Evolution of the microstructure and mechanical properties of Mg-matrix in situ composites during spark plasma sintering

Biomedical Mg-matrix in situ composites were fabricated from Mg and ZnO powder via ball mixing and spark plasma sintering. XRD analysis indicated that in situ reactions occurred during sintering process producing MgO, Zn and Mg–Zn intermetallic compounds. The formation of in situ products strongly contributed to the enhancement of the strength and the ductility of the fabricated composites compared with pure Mg. Specifically, the highest strength at 380?MPa was observed in the Mg-20 wt-% ZnO composite, and the highest failure strain at 12.9% was achieved in the Mg-5 wt-% composite compared with the 156?MPa strength and the 10.2% failure strain of pure Mg. In addition, the strengths of as-produced composites are as double as that of cortical bones. With these superior mechanical properties, the fabricated composites are considered as very potential candidate for biomedical load-bearing applications.     

Distinguishing the influence of aluminium and vanadium additions on microstructural evolution and densification behaviour during the sintering of ti6Al,ti4V and ti6al4v

In this work, the influence of pure Al (Ti6Al) and V (Ti4?V) powder additions on the sintering behaviour of a coarse CP-Ti powder compact was investigated. Pure Al melts and spreads to form intermetallic layers at the CP-Ti surface, causing swelling and prevention of sintering and shrinkage below 1050°C. Ti4?V compacts do not swell and begin to sinter at 990°C. The sinter rate for both Ti4?V and Ti6Al are similar at 1200°C and higher than the CP-Ti compact alone. Aluminium melting distributes this element better than the dispersed V particles, leading to more rapid homogenisation. When both pure Al and V are present (Ti6Al4?V), the sintering rate at 1200°C is similar to that of Ti6Al and Ti4?V. However, swelling is increased and homogenisation is slower, resulting in a reduced sintering aid effect compared to Ti6Al and Ti4?V.     

Effects of powder material and process parameters on the roll compaction,sintering and cold rolling of titanium sponge

ABSTRACT

Roll compaction is a powder metallurgy process that has the potential for cost reduction in the production of titanium parts. In this study, experiments were carried out to investigate the effects of powder type and size on the roll compaction and subsequent sintering and cold rolling behaviour of titanium powder. Powders used ranged in upper sieve sizes from 0.15 to 3?mm. Strip density was found to increase with decreasing powder size while thickness decreased. Following sintering in the range of 800–1200°C, cold rolling was performed with various levels of thickness reduction. Average (across the width) densities of up to 88% were achieved, with higher density regions in the middle of the strips reaching up to 99%. Roll force was measured during cold rolling and found to increase with increasing final (post-cold rolling) density and also with increasing roll gap reduction amounts.     

An experimental investigation on the assimilation and recovery of strontium–magnesium alloys in A356 melts

The assimilation of cylindrical specimens, manufactured with various proportions of strontium, magnesium, and aluminum, into A356 aluminum alloy melts was investigated. These cylindrical specimens were made as Sr–Mg binary alloys and subsequently as Sr–Mg–Al ternary alloys. Experimental details on the making of these cylinders are presented. A unique melting and casting apparatus was build to melt, mix and cast the reactive metals: strontium and magnesium.Among the various Sr–Mg and Sr–Mg–Al alloys examined the ternary ones, namely 50/25/25 Sr/Mg/Al and 60/20/20 Sr/Mg/Al, exhibited the highest recoveries in the liquid A356 aluminum alloy. In both alloys these high recoveries were observed at 725 °C. The estimated recoveries at this temperature are comparable to that of pure strontium modifier.