Composites of 2014 alloy made by dispersing 10 vol.% of fine (20–50 µm) SiC particles using vorte... more Composites of 2014 alloy made by dispersing 10 vol.% of fine (20–50 µm) SiC particles using vortex method ensuring uniform distribution of SiC particles in the matrix have shown uniform distribution of SiC particles. Mechanical properties of the composites have also registered an improvement over the alloy. In an attempt to further improve the properties, the composites were subjected to hot extrusion of cylindrical rods along with the alloys under similar experimental conditions. A temperature range of 300–350°C and an extrusion ratio of 10 : 1 were maintained during the process. The extruded samples were compared for their mechanical properties, and improvement was noted. The mechanism of material failure from fractographic studies showed difference in behaviour between the alloy and composite. Dry sliding wear studies carried out on extruded specimens exhibited improved wear behaviour in composites over alloys as measured by volume loss and wear rate. Wear mechanism was studied f...
Abstract The advantages of Cu-based shape memory alloys (SMAs) over the more popular Ni-Ti alloys... more Abstract The advantages of Cu-based shape memory alloys (SMAs) over the more popular Ni-Ti alloys are their low cost and easy processability coupled with good electrical and thermal conductivity. However, these alloys suffer from severe brittleness due to highly ordered structure causing difficulty in cold working; consequently, their applicability in the form of wires and sheets is impeded. In an attempt to improve the ductility of these alloys, varying amounts of Nb and Ag were added to Cu-12Al-4Mn, a known SMA, and the effect of these additives on the shape memory properties as well as the microstructure through grain refinement were analyzed. Detailed microstructural observations indicated that the addition of more than 2 wt% of Ag or Nb was detrimental to the martensitic structure that was formed on quenching. Furthermore, the addition of Nb led to the formation of a more desirable martensitic microstructure, namely the fine β1’ phase, whereas the inclusion of Ag caused the formation of the coarse γ′1 phase. Based on the observed strength and shape memory effect, it was concluded that Nb significantly improved the mechanical as well as the shape memory properties of the base alloy.
ABSTRACT Advantages of Cu based shape memory alloy include amongst other features, high transform... more ABSTRACT 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.
Composites of 2014 alloy made by dispersing 10 vol.% of fine (20–50 µm) SiC particles using vorte... more Composites of 2014 alloy made by dispersing 10 vol.% of fine (20–50 µm) SiC particles using vortex method ensuring uniform distribution of SiC particles in the matrix have shown uniform distribution of SiC particles. Mechanical properties of the composites have also registered an improvement over the alloy. In an attempt to further improve the properties, the composites were subjected to hot extrusion of cylindrical rods along with the alloys under similar experimental conditions. A temperature range of 300–350°C and an extrusion ratio of 10 : 1 were maintained during the process. The extruded samples were compared for their mechanical properties, and improvement was noted. The mechanism of material failure from fractographic studies showed difference in behaviour between the alloy and composite. Dry sliding wear studies carried out on extruded specimens exhibited improved wear behaviour in composites over alloys as measured by volume loss and wear rate. Wear mechanism was studied f...
Abstract The advantages of Cu-based shape memory alloys (SMAs) over the more popular Ni-Ti alloys... more Abstract The advantages of Cu-based shape memory alloys (SMAs) over the more popular Ni-Ti alloys are their low cost and easy processability coupled with good electrical and thermal conductivity. However, these alloys suffer from severe brittleness due to highly ordered structure causing difficulty in cold working; consequently, their applicability in the form of wires and sheets is impeded. In an attempt to improve the ductility of these alloys, varying amounts of Nb and Ag were added to Cu-12Al-4Mn, a known SMA, and the effect of these additives on the shape memory properties as well as the microstructure through grain refinement were analyzed. Detailed microstructural observations indicated that the addition of more than 2 wt% of Ag or Nb was detrimental to the martensitic structure that was formed on quenching. Furthermore, the addition of Nb led to the formation of a more desirable martensitic microstructure, namely the fine β1’ phase, whereas the inclusion of Ag caused the formation of the coarse γ′1 phase. Based on the observed strength and shape memory effect, it was concluded that Nb significantly improved the mechanical as well as the shape memory properties of the base alloy.
ABSTRACT Advantages of Cu based shape memory alloy include amongst other features, high transform... more ABSTRACT 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.
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Papers by Rupa Dasgupta