# Accumulative Roll Bonding--A Review
## 4 Properties
### Strength and Ductility
#### 4.1.3 Sheets with Reinforcements  
Metal matrix composites (MMCs) can be synthesized using ARB method by placing reinforcing agent between the sheets. [PERSON] et al. [12] initially used ARB to produce Al foams by dispersing particles between Al sheets. [PERSON] et al. [98] and [PERSON] [53] used ARB to produce MMCs. [PERSON] et al. [99] produced Al/Al\({}_{2}\)O\({}_{\text{Sp}}\) cast composite and [PERSON] et al. [100] fabricated Al/SiC\({}_{\text{P}}\) composite, both reporting simultaneous enhancement in strength and ductility with increasing ARB cycles. It should be noted that strengthening mechanisms of the ARBed composites are not exclusively limited to those mentioned earlier for other types of ARB, i.e., ARBed similar or dissimilar sheets; however, they are also attributed to the following items:  
* Reinforcement particles acting as barrier against dislocation movement. The first mechanism is the strengthening effect since adding reinforcements to a metal matrix significantly improve mechanical strength due to dislocation pile up around the particles [101; 102].
* Improved uniformity of reinforcements. When the reinforcement distribution becomes more uniform and homogeneous, the stress concentration sites reduces enhancing the mechanical response [103; 104].
* Improved bonding quality at the matrix/particle interfaces. Regardless of volume fraction, size, shape and the spatial distribution, the mechanical property greatly depends upon how well externally applied load is transferred to reinforcing materials, i.e., stronger interfacial adhesion enhances load transfer capacity leading to improved mechanical performance [105]. Better interfacial adhesion may be obtained through increasing ARB cycles [53]. Also, porosity may have detrimental effects on bonding quality between the reinforcing agents and the host matrix where the interfacial adhesion may be lowered by porosity causing interfacial debonding. When pores are located at the particle-matrix interface, particles are debonded from the matrix even  
Figure 14: (**a**) Variation of stress–strain curves of the ARBed Cu/Zr materials versus ARB cycles; elongation increases up to six cycles [91], (**b**) engineering stress–strain curves for starting Al, ARBed pure Al after sixth cycle and Al/Cu\({}_{\text{P}}\) composite within different cycles of ARB process [97].  
under low stress [106]. Last but not least, porosity tends to reduce effective cross-section area and hence adversely affect mechanical strength [107].  
Using reinforcing particles in the ARB process has an ability to enhance mechanical strength. For instance, [PERSON] and [PERSON] [97] compared ARBed Al/Cu\({}_{\text{P}}\) with monolithic Al where a significant improvement in both strength and ductility was observed (Figure 14b). Increasing ARB cycles further enhanced strength and ductility due to increased adhesion strength between the Al matrix and Cu particles. Moreover, the ARB process boosted the uniformity of Cu clusters and could limit the porosity as confirmed by microstructural investigation. Similar trend was seen for the ARBed Al 5083/SiC\({}_{\text{P}}\)[108], Al-Al\({}_{2}\)O\({}_{3}\)/SiC\({}_{\text{P}}\)[59; 109], Al-Al\({}_{2}\)O\({}_{3}\)/B\({}_{4}\)C\({}_{\text{P}}\) hybrid composite produced by anodizing [110], coated Al-Cu-25 Ni/SiC\({}_{\text{P}}\)[111], Al-Al\({}_{2}\)O\({}_{3}\)/ZrC\({}_{\text{P}}\)[112], Cu/Graphene\({}_{\text{P}}\)[113] and Al/Al\({}_{2}\)O\({}_{3\text{P}}\)[114] where significant strength improvement as well as increased ductility are simultaneously reported. According to [PERSON] et al. [115], alumina particles enhance the YS, UTS and the elastic modulus, but the elongation falls drastically attributing mostly to plastic zone created around the reinforcing particles.