Correlation between microstructure and corrosion behaviour of Bi-Zn solder alloys

Abstract

Bi-Zn solder alloys with different Zn contents (1.5, 2.7 and 5wt-%) were prepared by casting and the correlation between the microstructure and corrosion behaviour by mean of direct current electrochemical tests was studied. The surface analysis of the hypoeutectic Bi-Zn alloy samples revealed the presence of needle-like ZnO and very small agglomerated spherical particles. By contrast, eutectic alloy presented the formation of a uniform and compact film of ZnO, which is related to the better distribution of Zinc in the Bi-rich matrix. Despite the increase in Zn content compared to the hypoeutectic alloy, the corrosion rate showed similar values regardless of its content in the alloy. The Bi-5wt-% Zn alloy presented the highest limiting current density, and consequently, the highest degree of corrosion of the studied alloys. The pro-eutectic phase consisting of large and thick Zn fibres is preferentially dissolved, promoting a selective attack that penetrates inside the sample.

Microstructure Growth Morphologies, Macrosegregation, and Microhardness in Bi–Sb Thermal Interface Alloys

“…[53][54][55][56][57][58] Despite many studies having found equations given by λ 2 ¼ constant (V ) À2/3 for different alloy systems, [59][60][61][62] the effects of lateral solute segregation on the wavelengths of instabilities along the sides of primary dendritic stems for Bi-based alloys are still not well understood. Herein, a single power law in which the exponent À1.1 characterizes the experimental evolution of λ 2 as a function of V L for all Bi- (5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20) wt% Sb alloys is proposed. Figure 10 shows Vickers microhardness (HV) for the analyzed Bi-Sb alloys as a function of Sb concentration along the length of DS castings, highlighting the solidification microstructure morphologies.…”

“…irregular shape ! trigonal pattern) to be identified in Bi- (5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20) wt% Sb alloys as the solute content increases. 2) Although a general power-type experimental law given by λ 1 ¼ constant (Ṫ) À0.…”

“…[12] As a matter of fact, Bi-based alloys are also suggested for various applications as thermoelectric materials, [13][14][15] optical and electro-optical devices, [16] hall sensors, [17] and lubricant materials. [18] However, the great challenge in developing new Bi alloys is the enhancement of a specific property without compromising other important physical properties, as stated by Septimio et al [19] From this perspective, controlling the microstructure through solidification thermal parameters is of critical importance because it plays an important role on the resulting properties of metallic alloys. Therefore, an in-depth understanding of how solidification parameters affect the microstructural evolution is vital to provide key information for the design of Bi alloys suitable for applications such as TIMs.…”

“…Despite Bi-based alloys having exhibited promising potential as TIMs in microelectronics cooling applications, understanding the microstructure evolution of these alloys and the consequent effects on the resulting properties still remains an essential task to be accomplished. Herein, a directional solidification technique is used to investigate microstructural features and Vickers microhardness of Bi (5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20) wt% Sb alloys with a focus on the roles of alloy composition, solidification thermal parameters, and macrosegregation. The results show the formation of aligned Bi-rich dendrites in a broad range of cooling rates from about 0.2 to 25 C s À1 .…”

Nephelium lappaceum Extract as an Organic Inhibitor to Control the Corrosion of Carbon Steel Weldment in the Acidic Environment

“…In HCl solution, the corrosion rate of WM is the highest because of the largest grain size and the lowest hardness. Low hardness metals are known to have low corrosion resistance [29][30][31]. In addition, the formed precipitates during the welding process contribute to the highest corrosion rate in the WM zone [32].…”