Structural and thermodynamical study of Cu-Zn-Al shape memory alloys with new compositions produced by hot isostatic press (HIP)

Abstract

Hot isostatic press (HIP) is an advanced kind of powder metallurgy production technique which prevents vaporization loss of alloying elements with low melting points during melting. In this work, ternary Cu-Zn-Al shape memory alloys (SMAs) withnew chemical compositions were fabricated by using hot isostatic pressing technique,then the obtained alloys were homogenized at 900 °C and quenched in iced-brine water to surpass the formation of hypo-eutectoid precipitations and lead to the formation of β’1 martensite phase in the alloy. Then the small specimens of the alloy were undergone through thermal and structural measurements. The thermograms obtained from differential thermal analysis measurements of the alloy by DTA instrument demonstrated the characteristic hysteresis curves and peaks of martensitic phase transformations which indicated the shape memory effect (SME) property exists in the alloy. The start and finish temperatures of phase transitions and some other thermodynamical parameters were determined by using the data of these thermal measurements. The structural XRD analysis made in room conditions showed the patterns of martensitic structures. The average crystallite size of the alloys were computed by using XRD data. The valence electron concentration (VEC) value of the alloys were also calculated, since it is a pre-conditional and hypothetical sign of having SME property. Furthermore, the effect of HIP production technique on these new Cu-Zn-Al SMAs was discussed.Hot isostatic press (HIP) is an advanced kind of powder metallurgy production technique which prevents vaporization loss of alloying elements with low melting points during melting. In this work, ternary Cu-Zn-Al shape memory alloys (SMAs) withnew chemical compositions were fabricated by using hot isostatic pressing technique,then the obtained alloys were homogenized at 900 °C and quenched in iced-brine water to surpass the formation of hypo-eutectoid precipitations and lead to the formation of β’1 martensite phase in the alloy. Then the small specimens of the alloy were undergone through thermal and structural measurements. The thermograms obtained from differential thermal analysis measurements of the alloy by DTA instrument demonstrated the characteristic hysteresis curves and peaks of martensitic phase transformations which indicated the shape memory effect (SME) property exists in the alloy. The start and finish temperatures of phase transitions and some other thermodynamical parameters were determin...