In present research work, multi-pass friction stir processing was utilized for the as-cast Al–17%Si alloy. The multi-pass friction stir processing reproduced the aluminum (Al) matrix with a uniform distribution of the ultra-fine silicon (Si) particles. The multi-pass friction stir processing also resulted in the formation of refining cast microstructure with negligible porosity. The significant reduction in silicon particle size was measured and it reduced from 204 µm to 0.86 µm after the first pass and up to 0.30 µm after two pass friction stir processing. The frequency of fine Si particles was increased after two pass friction stir processing as compared to single pass friction stir processing. The engineering stress–strain curves revealed a significant enhancement in ductility and strength after one and two passes of friction stir processing as compared to the as-cast alloy. After one and two passes of friction stir processing, the ultimate tensile strength of as-cast alloy was enhanced by 24% and 31% ...

Ductilizing of cast hypereutectic Al–17%Si alloy by friction stir processing:

La demarche actuelle des industries aerospatiales est de diminuer le cout de lancement des engins spatiaux par une reduction de la masse des composants. Dans l’optique de cette demarche, de nouveaux materiaux sont elabores et permettent de satisfaire aux exigences de densification, de dissipation thermique et de reduction de masse des equipements electroniques embarques dans les satellites. Cette these est une contribution a l’etude de deux de ces materiaux, l’AlSi CE9F et une nuance d’alumine cofrittee a temperature, destines a realiser des boitiers hybrides de protections de composants electroniques, initialement concus en Kovar. Les objectifs sont d’affiner les connaissances sur proprietes mecaniques des deux materiaux et de mettre en place des regles de conceptions propres a leurs comportements mecaniques. En effet, l’AlSi CE9F et l’alumine ont un comportement a rupture fragile. La determination de leurs resistances a la rupture est alors realisee dans le cadre de la theorie de Weibull. Des series d’essais de flexion quatre points et trois points sont effectues. Elles permettent d’identifier les parametres de Weibull des deux materiaux a temperature ambiante et de mettre en evidence les effets de volume. L’etude experimentale est poursuivie sur l’AlSi CE9F afin de determiner l’influence de la temperature sur ses proprietes mecaniques a travers deux approches. La premiere s’interesse a une variation monotone de la temperature et la seconde a des cycles thermiques entre -50 et 125°C. Si la premiere etude ne montre qu’une faible evolution du module d’elasticite, la seconde demontre que les cycles thermiques contribuent a l’amelioration de la resistance a la rupture de l’AlSi CE9F. Cette augmentation de la contrainte a la rupture se traduit egalement par une evolution de sa microstructure. Dans un second temps, un modele de Weibull est numeriquement mis en place a partir des parametres identifies et du critere de la contrainte equivalente de Freudenthal. Ce critere est analyse et valide a travers l’etude de trois eprouvettes en AlSi CE9F a chargements complexes. Le modele valide est enfin utilise pour decrire le comportement mecanique de deux composants dans differentes configurations de sollicitation, realises respectivement en alumine HTCC et en AlSi CE9F. Une methodologie de dimensionnement est alors mise en place et permettra de disposer de nouvelles regles de conception equivalentes a celles existant sur les materiaux classiques.

Caractérisation et modélisation probabiliste de la rupture fragile de l’AlSi CE9F et d’une alumine cofrittée pour composants embarqués à applications spatiales

https://hal-mines-albi.archives-ouvertes.fr/hal-01336747/document

Probabilistic rupture analysis of a brittle spray deposited Si–Al alloy under thermal gradient: Characterization and thermoelastic sizing guidelines

The microstructural characteristics and mechanical properties of Al–6.5Si and Al–18Si alloys have been investigated. The alloys were spray-deposited and hot extruded at 480C with an area reduction ratio of 6:1. The microstructure of the spray-deposit of Al–6.5Si alloy
showed spherical morphology of the primary a-phase with a globular shape of the eutectic Si phase in the inter-particle boundaries. On the other hand, a fine particulate morphology of primary Si phase uniformly dispersed in the matrix of the a-phase was observed in spray-deposit of Al–18Si alloy. Microstructural refinement was further increased in the hot extruded alloys. The room temperature tensile tests of spray formed and extruded alloys showed considerable increase in their strength and ductility over that of the as cast alloys. The improvement in mechanical properties of spray formed alloys is discussed in light of the microstructural modifications induced during spray deposition process.

Microstructure and mechanical properties of Al–Si alloysproduced by spray forming process

https://iopscience.iop.org/article/10.1088/2631-8695/ab6b68/pdf

Direct continuous manufacturing Al–Zn–Mg–Cu alloy from a novel technology of spray-conform

Modified Al alloys are gaining emphasis in the past few years due to wide range of properties available for the
engineering applications. These alloys are manufactured by spray forming process have superior properties over the
conventional cast alloys. Hence in this article an attempt has been made to summarize the work that has been carried out in the
field of spray forming of hypereutectic Al – Si alloys and with other alloying elements such as Fe, Cu, Mg and Mn. As
hypereutectic Al – Si alloys are attractive for the industrial applications due to their low thermal expansion co – efficient and high
tribological properties. In this study attention has been paid towards the microstructure, mechanical and tribological properties of
the studied alloys. The study of process parameters over the size and shape of the powder in spray forming is other part of this
work. The change in properties of spray formed alloys by the working of secondary process is also been considered.

Spray Deposition Process of Hypereutectic Al – Sialloys: An overview

In the present study, Al-28Si, Al-28Si-5Cu-4Fe and
Al-28Si-5Cu-4Mg alloys were produced by spray forming and
subsequently hot pressed for densiﬁcation. The effect of alloy composition on the microstructure and mechanical behavior of spray-formed alloys were investigated. The microstructures consist of an equiaxed, nearly spheroidized grain morphology of α-Al matrix. The spray formed alloys exhibited sharply decreased segregation and increased metastable solid solubility and greater volume fraction of Si particles and intermetallic phases. Spray formed Al-28Si-5Cu-4Fe alloy contains Al 2 Cu,
Al 5 FeSi along with Si. On the other hand, Al-28Si-5Cu-4Mg
alloy showed Al 2 Cu, Al 48 Si 29 Mg 18 and Si. Hot pressing lead to
a signiﬁcant reduction of porosity and partial recrystallization
of spray formed alloys. The room temperature tensile tests of
spray formed hot pressed alloys showed signiﬁcant increase
in ultimate tensile strength compared to as cast alloys. Spray
formed hot pressed Al-28Si-5Cu-4Fe alloy exhibited superior
ultimate tensile strength and signiﬁcant increase in elongation to
fracture. This may be attributed to the presence of homogeneous
distribution of ﬁne Si particles, high content of short needle-like
β-Al 5 FeSi intermetallic and precipitation strengthening phases.

A Comparative Study on Microstructure and Tensile Properties of Spray Formed and Ascast Al-28Si-5Cu-4Fe and Al-28Si-5Cu-4Mg Alloys

In the present investigation, Al-(20-30%wt) Mg2Si-2Cu alloys were synthesized by spray forming process and further processed by hot pressing for densification. The alloys were further subjected to age hardening heat treatment. The spray formed, age hardened and as-cast alloys were characterized by microstructure and mechanical properties. The microstructure of spray formed alloys exhibited finer and evenly distributed primary β-Mg2Si particles and θ-Al2Cu phase and clusters of discrete and high volume fraction of Q-phase. As-cast alloys mainly consist of large sized polygonal primary β-Mg2Si, coarse Chinese script of Al2Cu and needle shaped eutectic Q-phase. Hot pressing of the spray formed alloy promotes the microstructural refinement, reduction in porosity, fragmentation and redistribution of secondary phases. Artificial age hardened alloys exhibits the large quantity of θ-Al2Cu precipitates less than 2 μm size uniformly distributed in the matrix. The β phase re-precipitates in a very fine spherical form results in an increase in the area fraction of β-Mg2Si phase during aging. The significant enhancement in ultimate strength in heat treated and sprays formed alloys as compared to the as-cast alloy. The SEM of fracture surfaces of tensile specimens was taken on spray formed age hardened and as cast alloys. The fractographs revealed the transformation from brittle mode to ductile dimples.

/pdf/microstructure-and-mechanical-properties-of-spray-formed-and-ms9pqkd1zp.pdf

V C Srivastava

Papers

Spray Deposition Process of Hypereutectic Al – Sialloys: An overview

A Comparative Study on Microstructure and Tensile Properties of Spray Formed and Ascast Al-28Si-5Cu-4Fe and Al-28Si-5Cu-4Mg Alloys

Microstructure and Mechanical Properties of Spray Formed and Hot Pressed/HeatTreated Al-(20-30 wt%) Mg2Si-2% Cu Alloy