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The creep deformation and damage mechanism of compacted graphite cast iron (CGI) with varying pearlite contents were studied at 450 °C, 500 °C, and 550 °C, with accompanying stress ranges from 40 MPa to 150 MPa. The creep deformation of CGI alloys presents obvious when the temperature exceeds 450 °C. The creep rate exponentially decreases with pearlite contents and the creep mechanism changes from dislocation slip to grain boundary sliding. There are (Ⅰ) intergranular and transgranular cracks, (Ⅱ) interfacial debonding between graphite and matrix, and (Ⅲ) pearlite morphologic transforming in the microstructure of CGI during the creep test. (Ⅰ) and (Ⅱ) are mainly caused by the creep stress and temperature, and (Ⅲ) may be related to plastic deformation. These cracks can interact with each other and accelerate the failure and fracture of materials.

The present study investigated microstructural evolution and changes in tensile properties of an Al-Si piston alloy subjected to thermal exposures at 250 and 350 °C for 150, 300, and 500 h. Microstructural and nanoscale precipitates were characterized using a combination of high-angle annular dark field-scanning transmission electron microscopy (HAADF-STEM) images and scanning electron microscopy (SEM). The tensile testing was performed. The results demonstrated that the thermal exposure induced granulation of the δ-Al3CuNi particles, alongside precipitation of the θ-Al2Cu phase particles and AlCu clusters within the matrix. Specifically, an increase in the size and number density of the θ-Al2Cu phase particles was observed with exposure time at 250 °C. Conversely, at 350 °C, the θ-Al2Cu particles exhibited a gradual increase in size with prolonged thermal exposure, coupled with a decrease in their number density. AlCu clusters precipitated solely at a thermal exposure temperature of 350 °C, with precipitation intensifying over time. Moreover, a decrease in the alloy's tensile strength and an increase in elongation were noted after thermal exposure. Finally, the present study discussed the precipitation mechanisms of θ-Al2Cu particles and AlCu clusters within the grains, suggesting that the AlCu clusters exerted a more effective strengthening effect compared to the θ-Al2Cu particles. [ABSTRACT FROM AUTHOR]

The tension-tension fatigue test of the compacted graphite cast iron (CGI) alloy was carried out by RDL100 universal testing at 500 °C and 550 °C, respectively. A tension-tension trapezoidal load is applied to the CGI specimen. Because of the time-dependent deformation at elevated temperatures, the stress–strain curve presents hysteresis loops, and the area of the hysteresis loop increases gradually with continuous cyclic loading and sustained loading times. Intergranular and transgranular cracks in the microstructure accelerate the CGI alloy fracture failure. The fatigue life is sensitive to the short loading time and decreases with the sustained loading time exponentially under the tension-tension fatigue condition. The short holding time has a great influence on the fatigue life of CGI. The fatigue behavior of CGI alloys and the influence of holding time on the fatigue life can be characterized by y = aexp(bx) (a and b are constants, can be fitted through the test data). In addition, the fatigue life of CGI alloy can be predicted by the ductility depletion method. But the equivalent stress amplitude needs to be modified to eliminate the effects of oxidation damage.

AlN particle–reinforced Mg–Al matrix composites are fabricated by introducing an Al–AlN master alloy in Mg melt during casting. The microstructure, tensile strength, and fracture behavior of the AlN/AZ91 composites are investigated. The introduction of AlN results in a modified dendrite morphology of the β‐Mg17Al12 phase and, thus, improves the mechanical properties of the AZ91 alloy. The results show that 2% (by weight) AlN reinforcement has the highest tensile strength and elongation, mainly due to the reduction of the size of the second phase and the uniform distribution. Consequently, compared to as‐cast AZ91 alloys, the strength and elongation of the AlN/AZ91 composites increase by 34% and 171%, respectively. For second‐phase β‐Mg17Al12, the enhancement mechanism and size model are constructed, and the model trends are analyzed, predicted, and verified experimentally. [ABSTRACT FROM AUTHOR]