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Purpose This paper aims to discuss the effect of surface treatment on the wettability between copper and a lead-free solder paste. The industrial applications of laser technologies are increasing constantly. A specific laser treatment can modify the surface energy of copper and affect the wetting properties. Design/methodology/approach The surfaces of copper plates were treated using an Nd:YAG laser with varying laser powers. After laser surface treatment, wetting experiments were performed between the copper plates and SAC305 lead-free solder paste. The effect of laser treatment on copper surface was analysed using optical microscopy and scanning electron microscopy (SEM). Findings The experimental results showed that the wetting contact angles changed with the variation in laser power. Furthermore, it means that the surface energy of copper plates was changed by the laser treatment. The results demonstrated that the contact angles also changed when a different soldering paste was used. Originality/value Previous laser surface treatment can be a possible way to optimize the wettability between solders and substrates and to increase the quality of the soldered joints.

A new classification of different laser beam induced surface engineering technologies is offered in this paper. An in situ laser melt injection technology is applied in this paper to modify the surface of an inexpensive carbon steel substrate. Relatively large WCzTi particles were blown into a laser melt steel pool, and the desired (Ti,W)C carbide particles were precipitated upon cooling and solidification. Although these primary (Ti,W)C carbide particles were micrometre sized, additional nanosized (Fe,W) 6 C particles were found to precipitate during the subsequent heat treatment from an oversaturated steel matrix. Thus, a steel matrix surface nanocomposite was produced by the combination of in situ laser melt injection technology and subsequent heat treatment.

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The aim of the present work is to investigate the microstructure of Al-Pb monotectic surface layers generated by a laser surface alloying technique on the surface of an Al-4Cu-1.5Si-0.5Mg alloy. Monotectic alloys are generally used as materials for sliding bearings. Layers of a monotectic alloy generated by laser surface alloying have a potential for superior properties, because the rapid solidification during this process results in fine precipitation structures which can act as solid lubricant. The structure of the Al-Pb monotectic surface layers was observed in the light microscope and the scanning electron microscope. Volume fraction and size distribution of lead particles were determined by quantitative image analysis. Pin-on-disc experiments were carried out to characterize and compare the tribological properties of the Al-Pb monotecitc layers and cast Al-Cu-Si-Mg alloys.

For the general calculation of the transformation of steels the transformation diagram for isothermal transformation must be known. It is described, how from dilatometric measurements with continuous cooling the transformation at a constant temperature can be calculated. To do this, the simplex method must be used as iteration process to achieve sufficient precision. Even when measuring data are scattered around an ideal value by ± 5% the transformation diagram for isothermal transformation can be calculated with considerable accuracy. Berechnung des ZTU-Schaubildes fur isothermische Umwandlung aus Dilatometer-Messungen mit kontinuierlicher Abkuhlung. Fur die allgemeine Berechnung des Umwandlungsverhaltens von Stahlen ist die Kenntnis des ZTU-Schaubildes fur isothermische Umwandlung erforderlich. Es wird -zunachst fur ein Gefuqe -eine M6glichkeit gezeigt, aus Dilatometer-Messungen mit kontinuierlicher Abkuhlunq das Umwandlungsverhalten bei isothermischer Temperatur-Zeit-FOhrung zu berechnen. HierfOr muB als Iterationsverfahren die Simplex-Methode eingesetzt werden, um ausreichende Genauigkeiten zu erzielen. Auch bei einer Streuung der MeBwerte von ±5% urn einen idealen Wert kann das ZTU-Schaubild fiir isothermische Umwandlung mit guter Genauigkeit berechnet werden.

In the present study the analysis of 5 different mechanisms of porosity formation during laser melt injection (LMI) technology were performed. Experiments were supported by thermodynamic and fluid-flow analysis. Special attention should be paid to i. clean the surface of the substrate, ii. use inert shielding gas, iii. use proper particle size and gas velocity, iv. use proper laser power and laser beam velocity to control bath temperature and v. deoxidize the surface of the added particles.