Positron Lifetime Measurements of Subsurface Region in Aluminium Alloy and Aluminium Alloy Composite after Dry Sliding

This paper presents positron lifetime studies of the subsurface region of AK12 aluminium alloy and Al$\text{}_{2}$O$\text{}_{3}$-particle-reinforced AK12 aluminium alloy composite after sliding against steel in the pin-on-disc machine. The defect depth profile detected in the AK12 alloy extended up to 300μm but for the composite AK12 the range of this profile was significantly shortened to less than 90μm. The positron lifetime dependence on depth evidences a steep gradient of defect concentration near the surface. The subsurface zones have been also examined using scanning electron microscopy.