**5. Brief applicability of Cu-based SMAs**

Predominantly, the shape memory applications can be separated into four classes as per the essential capacity of their memory component [106–109] where the SME can be utilized to create movement as well as load, and the SE can store the twisting vitality [110, 111]. The extraordinary conduct of SMAs has produced new applications in the aviation, automobile, robotization, and control, machine, vitality, synthetic handling, warming and ventilation, security and safety, and hardware (MEMS gadgets) ventures. A part of these applications applies comparative strategies, ideas or systems, which are additionally relevant for different regions. Most of these plausible applications are secured with the economically accessible parallel Nitinol SMA, where its operational temperature run lies around inside the standard scope of ecological temperature boundaries to which a traveler vehicle might be uncovered amid administration, for example, between −40°C to approx. +125°C [112, 113]. The binary alloy system of NiTi SMA with change temperatures from −50°C to approximately to +110°C [106] performs well for various cycles inside vehicle areas in varies range of performing temperatures [113, 114], however not in areas with higher temperatures, for example, under the motor hood. The SMAs ought to have a martensite finish temperature well over the most extreme working temperatures (see the dark spotted lines in **Figure 20**) so as to work appropriately. The correlation of the change temperature scopes of the most widely recognized SMAs that the less expensive Cu-Al-Ni SMAs can play out the change with temperatures up to 200°C, however, these SMAs are fragile, unsteady, have low exhaustion quality and are not appropriate for numerous cyclic activities [106, 113, 115–119]. A wide determination of high temperature SMAs are accessible, however, these materials are known as costly for automobile applications [113].

Since the 1980s, SMAs have been used in many different robotic systems, especially as micro-actuators or artificial muscles [123–125] as described by Furuya and Shimada [126] and Sreekumar et al. [127]. Today, most of the SMA robotic applications were biologically inspired (i.e., biomechanics) and widely utilized in biomedical areas but are also used extensively in other fields as well. The difficulties are to expand the execution and scaling down of the equipment stage and to build the insight of the coordinated framework (for example small-sizes, consistent and self-controlling). A few specialized issues were featured and should be settled, for example, clamping difficulties, miniature electrical connection (for micro robots), small strain, control issues and very low efficiency. Besides, part of these issues

**45**

robots DOF.

**Figure 20.**

**6. Summary**

and reduced the shocked waves of earthquake.

*commercially available and developed SMAs [106, 113, 120–122].*

*Cu-Based Shape Memory Alloys: Modified Structures and Their Related Properties*

has been controlled by choosing an appropriated modeling strategy as sensor to control and feedback. For instance, the control of resistance feedback is perfect for small scale robots as it takes out the additional requirement for extra sensors, in spite of the fact that the obtained limited accuracy [127]. Earlier, it was found that the response of the SMA actuator is mainly relying on structural design and thus limited the robotic functionalities in terms of the degree of freedom (DOF). On the other hands, the heating resistivity is a common technique been implemented for a micro-size SMA actuators, however, macro-size actuators are required to a direct heating source to acquire the shape memory features. In addition to enhance the frequency of the actuators, a capacitor will be attached for a faster heating response along with above-mentioned cooling methods that resulted in larger device shape [127]. Another problem to be mentioned that the complexity of the control system that found due to the large numbers of actuator were employed to increase the

*Operating temperature range for automobiles applications and the transformation temperatures for selected* 

Another significant implementation for shape memory as absorbers in bridges that been effectively used [128, 129]. According to the study was carried out by European Union on the earthquake damages and the way of finding a sustainable technology to prevent the disaster damage via seismic vibration. A research was conducted for as modeling for four story building, which was constructed using the tendons techniques to minimize the earthquake possible damage, where it was found that the building without SMA was completely destroyed while the incorporated building with SMA got less damage, whereby, the implemented tendons were used to absorb energy based on the shape memory feature of super-elastic behavior

In this chapter the characteristic of shape memory alloys in terms of microstructure, mechanical properties and thermal cyclic stress-strain curves of Cu-Al-Ni SMAs. The main benefits of these alloys can be obtained after the modifications were made, as, for a certain application, the selective of shape memory alloys

*DOI: http://dx.doi.org/10.5772/intechopen.86193*

*Cu-Based Shape Memory Alloys: Modified Structures and Their Related Properties DOI: http://dx.doi.org/10.5772/intechopen.86193*

#### **Figure 20.**

*Recent Advancements in the Metallurgical Engineering and Electrodeposition*

**5. Brief applicability of Cu-based SMAs**

costly for automobile applications [113].

restricted the grain growth by the pinning effect. Also, other elements have shown a significant effect on the mechanical properties of Cu-Al-Ni SMAs during the addition. For example, the rupture strain of Nb and V has increased up to 14 and 6%, respectively, which is much higher than the base alloy as reported by Gomes et al. [104]. The strain recovery by the shape memory effect (εSME) of the Cu-Al-Ni SMAs with and without the Ti additions was studies by Saud et al. [21], as shown in **Figure 18**. The results were shown that the addition of Ti with different mass percentages exhibited an increase in the values of strain recovery by the SME. These enhancements in references the strain recovery were attributed to the existence of the X-phase that was brought about by the Ti additions in the parent phase. Another study by the same authors [60] shown the effect of different percentage of 0.5, 1.0, and 1.5 wt.% of Sn addition on the stress–strain curves under multi-cycles of loading and unloading. It was found that the largest number of cycles was indicated with the Cu-Al-Ni-1 wt.%Sn SMA before the occurrence of fracture, as shown in **Figure 19(a–d)**. This improvement is due to two reasons: low porosity density and the finest particle size among the alloys.

Predominantly, the shape memory applications can be separated into four classes as per the essential capacity of their memory component [106–109] where the SME can be utilized to create movement as well as load, and the SE can store the twisting vitality [110, 111]. The extraordinary conduct of SMAs has produced new applications in the aviation, automobile, robotization, and control, machine, vitality, synthetic handling, warming and ventilation, security and safety, and hardware (MEMS gadgets) ventures. A part of these applications applies comparative strategies, ideas or systems, which are additionally relevant for different regions. Most of these plausible applications are secured with the economically accessible parallel Nitinol SMA, where its operational temperature run lies around inside the standard scope of ecological temperature boundaries to which a traveler vehicle might be uncovered amid administration, for example, between −40°C to approx. +125°C [112, 113]. The binary alloy system of NiTi SMA with change temperatures from −50°C to approximately to +110°C [106] performs well for various cycles inside vehicle areas in varies range of performing temperatures [113, 114], however not in areas with higher temperatures, for example, under the motor hood. The SMAs ought to have a martensite finish temperature well over the most extreme working temperatures (see the dark spotted lines in **Figure 20**) so as to work appropriately. The correlation of the change temperature scopes of the most widely recognized SMAs that the less expensive Cu-Al-Ni SMAs can play out the change with temperatures up to 200°C, however, these SMAs are fragile, unsteady, have low exhaustion quality and are not appropriate for numerous cyclic activities [106, 113, 115–119]. A wide determination of high temperature SMAs are accessible, however, these materials are known as

Since the 1980s, SMAs have been used in many different robotic systems, especially as micro-actuators or artificial muscles [123–125] as described by Furuya and Shimada [126] and Sreekumar et al. [127]. Today, most of the SMA robotic applications were biologically inspired (i.e., biomechanics) and widely utilized in biomedical areas but are also used extensively in other fields as well. The difficulties are to expand the execution and scaling down of the equipment stage and to build the insight of the coordinated framework (for example small-sizes, consistent and self-controlling). A few specialized issues were featured and should be settled, for example, clamping difficulties, miniature electrical connection (for micro robots), small strain, control issues and very low efficiency. Besides, part of these issues

**44**

*Operating temperature range for automobiles applications and the transformation temperatures for selected commercially available and developed SMAs [106, 113, 120–122].*

has been controlled by choosing an appropriated modeling strategy as sensor to control and feedback. For instance, the control of resistance feedback is perfect for small scale robots as it takes out the additional requirement for extra sensors, in spite of the fact that the obtained limited accuracy [127]. Earlier, it was found that the response of the SMA actuator is mainly relying on structural design and thus limited the robotic functionalities in terms of the degree of freedom (DOF). On the other hands, the heating resistivity is a common technique been implemented for a micro-size SMA actuators, however, macro-size actuators are required to a direct heating source to acquire the shape memory features. In addition to enhance the frequency of the actuators, a capacitor will be attached for a faster heating response along with above-mentioned cooling methods that resulted in larger device shape [127]. Another problem to be mentioned that the complexity of the control system that found due to the large numbers of actuator were employed to increase the robots DOF.

Another significant implementation for shape memory as absorbers in bridges that been effectively used [128, 129]. According to the study was carried out by European Union on the earthquake damages and the way of finding a sustainable technology to prevent the disaster damage via seismic vibration. A research was conducted for as modeling for four story building, which was constructed using the tendons techniques to minimize the earthquake possible damage, where it was found that the building without SMA was completely destroyed while the incorporated building with SMA got less damage, whereby, the implemented tendons were used to absorb energy based on the shape memory feature of super-elastic behavior and reduced the shocked waves of earthquake.

### **6. Summary**

In this chapter the characteristic of shape memory alloys in terms of microstructure, mechanical properties and thermal cyclic stress-strain curves of Cu-Al-Ni SMAs. The main benefits of these alloys can be obtained after the modifications were made, as, for a certain application, the selective of shape memory alloys

required the main consideration in term of manufacturing cost and performance, thus the Cu-Al-Ni SMAs have been shown interested attentions due to their low cost compared with Ti-based shape memory alloys. However, many researchers have faced a challenge when Cu-based shape memory materials are used for in many applications, due to their limitations such as the high brittleness and low recovery strain, thereby these properties need to be improved. Therefore, modifying the microstructure and the phase characteristics via adding the alloying elements may represent a more significant solution. The addition of the fourth element to the ternary alloy of Cu-Al-Ni SMA is able to alter the structure and/or morphology of the martensitic phase and thus improve the mechanical properties.
