Next to their composition the properties are mainly improved by their microstructure. The finer the microstructure the better / higher the properties (Hall-Petch-relation). In general PLM alloys exhibit a micro-crystalline or in some cases even a nano-crystalline microstructure. Due to this fact strength properties and ductility are improved at the same time. For further improvements PLM is going to generate quasi-crystalline sections within nano-crystalline structures Accordingly, “up-to-date” development programs are conducted in cooperation with German and European industrial partners and Universities.
Aluminum already has a low density (2,7 – 2,9 g/cm3) compared to other metals like iron, nickel, titanium or steel. However, densities can be reduced even more by adding light weight elements such like silicon (Si), magnesium (Mg) and lithium (Li) or compounds of these elements such like Mg2Si. These low densities in combination with other improved properties (strength, fatigue) offer the best options for weight reduction – sometimes even without any design changes. The densities of PLM’s alloys are only 1/3 or only 1/6 of the densities of steel, KOVAR, INVAR or WCu, respectively. Due to this the purchasing volume (weight) is reduced for the customer drastically, however, producing the same number of components. This is an enormous cost advantage for all.
By alloying with specific elements (low solubility and low diffusivity in Al matrix) and by activating special strengthening mechanisms (dispersion strengthening, particle hardening) as well as by generating special microstructures (micro-, nano- or quasi-crystalline) excellent microstructure stabilities and by that improved properties are realized for application at elevated temperatures. PLM alloys are specially designed for applications in engine construction (pistons, intake valves, valve cap retainers), power generation (turbocharger wheels, components in jet engines) and nuclear power plants (energy moderation of thermal neutrons).
Thermal and electric conductivity are comparable to average values of conventional Al alloys. These conductivities in combination with other properties like strength at elevated service temperatures or a low coefficient of thermal expansion (CTE) make these alloys to ideal candidates for applications in opto-electronic devices (heat spreaders, heat sinks, metallic mirrors, guide bars and many others.
Young's Modulus of some of these alloys is in excess of 80 - 100 GPa thus exhibiting properties well above those values of conventional Al alloys. Some of the binary AlSi-alloys exhibit a Modulus of 120 GPa (AlSi70). Based on these values additional weight savings may become possible when components are re-designed (secondary weight savings).
By adding increasing amounts of Si to Al the coefficient of linear thermal expansion is reduced in a controlled manner thus realizing values between 24 ppm/K for pure Al and 7 ppm/K for AlSi70 (PLM-470). The combination of low density and low CTE makes these alloys an ideal and attractive replacement of Titanium, Kovar, Invar, WCu or MoCu. Furthermore, thermal conductivity of these binary AlSi alloys is superior compared to that one of the traditional alloys. These alloys also show no texture. This type of alloys can be used for application in optical and opto-electronic systems with significant advantages.
Wear resistance without any additional Coating is a new property for aluminum alloys. This is realized for AlSi alloys with some additional alloying elements such like transition metals (Fe, Ni, Cr, etc.) or refractory elements (Zr, Ti, Mo, V etc.). These additional elements strengthened the matrix itself thus giving good conditions for the sliding partner. For improving the wear resistance in addition the Si primary particles should have a size less than 10 µm. Furthermore, their shape should be rounded to avoid abrasive wear on the sliding counterparts during service.
Recycling of PLM's alloys is easily done. By filtration and degassing of the melt the highest quality can be guaranteed. Many alloys contain more expensive alloying elements. Therefore, recycling significantly contributes to well-balanced metal costs. At the same time PLM takes advantage of the lower energy costs for processing of secondary aluminum compared to the consumption of primary aluminum.