# Accumulative Roll Bonding--A Review
## 4 Properties
### Wear  
Wear properties can be tailored using ARB process to meet the end tribological requirements. [PERSON] et al. [125], observed that the wear rate of ARBed pure Al sheets increases gradually with ARB cycles as shown in Figure 19. The wear resistance was increased up to the third cycle due to hardness increase and then reduced due to poor strain hardening capability [126]. The wear rate increment at the first cycle can be attributed to decreasing ductility [85].  
Wear observed in samples subjected to higher ARB cycles seem to occur by the mechanisms other than those usually observed in a lower number of cycles. After the third cycle, wear rate increased progressively due to the creation of high energy and unstable grain boundaries and high angle grain boundaries. These boundaries were reported to have low recrystallization temperature, they can easily rotate or coalesce when a large local strain is imposed (as in a wearing surface) leading to a rapid growth of the recrystallized grains at the subsurface. There would be a strain mismatch between the wearing surface with large recrystallized grains and the rest with non-equilibrium UFG structure. This is the cause for the delamination of the deformed layers that may result in high wear rates [126]. [PERSON] et al. [127] investigated the wear resistance of ARBed pure Al/SiC nanocomposite and  
Figure 19: Variation of wear rate versus number of ARB cycles [125].  
Figure 18: Plane stress fracture toughness of the ARBed Al 1050 specimens for different cycles [122].  
measured weight loss and friction coefficient. According to Figure 20a, it can be seen that the friction coefficient of a monolithic Al sample is larger than ARBed Al/SiC\({}_{\text{p}}\) composite and that increasing ARB cycles leads to reduced friction coefficient owing to the fact that SiC particles act as solid lubricant reducing the temperature at the contacts between the worn surface and the test pin.  
[PERSON] et al. [128] studied the wear behavior of nanostructured Al/Al\({}_{2}\)O\({}_{3\text{p}}\) composite produced by an ARB process. Figure 20b shows the variations of weight loss versus the sliding distance of ARBed monolithic and composite samples. The ARB process causes an increase in weight loss of both monolithic and composite specimens compared with as-received strip, hence reducing wear resistance. Wear resistance was also decreased with an increase in number of ARB cycles. Wear contains a combination of three mechanisms of abrasion, adhesion and delamination; at a higher number of ARB cycles, delamination remains as the main wear mechanism. The nature of laminated structure helped further delamination during the wear test and that eliminates the grain size effect on the wear resistance. Although adhesive, abrasive and delaminating wear mechanisms simultaneously happened in the composite, surface damage resulting from the plastic deformation of ARBed composite was more widespread than the monolithic material. It was shown that both delamination and spalling mechanisms occurred in the composite, while it was just the delamination mechanism that occurred in the monolithic samples.