Effect of rapid solidification and calcium additions on Sn-38 wt.%Pb-6 wt.%Sb melt-spun alloys

The effect of calcium additions on the structure and physical properties of melt-spun process Sn-38Pb-6Sb alloys have been experimentally investigated at a solidification rate of ~105 K/s. Structure, internal friction, elastic moduli, microhardness and electrical resistivity of the Sn-38%Pb , Sn-38%Pb -6%Sb , Sn-38%Pb -6%Sb-0.5%Ca , Sn-38%Pb -6%Sb -1%Ca , Sn-38%Pb -6%Sb -1.5%Ca , Sn-38%Pb -6%Sb -2%Ca , Sn-38%Pb -6%Sb -2.5%Ca (in wt%) rapidly solidified alloys are investigated. The results showed that the mechanical and electrical properties values are enhanced for ternary Sn-38%Pb -6%Sb alloy. The examined mechanical and electrical conductivity decreased by addition of calcium content in the studied alloys. It also leads to with increasing Ca content the SnSb inter-metallic compound (IMC) precipitates are increased in the Sn matrix. The results were explained in terms of the dislocation theory, effect of quenching rate on the produced density fluctuations in composition and the modes of interaction of crystal lattice defects.

Diffusion Kinetics in Explosive Cladding of Dissimilar Alloys as Described through the Miedema Model/ Kinetyka Procesu Dyfuzji W Układach Platerów Wytwarzanych Z Wykorzystaniem Energii Wybuchu, Na Bazie Stopów O Silnie Odmiennych Właściwościach, Opisanych Modelem Miedema

Explosive cladding of dissimilar plates is achieved by the intensive deformation occurring at high pressure and temperature generated from the detonating explosive at the collision interface. The interface morphology, with its characteristic undulations, is dictated by the extent of kinetic energy spent at the mating interface. Nevertheless, the inter-metallic compound formation at the mating interface weakens the joint. The prediction of the probability of inter-metallic formation at aluminum-SS 304, copper-SS 304 and titanium-SS 304 explosive cladding interfaces is attempted in this study by employing Miedema model. Granular explosives (detonation velocity: 4000 m/s) and parallel plate combination were employed with uni-loading ratio (standoff distance-5 mm). The influence of chemical energy in determining the bond strength of explosive clads is discussed as well.

Structure and Properties of Zn-Ti0.2-Cu0.15 Single Crystal Containing Eutectic Precipitates

Some structure observations for the Zn-Ti0.2-Cu0.15 single crystal obtained by the Bridgman method are presented. The structure contains (Zn) - phase with inclusions of Zn16Ti inter-metallic compound. The Zn16Ti intermetallic compound is localized within the eutectic precipitates. A morphology of the Zn16Ti compound varies according to the solidification condition imposed during the single crystal growth. The block, great size particles are a characteristic element for the alloy which composition is situated nearly the eutectic point in the phase diagram. These particles were not observed previously in the hypoeutectic Zn-Ti alloys. Mechanical properties of the obtained single crystals are also investigated. Critical resolved shear stress (CRSS) during deformation in a basal slip system (0001)<11-20>is determined. The changes of the CRSS for the Zn-Ti0.2-Cu0.15 single crystals within the range of temperatures from 200K to 370K are presented. The obtained data are compared with previously investigated results for the (Zn) single crystals containing lower (hypoeutectic) titanium addition

Nanoindentation of Porous Die Attach Materials as a Means of Determining Mechanical Attributes

A die attach nanopaste for high temperature use on silicon carbide (SiC) based power semiconductor devices was developed utilizing silver (Ag) and aluminium (Al) nanoparticles as well as organic additives. Total nanoparticle content was varied at 84.7, 85.5, 86.2 and 87 wt%, while the Ag to Al ratio was fixed to 80:20. The die attach nanopaste was sintered in open air at 380 °C for 30 minutes to create an Ag-Al inter-metallic compound between the SiC die and substrate. To determine the mechanical attributes of the post-sintered die attach interlayer, nanoindentation was performed on the samples. It was found that, a low Young modulus of elasticity, E, between 9.3-9.8 GPa was obtained. This was followed by a reduction in hardness as well as stiffness for the post-sintered Ag80-Al20 die attach material when compared against that of solder alloys or bulk metals. The formation of pores in the die attach material as it underwent sintering is believed to have contributed to this decrease in mechanical properties. The findings of this research enables the possibility of introducing a much cheaper die attach material for high temperature devices, which also has excellent mechanical properties to alleviate thermal mismatch issues between the semiconductor die and substrate.