The interdiffusion in liquid alloys of alkali metals with lead

The mutual diffusion in liquid cesium-lead alloys containing from 20 to 70 at.% Pb is investigated by a gamma-ray attenuation technique. The obtained data are compared with the results of similar studies for Li-Pb, Na-Pb, and K-Pb melts, carried out by us earlier. The concentration dependences of the interdiffusion coefficient for alkali-lead liquid systems demonstrate pronounced maxima in the vicinity of 20 or 50 at.% Pb. These phenomena confirm a tendency for chemical short-range ordering in liquid alloys.

A Proposal of Inelastic Constitutive Equations of Lead Alloys Used for Structural Tests Simulating Severe Accident Conditions

This paper studies inelastic stress-strain relationship equation and creep rupture equation and creep strain equation of 99%lead-1% antimony alloy. Under the severe accident conditions, structural materials of nuclear power plants are subjected to excessive high temperature. Although it is very essential to clarify how the structure collapses under the severe accident conditions, there’re no experimental evidences of failure modes and the failure mechanisms in such high temperatures are not clarified. However, it is very difficult and expensive to perform structural tests using actual structural materials, such as austenitic stainless steels. Therefore, the authors propose to use lead alloys instead of actual structural materials. Because the strength of such alloys is much poorer than that of the actual structural materials, failure can be observed at much low temperature and by much small load. For demonstration of analogy between the failure mechanisms of lead alloy structure at low temperature and those of the actual structures at extremely elevated temperature, numerical analyses are required. The authors proposes inelastic constitutive equations of lead alloy based on a series of material tests. Nonlinear numerical analyses, e.g. finite element analyses, can be performed using the proposed equations.

A Meso Level FE Model for the Impact Bullet - Yarn

This paper presents a study based on simulating the impact between a yarn (or a single fiber with greater dimensions) and a bullet, the impact velocity being 400 m/s. The characteristics of the involved materials are taken from literature. The yarn is considered isotrope, but the values of the characteristics are close to those of aramid fibers and cooper and lead alloys used for manufacturing the bullets. Analysing the yarn failure caused by a bullet, this FE model allows for identfying the stages in the failure process. First, the yarn is pushed by the bullet and the local elongation of the yarn is tacking place. The yarn rupture occurs in the �strangled� zones, caused by the stretch of the yarn directly supporting the impact. The breaking of the yarn in the thinned zone (more pronounced asymmetric breaking) and it is visible that the yarn elastic recoil starts next the bullet. The friction between the yarn and the bullet is only on the conical surface of the bullet in the tapered zone of the bullet. The yarn is detaching from the bullet (the contact zones between the bullet and the yarn in polymeric matrix become smaller, justifying a neglectable influence of the thermal effect). The yarn has no more contact with the bullet. This step is in the favor of the assumption that, in the actual multi-yarn impact, the other layers of yarns maintain the bullet and the first yarns in contact and this is why bunch of fibers (fragments of the failed yarns) are pressed against the bullet and remain on it. The simulation results were qualitatively validated by SEM investigations of fiber failure under the same conditions as the model.

LEAD AND LEAD ALLOYS FOAMS PRODUCTION

<span style="font-family: 'Times New Roman','serif'; font-size: 12pt; mso-fareast-font-family: 'Times New Roman'; mso-ansi-language: SK; mso-fareast-language: CS; mso-bidi-language: AR-SA;" lang="SK">Low-cost techniques for the manufacturing of lead and lead-alloys foams have been investigated in this work. In particular the “sintering and dissolution process” (SDP) and “replication process” (RP) have been focused and discussed. The effects of some production parameters have been investigated too: powder compacting pressure, composition of the base metal, granulometry, sintering time and temperature. Spherical urea and NaCl have been employed in the SDP method while in the replication process the viscosity of the melt has been found fundamental. Furthermore melt infiltration in the NaCl particulate has been found much easier if pressure is applied. Lead recovery and recycling of exhaust batteries into foam-based electrodes has been examined too with a novel method for the direct conversion of Pb scrap into lead foam.</span>

Comparisons of Soldering Alloys in Large Ceramic Substrate to Metal Heatsink Attachment Application

Tin-lead alloys have historically been popular in the electronics industry for use in solder-attach applications. Despite recent restrictions related to lead content, some industries continue to use lead based alloys in solder applications. Tin-lead based alloys, in particular, have proven to have excellent solderability to tin, nickel, copper, gold, and silver metallization surfaces. They have also performed better in reliability than most of the lead free solders. As a result of this, they are still widely used in the aerospace and military electronics industry. Hybrid microelectronics built for space applications use both Tin-Lead-Silver Alloy Sn62 and Lead Free Soldering Alloy Sn96; these solders are used both for wire and component attach as well as substrate to header attach. This article discusses the differences of these two solders, using both literature and experimental study. Experimental testing involving pull tests further supports this conclusion.