This research focused on defects reduction in spheroidal graphite iron casting process of a jackscrew manufacturer in which graphite nodularity was lower than a given specification (75%). This situation could lead to serious issues and accident to end-users. The Six Sigma approach of DMAIC was employed to identify and eliminate the problems. The result obtained after implementing the Six Sigma showed that the process capability was improved from-0.47 to 2.04, and the average per cent graphite nodularity was increased significantly from 61.49% to 86.43%.

Open-cell nickel aluminide (Ni-Al) intermetallics foams have attracted much attention in industries at which high temperature and severe environment are concerned, due to their good physical and chemical properties. A combination of different pore structures and morphologies in a single monolithic matrix can extend the properties of a material from which a wide range of applications can be applied. In the present study, open-cell Ni-Al intermetallic foams with hierarchical porosities have been developed through a sintering and dissolution process (SDP) and reactive synthesis techniques. The carbamide particles of various contents were used as a space holder material to create macropores in the foams. Micropores were formed as the result of to the formation of initial fine pores between the powders in the compacts, the volatilization of gases evolved during reactive sintering and different diffusion coefficients between Ni and Al. After sintering, only Ni3Al is present in the matrix.Key words: Ni-Al intermetallics, metallic foam, powder metallurgy, porosity INTRODUCTIONOpen-cell metallic foams are attractive engineering materials which are effectively used in many functional applications such as heat exchanger, catalyst support, filter, sound insulator and bone-replacement implant, due to a combination of their appealing properties, including large surface area, interpenetrating porosity and high specific strength [1][2][3][4]. Among all types of open-cell metallic foams, nickel (Ni) foams have attracted much attention [5][6][7][8][9][10][11]. Application of Ni-based foams is commonly found in electronic and automotive industries as high power batteries, owing to their high capacity and safety characteristics. A recent development in hybrid electric vehicles has driven the use of Ni-based battery, such as nickel-metal-hydride (Ni-MH) as a hydrogen-storing alloy [11]. Another group of potential Ni-based foam is porous Ni-Al alloys. They have excellent oxidation and corrosion resistances due to the formation of protective -Al2O3 on the surface at high temperatures [12,13]. Due to their good physical and chemical properties, they can then be used in applications at which high temperature and severe environment are concerned.There are many processing methods to fabricate open-cell metallic foams, ranging from the utilization of base metal that started out as a liquid [14] and the employment of base metal as metallic powder [15,16]. The powder-based method has many advantages since high melting point metal and large alloying variation can be processed. Material handling also gives the ability to control size, structure, quantity, and inner cavity structure.The sintering and dissolution process (SDP) method is a simple, convenient and effective technique [15]. It is considered as one of the most widely used replication processes. It enables manufacturers to control pore architecture, morphology and dimension. The process is