Commercial Production of High-Technology Alloy V-1341 of the Al – Mg – Si System with Calcium Addition

Abstract

Production of ingots and commercial-size sheets from an Al -Mg -Si-base alloy V-1341 with calcium addition is described. Their structure, phase composition and mechanical properties are studied. It is shown that calcium enters primarily phases Al x Si y Ca and Al x Si y Mg z Ca of variable composition. INTRODUCTIONThe interest in alloys of the Al -Mg -Si system in aircraft engineering and machine building is growing from year to year due to the combination of strength and corrosion properties, high process ductility and good weldability [1].A new promising medium-strength aluminum alloy V-1341 of the Al -Mg -Si system with an additive of 0.05 -0.15% Ca has been designed for the production of complex-shape articles with enhanced air-tightness for the aircraft and automotive industries from cold-deformed sheets [2]. The alloy was supposed to be an alternative to Al -Mg alloys with a lower strength, which are not vacuum-tight at a less than 2-mm thickness of the sheets in welded units operating under pressure [3] and are susceptible to formation of strain bands under cold tensile deformation. It has been shown that sheets from alloy V-1341 are well adaptable to cold forming due to their fine-grained structure and uniform distribution of the orientations of grains [4].The positive effect of calcium on the structure, mechanical properties, adaptability to manufacture and weldability of some aluminum alloys has been shown in [5 -8]. The mechanism of its action is determined by the alloying system, is quite complex and not quite understandable, which requires further study [9]. In the recent years a calcium additive has been introduced not only into aluminum alloys, both deformable and castable [10,11], but also into magnesium alloys [12 -14].The aim of the present work was to study the effect the addition of calcium on the structure and properties of alloy V-1341 used for commercial production of ingots and sheets. METHODS OF STUDYWe studied ingots with cross section 300´1100 mm from alloy V-1341 with different calcium contents (0.03 wt.% Ca in alloy 1 and 0.12 wt.% Ca in alloy 2 ) and from alloy AV (alloy 3 ) of the same system without calcium [15,16]. The ingots were cast by the semi-continuous method into a sliding mold; in all the cases bars from Al -5% Ti -1% B were introduced into the feed pan.The ingots were annealed at 380 -420°C for 2 h and used to make test pieces for differential thermal analysis. The results of the analysis were used to choose the temperature for homogenizing the ingots. Transverse templates were cut from the homogenized ingots to study the zonal segregation, the microstructure, and the mechanical properties.Alloy 2 was used to make sheets with a thickness of from 0.8 to 3 mm by hot and cold rolling. The sheets were quenched in water after heating at 525°C in a saltpeter bath with a hold of from 10 to 40 min and then subjected to artificial aging. Metallographic analysis of the ingots and of the sheets was performed with the help of a light microscope in polarized light using laps after col...