Wettability and reactivity of ZrB2 substrates with liquid Al

Wetting characteristics of the Al/ZrB2 system were experimentally determined by the sessile drop method with application of separate heating of the ZrB2 and Al samples and combined with in situ cleaning of Al drop from native oxide film directly in vacuum chamber. The tests were performed in ultrahigh vacuum of 10−6 mbar at temperatures 710, 800, and 900 °C as well as in flowing inert gas (Ar) atmosphere at 1400 °C. The results evidenced that liquid Al does not wet ZrB2 substrate at 710 and 800 °C, forming high contact angles (θ) of 128° and 120°, respectively. At 900 °C, wetting phenomenon (θ < 90°) occurs in 29th minute and the contact angle decreases monotonically to the final value of 80°. At 1400 °C, wetting takes place immediately after drop deposition with a fast decrease in the contact angle to 76°. The solidified Al/ZrB2 couples were studied by scanning and transmission electron microscopy coupled with x-ray energy diffraction spectroscopy. Structural characterization revealed that only in the Al/ZrB2 couple produced at the highest temperature of 1400 °C new phases (Al3Zr, AlB2 and α-Al2O3) were formed

Cr cluster characterization in Cu-Cr-Zr alloy after ECAP processing and aging using SANS and HAADF-STEM

International audienceThe precipitation of nano-sized Cr clusters was investigated in a commercial Cu-1Cr-0.1Zr (wt.%) alloy processed by Equal-Channel Angular Pressing (ECAP) and subsequent aging at 550 °C for 4 hours using small angle neutron scattering (SANS) measurements and high-angle annular dark-field-scanning transmission electron microscopy (HAADF-STEM). The size and volume fraction of nano-sized Cr clusters were estimated using both techniques. These parameters assessed from SANS (d~3.2 nm, Fv~1.1 %) agreed reasonably with those from HAADF-STEM (d ~2.5 nm, Fv~2.3%). Besides nano-sized Cr clusters, HAADF-STEM technique evidenced the presence of rare cuboid and spheroid sub-micronic Cr particles about 380-620 nm mean size. Both techniques did not evidence the presence of intermetallic CuxZry phases within the aging conditions

On some Features of the Grain and Subgrain Size in a Cu-Cr-Zr Alloy After ECAP Processing and Aging

A Cu-1Cr-0.1Zr alloy has been subjected to ECAP processing via route Bc and aging at 250-800°C. Electron BackScatter diffraction (EBSD), Transmission Electron Microscopy (TEM) and X-Ray Diffraction Line Profile Analysis (XRDLPA) techniques have been used to unveil some peculiarities of the grain and subgrain structure with a special emphasis on the comparison of the grain size estimated by the three techniques. For the alloy ECAP processed and aged up to 16 passes, the grain size (from EBSD, 0.2 < d < 5 μm), subgrain size (from TEM, d ~ 0.75 μm) and “apparent” average crystallite size (from XRDLPA, d < 0.25 μm) are manifestly different. The results were compared to the published data and analyzed based on the fundamental aspects of these techniques

Characteristics of intermetallic phases in Cu/(Sn,Ni) diffusion couples annealed at 220 °C

The influence of Ni addition (5 at.%) on the morphology and chemical composition of the phases formedduring solid state reaction in Cu/(Sn,Ni) diffusion couples, annealed at 220 C for different periods oftime, was investigated. Chemical analysis of the reaction zone performed using scanning electron microscopy(SEM/EDS) identified several intermetallic phases. Near to the copper substrate, a thin andcontinuous layer of the Cu$_3$Sn phase was observed. Moving towards the (Sn,Ni) end of the diffusioncouple, the (Cu$_{1x}$Ni$_x$)$_6$Sn$_5$ phase was identified. This phase was represented by two types of structures: adiscontinuous layer located close to the Cu$_3$Sn phase, and precipitates (needles or faced) within the(Sn,Ni) end. These structures of (Cu$_{1x}$Ni$_x$)$_6$Sn$_5$ also varied in chemical composition. The experiment withsynchrotron radiation demonstrated two crystallographic variants of the Cu$_6$Sn$_5$ phase: hightemperaturehexagonal $\eta$ and low-temperature monoclinic $\eta'$; however, only the hexagonal variantwas confirmed by TEM. Differences in the morphology and chemical composition of the (Cu$_{1x}$Ni$_x$)$_6$Sn$_5$ phase were attributed to various mechanisms of their formation. The precipitates with a higher contentof Ni were most probably transformed from the Ni$_3$Sn$_4$ phase present in the initial (Ni,Sn) end-member,while the formation of the Ni-poor layer took place as a result of diffusion at the initial interface. Afterthe annealing experiment, the (Ni$_{1x}$Cu$_x$)$_3$Sn$_4$ phase was observed beyond the interface area as small, irregularly distributed precipitates in the (Sn,Ni) end-member. TEM examination allowed for the precisephase characterisation of the mentioned intermetallics. Moreover, except for the strong reflectionsvisible in SADP fitted to the hexagonal $\eta$-Cu$_6$Sn$_5$ phase, additional reflections were observed andassigned to the cubic Cu$_9$NiSn$_3$ phase

Morphology and chemical composition of Cu/Sn/Cu and Cu(5 at-%Ni)/Sn/Cu(5 at-%Ni) interconnections

In the present paper, scanning and transmission electron microscopies as well as energy dispersive X-ray spectroscopy investigations were performed to describe the morphology and chemical composition of the intermetallic phases growing in Cu/Sn/Cu and Cu(Ni)/Sn/Cu(Ni) interconnections during the diffusion soldering process. The obtained results revealed that even a small amount of Ni addition (5 at-%) to the Cu substrate totally changes the morphology and the rate of formation of the intermetallic phase layers in the solder/substrate reaction zone of the interconnections prepared at the same time and joining temperature conditions. The presented studies are promising in terms of the shortening of the soldering time in the elecronic industry