Effects Of Elevated Temperature Exposure Research Articles

Effect of elevated temperature exposure on the structure, stability, and mechanical behavior of aluminum-stainless steel composites

The effect of elevated temperature exposure on subsequent ambient temperature tensile behavior of aluminum-stainless steel composities (V f= 6.5 pct) has been studied. In particular, ambient temperature tensile yielding, flow, and fracture were correlated with the associated interface microstructures, matrix substructure, and fracture morphology in the as-pressed condition and following elevated-temperature exposure at 550°C (823 K) or 625°C (898 K) for 24 h (86.4 ks). Compared to the as-pressed condition, exposure at either temperature results in a small increase (≲4 pet) in initial modulus, and a decrease in the level of residual stress (tensile) in the matrix; tensile stress-strain behavior in stage II (matrix plastic, reinforcement elastic) is essentially unaffected. Lower strength levels in stage III (matrix and reinforcement plastic) after exposure are due to premature cracking in the interface reaction zone, primarily a ternary (Fe, Cr) Al intermetallic, with associated notch effects on the wire reinforcement. Changes in fracture surface morphology of the composites confirm the degradation. Wires extracted from composites after hot pressing or following exposure at 550°C (823 K) possess a unique strength. Exposure at 625°C (898 K) leads to a bimodal distribution in the strength of extracted wires. In each condition, a matrix dislocation cell structure develops in stage III; the invariant form and size of the cell structure withV f and distance from the matrix wire interface confirm isostrain conditions.

Elevated Temperature Properties of Maraging Steel Plates and Welds

The creep rupture behavior, and the effects of elevated temperature exposure in air and hydrogen on the subsequent room temperature properties of a 12 percent Ni-5 percent Cr-3 percent Mo maraging steel are described. Tests have been made on several heats of plate and on gas tungsten-arc, gas metal-arc, and electroslag welds. On the basis of the results obtained, maraging steels offer promise as high-strength steels for service at elevated temperatures.

Tensile Properties Affecting the Formability of Aluminum-Alloy Sheet at Elevated Temperatures

Tensile Properties Affecting the Formability of Aluminum-Alloy Sheet at Elevated Temperatures