Analysis of the Microstructural Evolution during the Transient Upward, Downward and Horizontal Directional Solidification of the Al-1.2wt%Pb Monotectic Alloy

Monotectic alloys are of great industrial importance because of their favorable tribological behavior. Many studies in order to better understand the morphologies obtained by monotectic reaction have been developed. To better understand the morphologies obtained by monotectic Al-1.2wt%Pb alloy reaction, especially in relation to induced convective flow, this paper aims to compare the microstructural evolution of the alloy obteind by directional solidification in transient heat-flow conditions in upward, downwand and horizontal solidification devices. It was observed a morphology transition from particles to fibers on upward and downward cases and a morphology of only particles on the horizontal case. The classical relationship used for eutectic growth, λ2v = C, which was considered applicable to monotectic reactions, didn’t seemed to be valid in the interphase spacing evolution for the downward device, however power functions (λ = C.va) were found in all cases.

Thermodynamic modeling of the Al-K system

A thermodynamic modeling for the Al-K system is conducted. The thermodynamic parameters for liquid, (Al), and (K) are evaluated by using the experimental phase diagram data from the literature. The gas phase is described with an ideal gas model. The calculated Al-K phase diagram agrees well with the experimental data. In particular, the observed monotectic reaction is well described by the present calculation.

Formation of a Crystalline-Glass Composite in a Cu-Based Bulk Metallic Glass by Using the Cu-Pb Monotectic System

To synthesize a crystalline-glass composite in a Cu-based bulk metallic glass, the monotectic reaction was used. The (Zr-Sn-Pb)-rich crystalline phase was found to coexist with the (Cu-Ti-Ni)-rich glassy phase during the process of quenching from the melt in the (Cu47Ti33Zr11Ni6Sn2Si1)100-x+Pbx=1,2 system. Microstructures consisting of uniformly dispersed crystalline particles in the amorphous matrix were observed by scanning electron microscope (SEM) and transmission electron microscope (TEM). Compressive tests demonstrated that the fracture strain of the sample with a Pb content of 1 at% was three times higher than that of the sample with no Pb.

A Problem of Maya Metallurgy in the Medium Grijalva, Central Guatemala, and the Yucatan Peninsula: Copper-Lead Alloy

ABSTRACTThe study of 4 metallic artifacts from the Medium Grijalva, two bells, a bipointed awl, and a needle, and one bell from Huehuetenango, Guatemala, were studied using of elemental analysis by flame atomic absorption spectroscopy (FAAS), metallographic examination and typological classification. Several problems arose, including the need to have a clearer definition of bell types, better knowledge of the technology of production of needles and awls, and problems with the Cu-Pb alloys, especially if a how high a lead content forms a Cu-Pb alloy solution.Early analyses made of bells and copper artifacts from the Maya area, Western Mexico and Southwest USA shows variable but important amounts of lead. The Cu-Pb phase diagram shows a monotectic reaction where the metals have poorcapability of alloying or mixing, forming a eutectic at very low lead concentrations. Few metalographic studies of these alloys are reported in papers about historic metals. However, some ternary Cu-Pb alloys are found in recent literature. Does the low arsenic content as in the analysis of the Cu-PbMayan bells influence the properties of the alloys? The importance of the distribution of types of bells made of Cu-Pb could clarify possible cultural connections and trade among the Maya area, western Mexico and southwest United States. The possible introduction of metallurgy from and trade with South America makes this search of even more importance.