Abstract: [Purpose/Significance] This study aims to reveal how the impact of Altmetrics research diffuses from within a single discipline to other fields and beyond academia, thereby deepening comprehensive understandings of this domain and promoting altmetrics research to better serve disciplinary development and societal needs.[Design/Methodology] Altmetrics-related literatures and their citation data published between 2010 and 2024 are retrieved from the Web of Science Core Collection, along with corresponding altmetrics data from the Altmetric.com database. Adopting two dimensions, interdisciplinarity and expansion beyond academia, which correspond to two levels of impact（within academia and outside academia）, this study utilizes bibliometrics, thematic analysis, and case studies to uncover the cross-boundary impact generated by Altmetrics and the processes through which they unfold. [Findings/Conclusion] The results show that publications concerning Altmetrics originating outside the field of Information Resource Management account for up to 70% of all Altmetrics literature, and citing documents from outside IRM constitute up to 82% of all citations. Furthermore, the breadth, intensity, and speed of knowledge output from Altmetrics research have continuously increased. The most frequent citation motivation for citing Altmetrics work is discussion, and the most common themes of citing articles focus on impact evaluation, hot-spot identification, and scholarly communication. Altmetrics has outstanding performance in social media, news and policy, and has demonstrated a unique mechanism for forming its cross-boundary impact. These findings indicate that altmetrics research, as an important subfield of IRM, has garnered widespread attention and exerted a positive influence. [Originality/Value] This study provides a comprehensive quantitative disclosure of the cross-boundary impact of altmetrics research, offering a directional reference for the development of Altmetrics; while the two-dimensional analytical framework constructed in this work possesses some generalizable application value.

Keywords: Altmetrics, Social impact, Academic impact, Knowledge diffusion, Interdisciplinary influence, Out-of-circle