Effect Of Lead Addition Research Articles

Effect of Lead Addition and Milling on Densification and Mechanical Properties of 6061 Aluminium Alloys

In the present work, one batch of prealloyed 6061Al powder was mixed with different lead compositions (5, 10, 15 vol.%) and another set with same composition was ball-milled for 5 h at 300 rpm. Microstructural features such as lattice constant, crystallite size, particle size and morphology were studied using XRD, particle size analyzer and SEM. Both the as-mixed as well as ball-milled powders were compacted at 300 MPa and sintered under N2 atmosphere for 1 h in tube furnace at 590 °C. The ball milling of 6061Al alloy powder improved sinter density and densification while lead addition showed negligible influence on these parameters. The microstructure of as-mixed 6061Al–Pb alloys exhibited equiaxial morphology whereas ball-milling resulted in elongated grains with uniform lead distribution. Quasi-static compressive mechanical behavior was investigated for 6061Al–Pb alloys at 1 × 10−3 s−1 strain rate. Results indicated that ultimate compressive and yield strength were sensitive to milling and lead volume fraction.

Effects of lead addition on the microstructure and mechanical properties of as-cast Mg–4Zn alloys

Abstract The effects of 1.0 and 3.0 wt% lead (Pb) additions on the microstructure and mechanical properties of as-cast Mg–4 wt%Zn alloys were studied. Tensile and nanoindentation tests were conducted to evaluate the mechanical properties of the as-cast alloys and the nanomechanical properties of primary α-Mg phase, respectively. Significant improvements of mechanical properties were achieved including the ultimate tensile strength (UTS) from 213 MPa to 225 MPa and elongation (E) from 14% to 20% by adding only 1.0 wt% Pb into the Mg–4Zn alloy. It was found that the additions of Pb change the morphology of intermetallic phases in cast Mg–4%Zn alloy. In addition, Pb suppressed the formation of the intermetallic compounds and slightly decreased the grain size of Mg–4%Zn alloy. The nanohardness of primary α-Mg increases steady with addition of Pb.

The activation of sphalerite by lead — a flotation perspective

The activation of sphalerite by some metal salts has been briefly reviewed and the influence of lead nitrate on sphalerite in the presence of potassium ethyl xanthate has been investigated by a combination of batch flotation tests and solution analyses on pulps containing a mixture of sphalerite and quartz. The effect of lead addition, of pH and of complexant on the flotation behaviour has led to the conclusion that in mildly acidic conditions the activating entity is lead ion whereas in mildly alkaline conditions the activating entity is lead hydroxide. Some comparisons between lead activated sphalerite and galena have been made. The consequences of these findings in the separation of galena from sphalerite in practical flotation have been briefly discussed.

Transmission Electron Microscopy of Pb-doped Bi2Sr2Ca2Cu30x /Ag composite conductors prepared by the two-powder process: The effect of lead addition on critical current and microstructure

Recent studies indicate that a more uniform and more fully reacted Pb-doped Bi2Sr2Ca2Cu3Ox (Bi-2223)phase can be reproducibly obtained within silver sheaths using a two-powder precursor in which the formation of Bi-2223 primarily involves reaction between lead-doped Bi2Sr2CaCu2Oz (Bi-2212) and other non-superconducting phases. In particular, the specific method of introducing lead was reported to significantly influence the phase evolution and superconducting properties of Bi-2223/Ag composite conductors.2 Composites made from lead-doped Bi-2212, where lead is fully incorporated into the Bi-2212 phase prior to its conversion to Bi-2223, exhibit sharper transition temperatures and higher critical current densities than those where lead is added in the form of non-superconducting PbO or Ca2PbO4 phases (Fig. I).2 In this paper, we present a combined investigation by transmission electron microscopy(TEM) and energy dispersive x-ray spectroscopy (EDX) of the composition and microstructure of the (Bi-2223)/Ag composite conductors. The observed differences are discussed with respect to the measured electrical properties.

Thermodynamic study of the effects of Pb-addition on the formation of the 2223 phase in the Bi-based superconductor system

Abstract Bi2Sr2Ca2Cu3Oy, Bi3Sr2Ca2Cu3Oy and Bi2PbSr2Ca2Cu3Oy were prepared by conventional solid-state reaction method. Based on the results of thermogravimetry, inductively coupled plasma emission spectroscopy, and power X-ray diffraction, the thermo-dynamic factors were discussed qualitatively for the effect of lead addition on the formation of the 2223 phase during reaction. Partial substitution of bismuth by lead is favorable to the development of the 2223 phase, but the 2223 phase is thermodynamically less stable than the 2212 phase. Compared with the case of the unleaded samples, when lead is added the contents of lead and bismuth in the bulk are greatly reduced during sintering. The partial evaporation of lead and bismuth increases the entropy change of the system, which may induce the enhancement of the formation of the 2223 phase.

The effect of lead addition to the Bi Cu HTSC: Phase separation

Abstract We have prepared a series of samples with nominal composition Bi 2−x Pb x Sr 2 Ca 2 Cu 3 O y , 0 ≤ x ≤ 2. By means of X-ray diffraction and scanning electron microscopy we have observed that for low Pb/Bi ratios lead incorporates into the structure of the so called 80 K and 110 K Bi-superconductors, which normally coexist. However the 110 K superconducting phase becomes predominant as the sintering time increases. From x=0.5 upwards an almost Bi-free second phase appears. It is non-superconducting and its structure appears to be hexagonal. Some Ca 2 PbO 4 is also present for x > 0.5.

The Effect of Lead on the Machining of Low Carbon Steel with TiN Coated Tools

Summary The effect of lead addition on the machining of a 0.15%C steel has been investigated by estimating the temperature distribution in TiN coated and tin coated M42 high speed steel tools. TiN coating reduced the contact length by 40% when cutting the leaded steel but only slightly in the case of the equivalent non-leaded steel. Consequently the maximum rake face temperature was reduced by more than 150°C for the former but only 75°C for the latter. The TiN coated M42 tools cut the leaded steel at speeds up to 300 m/min whereas the uncoated tools failed within 10s at 230 m/min; in the case of the non-leaded steel catastrophic failure occurred at 170 m/min with both coated and uncoated tools. Lead reduced the total shear strain in both primary and secondary shear zones and made manganese sulphide more effective in promoting free-cutting behaviour. The effect of lead in reducing temperature caused the built-up edge (BUE) to persist to 75 m/min; TiN coating was removed from HSS and cemented carbide tools within the BUE speed range.

Effect of dispersity on the catalytic function of the metal in nickel-containing catalysts

On the basis of X-ray analysis data the effect of dispersity and habit of the nickel crystallite, as well as the effect of lead addition on the catalytic properties of nickel-containing zeolites of Y-type, is studied. As model reactions, the disproportionation of toluene and the methanation of carbon monoxide are used. The observed changes in the catalytic activity of differently dispersed nickel are related to the changes in the ratio between the crystallographic faces, determining the catalytic functions of the metal. A specific influence of the zeolite carrier on the dispersity is established.

Machining Characteristics of Leaded Steel

The effects of lead addition in alloy steel upon the metal-cutting process were explored over a wide range of conditions. In particular, a range of cutting speeds (from 50 to 800 fpm) and workpiece hardness (from 230 to 450 Bhn) were investigated on one work-piece material (4340) using principally a carbide (C-6) cutting tool. Orthogonal (two-dimensional) data was taken to describe the metal-cutting process, and tool-life data were obtained by running a typical production tool to failure at the various cutting conditions. Several mechanisms to explain experimental results, including lead acting as a lubricant, are discussed.