  La(Fe,Mn,Si)13 alloys are a promising material family for magnetic
refrigeration. Challenges associated with their structural integrity during
device assembly and operation requires deep understanding of the mechanical
properties. Here we developed a workflow to quantitatively study the fracture
properties of La(Fe,Mn,Si)13 plates used in magnetic cooling devices. We
employed microstructural characterisation, optical examination of defects, and
four-point bending tests of samples with known defect sizes to evaluate their
mechanical performance. We established the residual strength curve which
directly links observed defects to mechanical strength. The estimated fracture
toughness KC of hydrogenated La(Fe,Mn,Si)13 is approximately 4 MPa m^1/2 for
the geometry employed. The established relationship between strength and crack
length enables the prediction of mechanical performance through examination of
defects via optical microscopy, therefore can be used industrially for
directing plate selection to guarantee the mechanical stability of
refrigeration devices.
