Minor Additions Of Zr Research Articles

Microhardness and Tensile Properties of a 6XXX Alloy Through Minor Additions of Zr

The 6XXX series alloy is known to show inferior age-hardening response during the paint-bake cycle due to natural aging prior to the paint-bake. Many researchers have adopted the pre-aging process to offset the detrimental effect of the natural aging process. The alloy used in this study contained excess Si, and it had been reported elsewhere that such alloys do not show positive response to the pre-aging process. The present work is aimed to study the microhardness and tensile strength of the Al-1.2Si-0.5Mg-0.25Fe wrought alloy through Zr additions between 0.02 and 0.30 wt.%. Alloys containing 0.15 wt.% Zr and above heat-treated for 30 min gave higher microhardness and ultimate tensile strength values compared to that of Al-1.2Si-0.5Mg-0.25Fe without Zr which was heat-treated for 11 h. It was found that mechanical properties improved when the Zr content in the alloys increased. The improvement of mechanical properties was mainly attributed to formation of Zr-bearing intermetallic compounds formed in the alloy.

Improving Fe 3Al alloy resistance against high temperature oxidation by pack cementation process

The paper presents the results of oxidation tests of Fe 3Al-based alloys containing additions of Cr, Zr, B, and C, with and without an aluminide coating. The coating was formed by a pack cementation process in which the surface of material got enriched in aluminum. The Al-rich layer was intended to enhance the tendency of Al 2O 3 formation. The slow-growing Al 2O 3 scale provides the best corrosion protection for structural materials at high temperatures. The cyclic oxidation tests were performed in laboratory air at 1373 K. The structure and composition of oxide scales as well as their adherence were evaluated and compared for the materials with and without aluminide coatings. Surface enrichment in aluminum and effect minor addition of Zr on oxidation behavior was discussed.

Improved properties of A319 aluminum casting alloy modified with Zr

The beneficial effects of 0.15 wt.% Zr addition on mechanical properties and wear resistance of A319 aluminum casting alloy were investigated. The cast alloys were given a solutionizing treatment followed by artificial aging in the temperature range 175 to 235 °C for different period of times. Mechanical properties and wear behavior of the Zr-containing material were determined and compared to those of the base A319 alloy in both as-cast and age-hardened conditions. It is shown that minor addition of Zr results in the precipitation of Al 3Zr particles in the aluminum matrix. These particles are stable upon heating due to the low solubility of zirconium in aluminum matrix. The main effects of such particles are an increase in hardness, strength, quality index and wear resistance. This is very promising where these aluminum cast alloys are to be used at relatively high temperatures.

Effects of minor additions and impurities on oxidation behaviour of FeCrAl alloys. Development of novel surface coatings compositions

In the present work the effects of single or combined minor additions of Zr, Hf, Ti and C on the oxidation behaviour of Y-containing, FeCrAl alloys have been studied. For this purpose high-purity, model alloys with single or multiple minor alloying additions were used. The results of long term discontinuous oxidation tests and detailed kinetics studies using thermogravimetry were complemented with extensive microstructural characterisation of the formed alumina scales using SEM and STEM. Hence, the oxidation kinetics and scale spallation rates and failure modes were correlated with the oxide composition and microstructure. The results demonstrate that the frequently reported positive effect of Zr, Hf and Ti on the lifetime oxidation behaviour of FeCrAl alloys can only be fully exploited if the concentrations of the above elements are carefully adjusted and the interaction with typical alloy impurities, such as carbon, is considered.

CORROSION BEHAVIOUR OF AGE HARDENABLE ALUMINUM–CHROMIUM ALLOYS

The corrosion behaviour of binary Al-Cr alloys and the ternary alloys with minor Zr additions were investigated. Immersion tests and current potential measurements were conducted with solution heat treated and aged specimens under exposure of varying levels of salinity and pH. Electrochemical corrosion parameters were evaluated from the potentiodynamic polarization plots of the binary and ternary alloys and were indicative of the relative extent of corrosion resistance in the alloys under different conditions. Results of immersion studies indicate that for binary Al-Cr alloys, the corrosion behaviour was not influenced by prior ageing temperature whereas for ternary alloys, the ageing temperature appeared to influence the corrosion behaviour. These results are further substantiated in microstructural observations from transmission electron microscopic (TEM) analysis and optical metallography was used as a supporting study to reveal the morphology of the corroded surface.On a investigué le comportement de corrosion d’alliages binaires Al–Cr et d’alliages ternaires avec additions mineures de Zr. On a effectué des épreuves d’immersion et des mesures de courant–potentiel avec des échantillons traités par mise en solution et trempe puis vieillis, par exposition à différents degrés de salinité et de pH. On a évalué les paramètres électrochimiques de corrosion à partir des courbes de polarisation potentiodynamique des alliages binaires et ternaires. Ces paramètres étaient indicatifs du degré relatif de résistance à la corrosion des alliages sous différentes conditions. Les résultats des études d’immersion indiquaient que pour les alliages binaires Al–Cr, le comportement de corrosion n’était pas influencé par la température antérieure de vieillissement alors que pour les alliages ternaires, la température de vieillissement semblait influencer le comportement de corrosion. Ces résultats sont davantage établis par les observations de la microstructure lors de l’analyse de microscopie électronique à transmission (TEM). On a utilisé la métallographie optique comme étude de support pour révéler la morphologie de la surface corrodée.

Effect of Zirconium on Microstructure and Mechanical Properties of Cast Fine-Grain CM 247 LC Superalloy

This study investigates the effect of Zr minor additions, with Zr content from 0.015 to 0.15 mass%, on microstructure and mechanical properties of fine-grain (65 mm) CM 247 LC superalloy. Tensile test results indicate that minor addition of Zr to fine-grain CM 247 LC can dramatically improve the yield strength at 300 K as well as both the yield strength and the elongation at 1033 K. Under creep conditions of 1033 K/725 MPa or 1200 K/345 MPa, the Zr additions drastically increased the rupture life, creep rate and elongation. The AES observation reveal that Zr may enrich at grain-boundary and boride/matrix interface and dissolve in matrix, carbide or � 0 phase. Thus, Zr may change the primary MC carbide characteristics and inhibit the script-like MC carbide formation. Moreover, Zr is apparently to increase the effects of the cohesive energy of both the precipitated phase/matrix interface and the grain boundaries, also it is beneficial to stress accommodation and retards the crack initiation and propagation.

Dynamic embrittlement in an age-hardenable copper-chromium alloy

Copper containing up to {approximately}1 weight % chromium is a precipitation hardening alloy exhibiting good room temperature strength, ductility and high electrical and thermal conductivity. Age-hardenable Cu-Cr alloys have been found to suffer from embrittlement in the temperature range 400--800 K. Grain boundary segregation of sulfur has been suggested to be the cause. Minor additions of Zr and Ti have been found to significantly improve the hot ductility of these alloys and this has been attributed to scavenging of grain boundary sulfur as zirconium sulfide. The mechanism of embrittlement during hot deformation processing of Cu-Cr alloy and other copper-based alloys is far from understood and efforts are continuing to understand the embrittlement process in these alloys.

Influence of minor additions of Zr on the mechanical behaviour of a Mg/1bLi/1bAl alloy

Influence of minor additions of Zr on the mechanical behaviour of a Mg/1bLi/1bAl alloy