The effects of Friction Stir Processing (FSP) on the hardness of Al-Cu binary alloys with various copper contents up to 9mass%Cu were investigated. Prepared Al-Cu samples were divided in two groups. Samples in one group were used as cast sample plate. Samples in the other group were annealed at 673K for 108ks. The hardness of as cast samples increased with increasing copper content before FSP treatment. The hardness of the annealed samples increased in the same way as the as cast sample at low copper ranges up to 5mass%Cu. At higher copper content ranges from Al-5%Cu, the rate of hardness increment of annealed samples however slowed down before FSP. Sample plates were treated by FSP, and microstructure and hardness were measured. Samples containing less than 4%Cu including pure aluminum showed hardness increment by 10HV after FSP regardless of heat treatment. For as-cast series specimens however, the FSP treatment never increased the hardness in copper content ranges from 5mass% to 9mass%. On the other hand, annealed samples were slightly hardened by FSP. This is because the annealed samples have a weaker network of harder phase than as-cast samples, and the breakdown of such networks and distribution of the fragments weaken the material of as-cast samples.

  The purpose of this study is to investigate the effects of humidity on the strength characteristics in high strength spheroidal graphite cast iron with two phases, which is ferrite and pearlite. Three spheroidal graphite cast irons (FCD400 (FDI), FCD500 (FPDI.82) and FCD600 (FPDI.55)) were used as specimens. In addition, heat treatment (Normalizing) was conducted in FCD500 (PDI). Tensile test conforming to JIS was carried out using these resultant four materials in air and water. The specimen used was of the 14A type. The relationship between tensile strength and area ratio of brittle fracture was investigated. Fatigue crack propagation test conforming to ASTM was also carried out using these materials. Stress ratio R was 0.1, and the specimen used was of the 1CT type with a thickness of 12.5mm. The test was carried out at room temperature and three kinds of humidity : 0, 40, and 80%. The relationship between the characteristics of fatigue crack propagation and crack closure generated on the fracture surface was investigated.

  Though tensile strength in FDI and FPDI.82 was not influenced by water brittlement, strength in PDI and FPDI.55, which included pearlite, was decreased by water brittlement. This phenomenon may mainly be caused by the amount of pearlite in the matrix. The threshold stress intensity factor range ΔK_th of all materials increased with increasing humidity. Crack closure was investigated in all materials. It seemed to become marked with increasing humidity. In the low ΔK_eff region of all materials (except FPDI.55, 80%), the fatigue crack propagation rate was almost the same because of oxide-induced crack closure of the ferrite included in the matrix. In the high ΔK_eff region of FPDI and PDI, the rate was not the same. The acceleration was investigated because of effects of a phenomenon similar to the water embrittlement of pearlite included in the matrix.

  Electromagnetic acoustic resonance (EMAR) and magnetic hysteresis loop (MHL) measurements were performed in cast irons with different graphite morphology and matrix structures. The ultrasound transverse velocity, ν_t proportionally increased with increasing tensile strength in flake graphite cast irons (FC), whereas it was almost constant in spheroidal graphite cast irons (FCD). The coercive force, Hc of MHL was proportional to the tensile strength in FCD with different pearlite fraction in the matrix. The combination of the two techniques utilizes the advantages and compensates for the weaknesses of each technique. Based on the relationship between micro-structures and the physical parameters (ν_t and Hc), a simple model for estimating tensile strength was proposed. This study demonstrates the feasibility of the combined electromagnetic techniques for the non-destructive evaluation of tensile strength in cast irons.

  The mechanical properties of ductile cast iron are affected by casting thickness and casting conditions. The thinning of casting walls increases the effects of thickness on the mechanical properties. Nondestructive evaluation of mechanical properties is required to optimize the strength design of ductile cast iron castings. Several attempts have been made to apply the eddy current method for evaluating matrix and mechanical properties of ductile cast iron. However, surface conditions such as surface roughness and residual stress affect eddy current signals.

  This research deals with the effects of surface machining on the eddy current evaluation of ductile cast iron. Ductile cast iron specimens of two types of matrix with different surface roughness were prepared. Specimens were cut from the Y-block of about 40mm in width, and the surface was machined using a shaping machine and two types of cutting conditions. Half of the specimens were annealed in nitrogen gas atmosphere. Measurements of eddy current signals Vx, Vy were performed using an eddy current instrument.

  The eddy current signal varied with ductile cast iron matrix and was affected by surface roughness. The relations between the eddy current signals and matrix and surface conditions showed dependence on testing frequency. The testing frequency of 25kHz was suitable for distinguishing the effects of surface roughness from the effects of matrix. 50kHz also can be applied by phase change. There were correlations between Vx and surface roughness Ra and Rz, Vy and matrix, respectively. Changes in the eddy current signal due to the surface roughness showed similarity with the changes by the liftoff of the probe. Annealing affected the signals Vx and Vy, suggesting that residual stress induced by cutting was relieved. The matrix of the ductile cast iron can be estimated by the eddy current method even with different surface roughness, but a suitable testing frequency should be chosen and the residual stress should be taken into consideration.

  Generally, silicon steel material is used for the electromagnetic yoke in motors. In recent years, cast iron with high permeability is being developed and its application as yoke material is considered. During the shrinkage fitting process of motors, compressive stress is applied to the electromagnetic yoke. As this decreases magnetic properties, methods for inspecting compression stress in the manufacturing process of motors is required. When cast iron is compressed, permeability decreases. Similarly, the permeability of the magnetic yoke in the motor changes when compressed stress is applied. This means that the compressive stress of cast iron can be inspected by observing the changes in the magnetic properties of the cast iron.

  In this paper, the authors propose a small electromagnetic inspection sensor capable of measuring the compressive stress inside cast iron magnetic yoke in motors. The compressive stress in the cast iron when the cast iron magnetic yoke is compressed by shrinkage fitting was calculated by 3-D stress analysis using the finite element method (FEM). The size of compressive stress inside cast iron can be obtained by evaluating the flux density inside the cast iron using 3-D nonlinear electromagnetic FEM taking into account electromagnetic properties under various compressive stresses.

  Since the permeability of cast iron changes according to the compressive stress, compressive stress in cast iron can be evaluated by detecting the change in flux density using electromagnetic inspection. However, the flux signal is also influenced by the change in distance (lift-off : L_o) between the cast iron and proposed electromagnetic inspection sensor.

  In this study, we also show that compressive stress in cast iron can be estimated by detecting the changes in the amplitude and phase difference in the flux density in a search coil of the proposed inspection sensor. We also conducted experimental verification considering the effects of lift-off.

  Chills tend to generate easily in thin wall spherical graphite cast iron. Because chill is a hard and brittle structure, chill structures contained in cast iron decrease the mechanical properties of cast iron considerably, especially toughness. However, it is difficult to detect the existence of chills in cast iron by visual observation, and sometimes they may remain undetected in good cast iron products shipped out. In the present study, a non-destructive inspection method for detecting the existence of chills in cast iron instantaneously was reviewed by investigating the relationship between ultrasonic wave propagation factors (e. g. : ultrasonic velocity, propagation time, thickness of casting, etc.) experimentally. It was found that chills in the cast iron can be detected using virtual thickness S4 which is calculated from the 4th bottom echo of the ultrasonic pulse-echo method with constant ultrasonic speed and casting thickness.

  An ultrasonic detection method for casting defects existing near the surface of die castings was developed. The surface acoustic wave (SAW) was measured with cast plates containing an alumina thin plate, measuring 0.2mm in thickness and 2mm in width, to simulate the oxide layer of the cold flake. The SAW intensity reflected from the alumina thin plate existing at a depth of 0.7mm or less was detected. The reflected SAW intensity increased with decreasing distance from the alumina thin plate, and became maximum just before the alumina thin plate. Next, the SAW intensity was measured by irradiating at different angles from the surface normal to the alumina thin plate. Finally, the mapping image of the alumina thin plate was obtained by moving the SAW probe parallel to the alumina thin plate.