Abhishek Pandey

Changes in the properties of Cu-Al-Mn shape memory alloy due to quaternary addition of different elements

Advantages of Cu based shape memory alloy include amongst other features, high transformation temperature, low cost of production, ease in manufacturing processes and ability to vary the achieved properties through alloying additions. It has been often reported that these alloys are very sensitive to the alloying additions in terms of properties achieved and phase precipitation necessary for development of shape memory properties. This behaviour in Cu based shape memory alloys i.e. being very sensitive to its constituents can be used positively to design alloys with pre set properties if the alloying additions and their percentages are properly controlled. In an attempt to understand the effect of different alloying additions, 2% of different elements [Zn, Si, Mg & Cr] were added to a known Cu-based shape memory alloy [Cu-12.5 wt% of Al-5 wt % of Mn]. The objective was to ascertain changes or improvements achieved due to the additions in terms of microstructural changes, hardness, phase precipitation and transformation temperatures. Attempts have been made to analyze the changes in properties achieved in the base Cu-Al-Mn alloys due to the quaternary additions. Grain structure with α+β phases, which is a pre requisite for martensite formation on quenching is seen in all the alloys indicating that all the alloys have potential to exhibit the shape memory behaviour. The martensite formation with different morphologies is observed in the quenched samples however. XRD results have identified the precipitated phases to be the martensitic phases. The DSC results indicate clear transformation peaks in most of the samples with significantly high transformation temperatures. The findings confirm the variation in properties achieved due to different additions and improvements achieved in terms of higher transformation temperatures and martensite formation due to the alloying additions. An attempt has been made to understand the findings.

Effect of Varying Al/Mn Ratio on Phase Transformation in Cu-Al-Mn Shape Memory Alloys

In the present study, an attempt has been made to study the effect of the proportion of the main alloying constituents in a Cu–Al–Mn alloy, which is a known shape memory material. Four compositions of the alloy with varying ratios of Al:Mn, varying from 1 to 4 [added to copper], were synthesized using the liquid metallurgy route. After appropriate heat treatment to induce shape memory behaviour, they were studied for microstructure, X-ray diffraction, hardness and transformation temperature in an attempt to understand the effect of the varying ratios of the major alloying constituents on the properties mentioned. With an increase in the Al:Mn ratio, increase in grain size as well as cast hardness were observed. On the other hand, an increase in percentage decrease in hardness was observed with increase in Al:Mn ratio. Increase in Al:Mn ratio also favoured formation of martensitic structure with less amount of retained austenite.

Effect of Alloying Additions on the Properties Affecting Shape Memory Properties of Cu–12.5Al–5Mn Alloy

The paper discusses the attempt made to understand the role of different alloying additions (Fe, Ni, Cr and Ti) to a Cu–12.5Al–5Mn alloy known to exhibit shape memory behaviour on its microstructure, phase precipitation and effect on transition temperatures after optimising the heat treatment cycles to precipitate the required martensite phase. The effect of the additions has been studied on the optimising conditions, phases precipitated through microstructural analysis‚ X-ray diffraction and transformation temperatures through Differential Scanning Calorimetric studies. In this study, the samples were prepared through liquid metallurgy route by melting pure metals. The cast alloys were subject to homogenisation treatment at 200 °C for 2 h in a muffle furnace and furnace cooled. In an attempt to precipitate the maximum amount of the desired microstructure of martensite in the quenched samples, the quenching cycle was optimised for each alloy by holding them for different duration of time from 30 to 120 min at 920 °C followed by ice quenching. X-ray diffraction studies carried out on the quenched samples indicate martensitic phase precipitation; however, in some cases, the precipitation is incomplete. Differential Scanning Calorimetric (DSC) studies carried out on quenched samples indicate clear transformation peaks in all the samples which are significantly higher than conventionally reported. The range of phase retention was used to determine the enthalpy and entropy changes. The findings confirm the possibility of changing the shape memory properties such as martensite formation, transitions temperatures, retention times, thermal properties as in entropy and enthalpy change with changing alloying constituents. Attempts have been made to study the shape memory properties of selected alloys that have exhibited promising improvement over the base alloy. The study can help pinpoint compositions with the desired properties in such alloy systems.

Effect of Nano CeO2 Addition on the Microstructure and Properties of a Cu-Al-Ni Shape Memory Alloy

This article deals with the effect of adding nano CeO2 to act as a grain pinner/refiner to a known Cu-Al-Ni shape memory alloy. Elements were taken in a predefined ratio to prepare 300 g alloy per batch and melted in an induction furnace. Casting was followed by homogenization at 1173 K (900 °C) and rolling to make sheets of 0.5-mm thickness. Further, samples were characterized for microstructure using optical and electron microscope, hardness, and different phase studies by X-ray and transformation temperatures by differential scanning calorimetry. X-ray peak broadenings and changes were investigated to estimate the crystallite size, lattice strain, and phase changes due to different processing steps. A nearly uniform distribution of CeO2 and better martensitic structure were observed with increasing CeO2. The addition of CeO2 also shows a visible effect on the transformation temperature and phase formation.

Study of effect of Fe, Cr and Ti on the martensite phase formation in Cu-12.5wt%Al-5wt%Mn SMA

Copper based shape memory alloys are studied throughout the world for their high transition temperatures and high thermal stability. Among Copper based shape memory alloys(SMAs), Cu-Al-Mn SMAs have shown good ductility and high transition temperature. Only those alloy systems that can show the formation of β phase are capable to demonstrate the shape memory properties. In this paper the effects of the alloying elements on the formation of martensite phase have been studied exclusively. Addition of 1 wt% of Fe, Cr and Ti to the Cu-12.5Al-5Mn shape memory alloy has been investigated in detail. Therefore, four alloys have been synthesized through liquid metallurgy route using pure metals of 99.9% purity in a melting furnace weighing 1kg each. Samples were heat treated at the temperature of 920 ̊C for 2 hours and then quenched in ice water. The optical micrographs show the formation of the martensite structures in all the samples except in the samples in which 1 wt% Fe was added. X-Ray diffractions also revealed the same facts as obtained in the optical microscopy. Vickers Hardness of all four samples were carried out. The result shows no sign of martensite formation in sample containing Fe; therefore, this alloy should not be used for further study in the direction of understanding shape memory behaviors of the copper based shape memory alloys. Moreover, it was also observed that the addition of Cr yielded good martensitic formation as compared to the alloy containing Ti. Copyright

Effects of Different Quaternary Additions in the Properties of a Cu-Al-Mn Shape Memory Alloy

In the present study, Cu-12.5u2009wt. %Al-5u2009wt. %Mn-80.5u2009wt. % shape memory alloy is chosen as the base alloy and 2u2009wt. % of quaternary additions of Fe, Ni, and Ti added to the base alloy. The effects of these additions on in terms of feasibility, microstructure, hardness, and transformation temperature were studied. The findings suggest the possibility to improve martensite formation, attain higher transitions temperatures, and longer retention over the base alloy through such additions.