Abstract
Microstructural and cavitation erosion testing was carried out on Cu-12.8Al-4.1Ni (wt. %) shape memory alloy (SMA) samples produced by continuous casting followed by heat treatment consisting of solution annealing at 885 °C for 60 min and, later, water quenching. Cavitation resistance testing was applied using a standard ultrasonic vibratory cavitation set up with stationary specimen. Surface changes during the cavitation were monitored by metallographic analysis using an optical microscope (OM), atomic force microscope (AFM), and scanning electron microscope (SEM) as well as by weight measurements. The results revealed a martensite microstructure after both casting and quenching. Microhardness value was higher after water quenching than in the as-cast state. After 420 min of cavitation exposure, a negligible mass loss was noticed for both samples. Based on the obtained results, both samples showed excellent cavitation resistance. Mass loss and morphological analysis of the formed pits indicated better cavitation resistance for the as-cast state (L).
Highlights
Among the variety of advanced materials with exceptional properties and applications, shape memory alloys (SMAs) have a unique ability to return to previously defined shapes or sizes if subjected to the relevant thermal treatment
Optical Microscopy The surface of specimens was tested by trinocular metallurgical microscope (EUME, EU Instruments, Gramma Libero, Belgrade) using different magnitudes to analyze the effect of the surface erosion
Martensite appears primarily as needle-like martensite. This microstructure consists of self-accommodating needle-like shape β 1 martensite in ascast state and after heat treatment
Summary
Among the variety of advanced materials with exceptional properties and applications, shape memory alloys (SMAs) have a unique ability to return to previously defined shapes or sizes if subjected to the relevant thermal treatment. The memory effect can be reached only in the presence of specific phase transformation, reversible austenite to the martensite phase. The conditions necessary for such phase transformation include mechanical (loading) or thermal (cooling and heating) methods. There are several basic types of SMAs, such as Ni-Ti (nitinol), Cu-based, and Fe-based alloys [1,2]. All of the above types have advantages and disadvantages, while economical aspects such as the price can be very important for material selection and application. These alloys (Cu-Al-Ni alloys) can be applied in various industrial fields, especially when high transformation temperatures are required (near 200 ◦C), thanks to their high thermal stability and high transformation temperatures
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