Melt-extraction Technique Research Articles

Production of rapid quenched copper-based solder using the melt-extraction technique

One of the ways to improve the properties of high-temperature solders consists in their achieving an amorphous or crystalline state by rapid quenching from the melted state. In order to produce wire and bars with a section up to 2 mm, the authors propose extraction of the melt. They propose a theoretical solution to the problem of solidification of the melt on the rotating crystallizer taking into account the principal technological characteristics of the process: the speed of rotation of the drum, the material of which it is made, the temperature of superheating of the melt, and the depth of immersion of the drum into the melt. The melt is permitted to arrive from the bottom and there is a laminar flow of the liquid along the surface of the crystallizer. The rapid quenching of high-temperature solders on the basis of the CuP and CuZn systems allows good quality wire to be produced with sufficient productivity with high plasticity to exchange the solders of silver in automatic ways of brazing, brazing of items with reduced dimensions and with thin walls, in brazing in ovens and in brazing with an r.f. current.

The influence of Nb addition on structure and properties of rapidly solidified intermetallics

The intermetallic alloys Ti-15wt.%Al-7wt.%Cu, Ti-15wt.%Al-7wt.%Cu-10wt.%Nb and Ti-15wt.% Al-14wt.%Cu were vacuum arc melted followed by rapid solidification by the pendant drop melt extraction technique in vacuum. A detailed characterization of these rapidly solidified materials was conducted using light optical microscopy, scanning electron microscopy-energy dispersive spectroscopy, microhardness, bend ductility tests, scanning transmission electron microscopy, X-ray diffraction and differential thermal analysis. The presence of niobium improved chemical homogeneity of the copper and alluminum and refined the microstructure, resulting in improved ductility at room temperature.

Crystallization of a rapidly solidified Al 2O 3-ZrO 2 eutectic glass

Glasses of the Al 2 O 3 -ZrO 2 eutectic composition were prepared by a melt extraction technique, and subjected to a variety of heat treatments. The first phase to crystallize from the glass was tetragonal ZrO 2 at 944 °C, followed by S-Al 2 O 3 above 1000 °C, α-Al 2 O 3 and m-ZrO 2 appeared at 1450 °C. The early crystalline phases exhibited enhanced mutual solid solubility. The δ-Al 2 O 3 phase contained up to 10.2 mol% ZrO 2 and the tetragonal ZrO 2 phase contained up to 14.1 mol% Al 2 O 3 for crystallite sizes ≤ 40 ran. As the crystallite size increased to a few 100 nm under heat treatment, equilibrium solute concentrations were attained. The largest tetragonal ZrO 2 particle observed was 0.3 μ m. There was no detectable difference between the Al 2 O 3 content in tetragonal and monoclinic particles of similar sizes. The apparent activation energy for growth of the tetragonal ZrO 2 in the temperature range of 950 °C to 1200 °C is found to be 10.8 × 10 4 J/mol.

Production of dental alloy by the melt extraction technique

Filaments of a commercial dental alloy (Ag3Sn) have been produced using the technique of pendant drop melt extraction. The filaments are 50 μm in diameter with a mean grain size of 5μm. Both the mechanical and structural properties of these wires have been determined to show that the results are consistent with those predicted in a previous study on small flakes made by the “gun” splat quenching technique. The ultimate tensile strength and ductility of these wires are significantly superior to samples made by chill block casting. Simple amalgamation experiments have been undertaken to confirm that alloys made in this way would be acceptable in practical situations.

A program for the calculation of X-ray reflection intensities, Part 2

The current work presents an exhaustively study on cooling rate-dependent yield behavior of Cu50Zr50 (at%) and Ni56Nb44metallic glass (MG) wires fabricated by a melt-extraction technique. After tension test, based on the measurement of the fracture angle, the yield behavior of the MG wires with different diameters is analyzed. Based on the Mohr-Columb criterion, the cohesion strength of the MG wires is evaluated. According to the free volume model, the cohesion strength of the MG wires is quantitatively predicted. The correlation between the yield behavior and the quantity of free volume in the glassy phase is elucidated.