While the use of metadiscourse in L2 writing has received considerable attention in the past, little effort has been made to examine how L2 writers' use of metadiscourse in academic writing has evolved over time. In addressing this, the present study explored a diachronic evolution of interactional metadiscourse in research articles (RAs) published across a span of 40 years (1980-2021) in "English Teaching." Based on 931 articles consisting of 6.4 million words, we examined whether the use of interactional metadiscourse has changed over the past 40 years. Our findings revealed that there was a global decrease in interactional metadiscourse over the past 40 years. While the frequency and diversity of interactional metadiscourse have slightly decreased over time, the proportion of each metadiscourse category remained consistent. The study further suggests that Korean L2 scholars who publish in "English Teaching" tend to hedge more than they boost or use attitude markers compared to those who publish in global journals.