Production and Characterization of AZ91-CNT Cast Nano Composites by Introducing Mg-Ni-P-CNT to the Melt Due to need for fuel savings nowadays, light metal alloys are worth considering for traortation structures. In this regard magnesium and its alloys with the least density among industrial metals have increasing scientific and industrial applications. However, magnesium has limited formability and low strength, so, development of magnesium composites are desired to reduce the mechanical property related shortcomings of this light metal and its alloys. Carbon nano-tube (CNT) with a unique atomic structure is known as a modern material with new applications. CNT has a combination of perfect mechanical, physical and electrical properties and with its extraordinary strength and high toughness is an ideal candidate for reinforcement of composite materials. Although CNT will be useful for improving magnesium properties, there are some disadvantages for production of composites reinforced by CNT. High agglomeration tendency and poor wetability of CNTs with metal melts due to their surface energy differences are the main challenges for using this modern material as the reinforcement in composites. Considering the desire to overcome these challenges, coating CNTs or putting them in a metallic coating are two practical solutions. In this study, nickel- phosphorous electroless coating process was employed for the first time for uniform co-deposition of CNTs into a Ni-P matrix coated on magnesium powder. In the first steps, important parameters of electroless bath like pH and temperature were optimized for the best condition of entangling CNTs. Then different amount of CNTs are introduced to the electroless bath for the best situation of dispersion and reinforcing. Due to very large surface area of the particles to be coated, intense coating reactions which would prevent CNT agglomeration in the coatings were expected. Also moving powder as coating surface caused a homogenous suspension of reinforcement in the electroless bath so uniform composite coating could be produced. The magnesium powder with the optimum composite coating was used as the reinforcement for uniform addition of CNTs to AZ91 alloy through mechanical mixing in the molten alloy. Similar composites were also produced with untreated as-purchased CNTs for comparison.resulted in notable grain refinement of the matrix, whereas addition of untreated CNTs were not very effective. On the other hand, one percent dispersed CNTs in the coating caused 32 percent enhancement in UTS, 16 percent enhancement in Young modulus, 23 percent enhancement in yield stress, 36 percent enhancement in hardness and 30 percent enhancement in flexural strength in comparison with the monolithic samples.
