Elevated Temperature Tensile Creep Behavior of Aluminum Borate Whisker-Reinforced Aluminum Alloy Composites (ABOw/Al–12Si)

Abstract

In order to evaluate the elevated temperature creep performance of the ABOw/Al–12Si composite as a prospective piston crown material, the tensile creep behaviors and creep fracture mechanisms have been investigated in the temperatures range from 250 to 400 °C and the stress range from 50 to 230 MPa using a uniaxial tensile creep test. The creep experimental data can be explained by the creep constitutive equation with stress exponents of 4.03–6.02 and an apparent activation energy of 148.75 kJ/mol. The creep resistance of the ABOw/Al–12Si composite is immensely improved by three orders of magnitude, compared with the unreinforced alloy. The analysis of the ABOw/Al–12Si composite creep data revealed that dislocation climb is the main creep deformation mechanism. The values of the threshold stresses are 37.41, 25.85, and 17.36 at elevated temperatures of 300, 350 and 400 °C, respectively. A load transfer model was introduced to interpret the effect of whiskers on the creep rate of this composite. The creep test data are very close to the predicted values of the model. Finally, the fractographs of the specimens were analyzed by Scanning Electron Microscope (SEM), the fracture mechanisms of the composites at different temperatures were investigated. The results showed that the fracture characteristic of the ABOw/Al–12Si composite exhibited a macroscale brittle feature range from 300 to 400 °C, but a microscopically ductile fracture was observed at 400 °C. Additionally, at a low tensile creep temperature (300 °C), the plastic flow capacity of the matrix was poor, and the whisker was easy to crack and fracture. However, during tensile creep at a higher temperature (400 °C), the matrix was so softened that the whiskers were easily pulled out and interfacial debonding appeared.

Recent Progress in Creep-Resistant Aluminum Alloys for Diesel Engine Applications: A Review

“…Ji et al [40] evaluated the creep performance on Al-12Si alloy reinforced with borate whiskers (Al18B4O33) and unreinforced Al-12Si alloy at 250-400 °C and 50-230 MPa. Creep resistance in the reinforced alloy was improved by three orders of magnitude, compared with the unreinforced alloy.…”

“…Al-Cu alloys [33][34][35][36], metal-matrix composites [37][38][39][40][41][42][43][44][45], and additively manufactured aluminum [46][47][48][49][50][51][52] can be used as selective reinforcement materials. Nano-structured aluminum [60][61][62][63][64][65][66][67][68][69] can be used as inserts to improve the creep resistance of the aluminum diesel engine in the inter-valve zone if the thermal stability can be improved.…”

Research on the Secondary Forgeability of High Volume Fraction Whisker Reinforced Aluminum Matrix Composites of Original Squeeze Casting

“…Metal matrix composites (MMCs), especially those based on light metals such as aluminum alloys, have become an indispensable lightweight structural material in high-tech areas such as defense aerospace and military equipment due to its advantages of light mass, high strength, well thermal stability, wear resistance and low thermal expansion coefficient [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 ]. However, MMCs have low elongation, poor plastic forming ability and low material utilization, making it difficult to form complex parts, which is the most important reason to limit their application [ 13 , 14 , 15 , 16 , 17 , 18 , 19 ].…”