Lightweight construction material with dense, pore-free structure, comprises magnesium silicide reinforcing material in aluminum matrix and is obtained by squeeze-casting

摘要

#CMT# #/CMT# Production of a material (A) comprising an aluminum-based matrix in which magnesium silicide-containing reinforcing material is embedded, the magnesium silicide content of (A) being 8-30 wt. %, involves melting, squeeze-casting and solidifying a mixture (B) containing aluminum, silicon, magnesium and optionally other metal(s). #CMT# : #/CMT# An independent claim is included for the material (A) obtained by the process. #CMT#USE : #/CMT# (A) is a lightweight construction material, shapable by hot-working, rolling, extrusion and forging. #CMT#ADVANTAGE : #/CMT# (A) has a dense, pore-free structure, and is thus useful in a wide range of applications. (A) is not subject to thermal cracking, and can be hot-worked without cracking at conventional shaping temperatures (specifically to degrees of deformation of up to 1.25, dependent on composition). (A) also has a very low density (specifically less than 2.7 g/cm 3>; claimed); is recyclable (by remelting) without deterioration of properties; and shows good mechanical properties (specifically good extension at break, tensile strength and workability). #CMT#METALLURGY : #/CMT# Preferred Process: The mixture (B) contains (by weight) 5-24% silicon, 8-30% magnesium, optionally up to 5% other metals(s) and aluminum to 100%, the components being added in the form of pure elements or preliminary alloys. The additional metallic component specifically consists of 0.2-1.0% copper, manganese and/or zinc and/or 0.05-0.3% cerium mischmetal and/or calcium. Casting is carried out at a temperature which is above 700[deg] C and at least 50[deg] C higher than the liquidus temperature of the mixture (B). The melt is subjected to vibration treatment (preferably at a frequency of 20-100 Hz) during solidification. The melt is purged and blanketed with argon. The obtained material (A) is heat treated, specifically by solution annealing for less than 1 hour at more than 500[deg] C, followed by quenching and holding for more than 2 hours at 160[deg] C or more. Preferred Product: The matrix contains embedded magnesium silicide particles. The density of (A) is less than 2.7 (preferably 2.3-2,6, especially 2.45-2.6) g/cm 3>. #CMT#EXAMPLE : #/CMT# A molten mixture of (by weight) 8.2% magnesium, 4.7% silicon and aluminum to 100% was squeeze-cast and solidified to give a material (A') of density 2.59 g/cm 3>. The structure was highly dense and completely free of casting faults. The mechanical properties of (A') were as follows: (i) in the cast state (F state) Rp 0.2 101 MPa, Rm 201 MPa and A 6.3%; (ii) in heat treated form (T6 state) Rp 0.2 304 MPa, Rm 323.5 MPa and A 2%; and (iii) in extruded and heat treated form (extruded + T6 state) Rp 0.2 233 MPa, Rm 280 MPa and A 9.8%. (A') thus showed excellent mechanical properties in the cast and post-treated states, while showing lower density than conventional cast materials.