0 < 0.5 ML) and vice versa (0.5 ML < 0 < 1 ML) [93R6d]. The fads values derived for tins system consequently do not correspond to the adsorption energy of Ag atoms on ideal Pt(l 11) terraces but presumably to desorption from a Ag-Pt adatom gas or from substitutional sites. 

ROC] X-ray diffraction, Mossbauer spectroscopy -y Fe4N + Cr, mechanical alloying, annealing at 190°C... 

Figure 15 shows the Vickers hardness test results for various alloys. The increase in the Ca content of the Pb-0.5 wt% Ag - Ca alloy was considered to increase the Vickers hardness of the alloy. The rolling rate increased the hardness of the Pb-0.5 wt% Ag - Ca alloy, but after annealing, the hardness decreased. Because the Vickers hardness shows a constant value after annealing at 200 C for 48 h, it was considered that the strain in the anode material could be removed by annealing at 200 C for 48 h. The Pb-0.5 wt% Ag - Ca alloy annealed at 200 C for 48 h after rolling showed the same or better mechanical properties relative to the conventional Pb-1.0 wt% Ag alloy. 

From arc-melted alloys annealed at 750 °C, landelli (1983) recorded the formation of DyCuSi with the ordered Nijln-type [superstructure of the AlB2-type, POj/mmc, a = 4.146(2), c = 7.416(4)]. The superstructure reflections were said to he very faint and with respect to the different results obtained by Rieger and Parth6 (1969a) from arc-melted alloys the new phase was suspected to be a low-temperature modification. For sample preparation and purities of starting materials, see LaCuSi. 

Raman (1968) investigated the phase equilibria within the concentration section ErAl Si, by means of X-ray powder analysis of as-cast alloys (arc melted) as well as of alloys, annealed for 3 d at 100 °C in evacuated silica tubes (air cooled). Starting materials were Er 99.9%, Al 99.99% and Si 99.99%. ErAlg25 10.75 was observed to crystallize with the CsCl-type of structure with space group Pm3m and a unit cell dimension of a = 3.388(5). The alloys ErAlgjSiy [a = 6.865(5), = 4.307(5), c —... 

Pecharsky (1979), from X-ray powder data of arc-melted alloys annealed at 800°C, observed the formation of a compound ErRc4Si2 with the ZrFe4Si2-type of structure P42/mnm, a = 7.301(5) and c = 4.103(2) for details of sample preparation, see Tb-Re-Si. 

LuCoSij crystallizes with the CeNiSij-type structure (Cmcm, a = 3.951, h — 16.067 and c = 3.915) Yarovets (1978) from X-ray powder data of arc-melted alloys annealed at 800 ° C for 720 h in evacuated silica tubes. 

---