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2 Zeszyty Naukowe. Mechanika / Politechnika Opolska

2 2010

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Structure and mechanical properties of Ni - 51.8 at % Ti shape memory alloy after thermomechanical cycling

100%

Blahož O. , Kursa M.

Zeszyty Naukowe. Mechanika / Politechnika Opolska

2010

tom z. 97

7-7

This article deals with an effect of a thermo-mechanical cycling on structural and mechanical characteristics of Ni - Ti alloys, especially on Ni - 51.8 at. % Ti. Applications in modern industry often exploit materials with special properties. Ones of these materials are alloys Ni - Ti with their shape memory effect based on phase transformations in structure of these materials. For successful use in practice it is very important to know if thermomechanical loading during utilisation of shape memory behaviour changing structural or mechanical properties. For verification of these effects were prepared samples which was cycled at various conditions and then observed by metallographic methods which informed us about homogeneity of the alloy and micro-structural changes within thermo-mechanical processes. Next part of experiment consisted measurement of microhardness and stress-strain tests on cycled and non-cycled samples to evaluate effect of cycling on mechanical properties and pseudoelasticity.

Structure characteristic of modify magnesium alloy MgAl8MnCa

61%

Cížek L. , Kedroň J. , Tylšar S. , Blahož O. , Prażmowski M. , Bański R.

Zeszyty Naukowe. Mechanika / Politechnika Opolska

2010

tom z. 97

13-14

Magnesium alloys has been used for a wide variety of applications, namely from the reason of their low density and high strength-to-weight ratio. Low inertia, which results from its low density, is advantageous in rapidly moving parts, for example automobile wheels and other automobile parts [1-2]. The basic magnesium alloys include ones which contain manganese, aluminium, zinc and other elements which allow obtaining suitable properties. Scope of utilisation of foundry magnesium alloys is continuously being extended, so if we want to operate as competitive producers, it is necessary to investigate very actively properties of individual alloys, optimise their chemical composition, study issues of their metallurgical preparation, verify experimentally their casting properties and conditions of successful casting of castings by individual methods, including heat treatment, forming and others specials methods of processing as are application of new forming method ECAP. Application of this method on aluminium alloys is described by many authors. From the reason low formability metals with hexagonal lattice the application of this method on magnesium alloys is now developed [3]. Paper presents results of investigations in new commercial prepared of modify magnesium alloy MgAl8MnCa with the following chemical composition (wt %): Al - 7,8; Zn - 0.05; Mn - 0.172; Ca - 0.9; rest Mg. Modify magnesium alloy MgAl8MnCa is a competitive cost alloys with aluminum 380. It is a creep resistant alloy with the capability of long-term operation at temperatures up to 150°C under high loads. This alloy exhibits good castability, corrosion resistance and mechanical properties at room temperature, similar or better to AZ91D. The main modifying element is Ca. Comparison the basic mechanical properties are shown in Table 1 [4]. The creep resistance of the alloy is substantially superior to that of commercial magnesium alloys at temperature of 130-150°C under stresses of 50-80MPa. The main applications targeted by this alloy include gearbox housings, valve covers, intake manifolds, oil pans, oil pumps and many under the hood components. For the metallographic analysis of structure magnesium alloy MgAl8MnCa the light microscopy and SEM were used.