Metallurgical Quality Assessment of Modified Zn–Al–Cu Alloys

Abstract

Zinc casting alloys are characterised by good technological and mechanical properties. The main problems connected with zinc casting alloying technology is creation of a coarse-grained, dendritic structure in the slowly solidifying castings. As a result of occurrence of dendritic micro segregation effects and structural instability the differentiation of properties can be observed. For the quality improvement of the liquid metal, which after casting in mould will assure the configuration of the required casting structure and guarantee good and stable properties, the modification operations are used. In the paper the influence of the chemical modification of Zn–Al–Cu casting alloys on the chosen properties (corrosion resistance, wear resistance, hardness) and the structure of zinc casting alloys have been researched. The results of the assessment of the alloy, both: in the in-state and after the modification state have been analysed with the application of quality assessment methods, particularly the statistical tools. The usage of control charts of variables reflecting the measurable properties of the Zn–Al–Cu–Sr and Zn–Al–Cu–Ti–B alloys have made the complex assessment possible. The modified alloys have been produced by the adding the modified Sr and Ti–B in the range between 0,1 and 1 % to the aluminium master alloy and casting to the metal casting dies.