For biomedical applications such as self-expanding vascular stents and orthopedic bone staples, the use of shape memory alloys (SMAs) is increasing. The NiTi is the most widely used SMA, but the large amount of Ni content has raised concern about Ni allergy. Recently, we developed Ni-free Co-Cr-Al-Si (CCAS) SMAs. By using <001> single crystals, a recoverable strain of about 17.0% was obtained, which is twice that of NiTi. However, the CCAS alloys suffer from a problem related to the hysteresis of the superelasticity. Upon the formation of martensite, i.e., the martensitic transformation starting stress ($\sigma_{\mathrm{Ms}}$), a clear sudden decrease of stress appears. This behavior is robust and it neither decreases nor disappears after training; instead, the sample is damaged by this behavior, thus fracture occurs after several cycles of superelasticity. Moreover, for the CCAS alloys, the superelasticity behavior has only been investigated on limited compositions, thus a full picture of the alloy system is still unclear. In this talk, we introduce our recent results focusing on the superelasticity behavior of a section of CCAS alloys with different compositions. We fabricated <001> single crystals, and both the composition and temperature dependence of the superelastic behavior were examined. Furthermore, for a selected alloy, $in situ$ neutron diffraction measurements were conducted during the tensile tests. With the aid of digital image correlation (DIC) measurements, the relation between the microstructure and crystal structure evolution was obtained during tensile tests over a wide temperature range of 100 K to 300 K. At low temperatures, it was revealed that the sudden decrease of stress upon the formation of martensite was remarkably alleviated. At the same time, some extra peaks were found from the diffraction patterns. These findings will be explained in detail in this talk.