Tensile properties of cast and mushy state rolled Al–4·5Cu alloy andin situAl4·5Cu–5TiB₂composite

Abstract

A comparative study has been carried out on tensile properties and failure mechanisms of Al-4?5 wt-%Cu alloy and in situ Al-4?5Cu-5TiB 2 composite in as cast or mushy state rolled conditions. For the alloy, mushy state rolling at temperature for 30 vol.-% nominal liquid content to 2?5% thickness reduction leads to marginally higher strength but poorer ductility, while both these properties worsen significantly on 5% reduction because of grain growth and intergranular solute segregation. Contrarily, mechanical properties of the composite are significantly improved on mushy state rolling at temperatures for 10-30 vol.-% liquid to 2?5-5% reduction. Improvement in mechanical properties of the composite on mushy state rolling is attributed to evolution of globular and finer grains. Examination of fracture surfaces by scanning electron microscope has shown evidence of ductile failure in as cast alloy and in cast or mushy state rolled composite, but that of brittle failure in mushy state rolled alloy.

Effect of mushy state rolling on age-hardening and tensile behavior of Al–4.5Cu alloy and in situ Al–4.5Cu–5TiB2 composite

“…However, the unmelted solid skeleton undergoes repeated fragmentation and dynamic recrystallization, leading to the reduction in average grain size. A combination of SEM image and EDS X-ray maps of Ti and Cu has been shown for ACC, MRC and PHMPR2 in Figs [24,26] has been attributed to localized enrichment of Cu in liquid Al during soaking at the mushy zone temperature. This liquid is trapped either at the grain boundaries or inside the grains of ␣-Al, and undergoes rapid solidification in course of passage through the roll gap.…”

Effect of age-hardening on dry sliding wear behavior of mushy state rolled in-situ Al-4.5Cu-5TiB2 composites

“…Moreover, both wear and mechanical properties have been found to improve significantly on mushy state rolling of this composite due to chemical homogenization, grain refinement, and work hardening of the unmelted matrix grains [41][42][43][44]. In addition, both rate of agehardening and peak-age hardness have been found to be significantly higher for the mushy state rolled composite than those for either as-cast alloy or as-cast composite [18].…”

“…The samples were pushed into the roll-gap using a hollow push rod having a chromel-alumel thermocouple wire inside, the tip of which was kept in contact with the back of the specimen, such that the temperature just before their insertion into the roll gap could be ascertained accurately. The process of mushy state rolling has been described in greater detail elsewhere [41][42][43][44]. The samples were subjected to 5% reduction in thickness at a constant roll surface velocity of 0.28 ms À 1 .…”

“…The aforementioned composite was subjected to two mushy state roll passes at the temperature corresponding to 20 vol% liquid with 5% thickness reduction per pass after prior hot rolling. This condition of mushy state rolling has been chosen based on the results of an earlier study indicating that the composite processed in this manner show optimum mechanical and wear properties [43,44], which could be further improved by age-hardening heat treatment [18].…”

Quality Enhancement of TIG Welded Al6061 SiCp Composites by Age Hardening Process

“…This is mostly due to the creation of strain localisation at the sharp places of the SiC particles. The coalescence of the voids was taking place in the course of tensile loading causing the development of Void Nucleation Growth (VNG) failure at the fractured area during severe crack propagation [10][11][12][13][14] around the weaker matrix grain. Corresponding EDAX analysis shown in Figure 4 The peak aged composite shows mixed mode fracture similar to as-weld condition as shown in Figure 5(a) to 5(b).…”