ABS metalizing and tensile strength growth

Does anybody know/hear why such extra tinsile strength after ABS metalizing?

For example: Cu 30E-3 mm + Ni 15E-3 mm + Cr 0.3E-3 mm and by ASTM D638

before 37.8 Mpa, after metalizing 50.2 Mpa.

Regards -- Jack Zagaja