A. Dziadoń

Properties of Mg laser alloyed with Al or AlSi20

The alloyed surface layers were produced using thin Al or AlSi20 plates, which were first diffusion bonded and then melted into the Mg substrate. The microscopic analysis showed that alloying with Al led to the formation of an Al-enriched surface layer containing a high volume fraction of an Mg17Al12 phase. Applying AlSi20, on the other hand, resulted in the formation of an Al/Si-enriched layer containing Mg2Si, Mg2Al3 and Mg17Al12 phases. The experimental results indicate that surface alloying of Mg with Al or AlSi20 using the presented method improved the properties of the material. The microhardness of the Al- and Al/Si-enriched layers was much higher than that of the substrate. Higher wear resistance was observed for the Al/Si-enriched layer. The alloyed layers provided a certain level of protection of Mg against corrosion. The specimens alloyed with Al showed better anticorrosive properties than those alloyed with AlSi20.

Surface Cracking of Laser Melted Ti-6Al-4V Alloy

Surface Cracking of Laser Melted Ti-6Al-4V Alloy The characteristic features of surface cracking observed after laser melting with CO2 and Nd:YAG laser were described. The cracks were always present, their length approaching some part of melted zone and scarcely dependent on laser melting conditions. The appearance of cracks was attributed mainly to martensitic transformation within the surface layer. The possible contribution of developed thermal stresses cannot be also excluded. The existence of cracks may be utilized for the enhancement of bone - implant strength.

Effects of the pouring temperature on the formation of the bonding zone between AZ91 and AlSi17 in the compound casting process

The compound casting process was used to join AZ91 magnesium alloy to AlSi17 aluminium alloy. Liquid AZ91 was poured onto a solid AlSi17 insert placed in a steel mould heated to 370 °C. The experimental results showed that the temperature of the AZ91 melt affected the formation of the bonding zone between the two alloys. A continuous bonding zone was formed by applying a pouring temperature of 650 °C. The use of higher temperatures, i.e. 680 °C and 700 °C, did not lead to the formation of a continuous metallurgical transition zone at the AZ91/AlSi17 interface. The bonding zone was analysed using an optical microscope and a scanning electron microscope equipped with an energy dispersive X-ray (EDS) detector. The structural constituents of the bonding zone near the AlSi17 alloy were: an Al3Mg2 intermetallic phase, primary Si particles surrounded by a rim of an Mg2Si intermetallic phase and fine Mg2Si particles. The area of the bonding zone that was adjacent to the AZ91 alloy had a eutectic structure composed of an Mg17Al12 intermetallic phase and a solid solution of Al and Si in Mg.