Mechanical testing of titanium/aluminium–silicon interfaces by push-out

Abstract

Abstract:Mechanical properties of Ti/Al-7Si assemblies produced by insert moulding have been studied with a classical push-out test and a variant that is the circular bending test. Special care has been taken for controlling both the reactivity at theTi/Al-7Si interface and the metallurgical health of the Al-7Si matrix. Mechanical tests until complete debonding have been completed with interrupted tests, metallographic characterizations and FEM analysis of elastic stress state. A mean shear strength of the interface of about 120 MPa has been obtained. When the Ti insert is solely fretted in the matrix, without chemical interaction between Ti and the Al-7Si alloy, the mean shear strength is significantly lower (48 MPa). This result clearly shows that chemical interaction at the interface (formation of a thin TiSi layer at the Ti side and a thick Al 3 Ti(Si) layer at the Al-7Si alloy side) improves the mechanical properties of the assembly. It is also shown that the failure sequence is characterized both by crack propagation from bottom to top and matrix yielding from top to bottom. Actually, interface damaging begins by crack initiation at the specimen bottom face (not at the top face, under the indenter) in a nearly pure mode I solicitation at a radial tensile stress of about 100 MPa.

Interfacial microstructure and mechanical properties of Ti−6Al−4V/Al7050 joints fabricated using the insert molding method

“…However, at 770°C, a thick interface with many shrinkage voids was observed. These voids were reported to exert detrimental effects on the mechanical characteristics of bimetallic joints [13]. Thus, the interfacial morphologies of Ti−6Al−4V/Al7050 joints strongly depended on the holding temperature in the first stage, and good interfacial metallurgical bonding can be possibly attained by parameter optimization, as shown in Fig.…”

“…Interface shear strength was measured using classical push-out tests, as described in Ref [13]. A universal testing machine was used to conduct push-out tests.…”

“…A universal testing machine was used to conduct push-out tests. Interfacial shear strength (τ) can be calculated using the following equation [13,15]:…”

Mechanical testing of titanium/aluminium–silicon interface: Effect of T6 heat treatment

“…It was recently demonstrated that an insert moulding of a titanium (Ti) rod in an Al-7Si-0.3Mg (in wt%) aluminium alloy can, when processed under appropriate conditions, lead to the formation of a strong metallurgical bond at the insert/alloy interface [1]. More precisely, a chemical reaction proceeds between the liquid aluminium alloy and the solid titanium insert, giving rise to the formation of a thin (less than 10 m thick) and continuous interface reaction layer.…”

“…More precisely, a chemical reaction proceeds between the liquid aluminium alloy and the solid titanium insert, giving rise to the formation of a thin (less than 10 m thick) and continuous interface reaction layer. The mechanical properties of the resulting Ti/Al-7Si-0.3Mg joints, as evaluated by tensile testing [9] or pushout testing [1], have been shown to be higher than those of similar joints formed between cast iron inserts and an Al-7Si-0.3Mg alloy [9], or between mild steel inserts and an Al-13Si alloy [7]. Furthermore, it is well known that the mechanical properties of the magnesium-containing aluminium-silicon alloys can be enhanced by a heat treatment, of which the most widely used is the T6 treatment, made up of a solution treatment at 520-550 • C followed by quenching and artificial ageing [10].…”