Influence of microstructural heterogeneities on small-scale mechanical properties of an additively manufactured Al-Ce-Ni-Mn alloy

•Revealed the influence of local microstructural heterogeneity at melt-pool-boundaries in additively manufactured Al-rare earth alloy on nanomechanical properties.•In situ nanoindentation and micropillar compression identified melt pool boundaries as weak spots.•Identified the reasoning for creep void coalescence and failure initiation from melt pool boundaries.