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  • Shape memory alloy transformation temperature

    Table: Shape memory alloy and their Transformation temp range

    Alloy Transformation range (degree C)
    Ag-Cd -190 to -50
    Au-Cd 30 to 100
    Cu-Al-Ni -140 to 100
    Cu-Au-Zn -190 to 40
    Cu-Sn 15 -120 to 30
    Cu-Zn -180 to -10
    Cu-Zn-Al 0 to 150
    4-6% Al Room temperature
    In-Ti 60 to 100
    Ni-Al -180 to 100
    Ni-Ti -50 to 110
    Fe-Pd -100
    In-Ti 60 to 100
    Fe-Pt -130
    Mn-Cu -250 to 180
    Fe-Mn-Si -200 to 150


    Shape memory alloys (SMAs) are metallic alloys which can recover permanent strains when they are heated above a certain temperature. In 1931 frst shape memory alloy transformation was observed by Chang and Read. In 1963 NiTi alloy was discovered by naval ordnance laboratory.

    The key characteristic of all shape memory alloys is the occurrence of a martensite phase transformation. When an shape memory alloy undergoes a martensite phase transformation, it transforms from its high-symmetry, usually cubic, austenitic phase to a low-symmetry martensite phase, such as the monoclinic variants of the martensite phase. The most common shape memory material is an alloy of nickel and titanium called Nitinol. As an actuator, it is capable of up to 5 % strain recovery and 50,000 psi restoration stress with many cycles.

    A shape memory alloy wire with a diameter of 1mm can lift a weight of 15kg. Therefore, it has a very high force-to-weight ratio. Actually, shape memory alloys show a work density of 107 Jm-3, which is 25 times greater than the work density of electrical motors.

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