IMPROVING THE DUCTILITY PROPERTIES OF HARD-TO-DEFORM HYPEREUTECTOID SILUMIN ALLOYS BY HELICAL ROLLING

摘要

Of the many structural aluminum alloys used in different areas of machine-building, Al-Si alloys having a silicon content considerably higher than the eutectic composition have recently been receiving special attention. These alloys generally contain 18-25 percent Si and several alloying elements (Cu, Ni, Ti, Zn, etc.). Hypereutectoid silumins can be regarded as natural composite materials having a two-phase structure composed of ductile eutectic, brittle silicon crystals, and phases of the systems Al-Fe and Al-Ti with sizes of < 100 mu m. The two-phase structure Of Such silumins gives them a unique range of physical and mechanical properties (Table 1). Their low coefficient if linear expansion, high corrosion resistance, excellent weldability, and high elastic modulus make them interesting as mateals for piston assemblies (pistons and sleeves) and brake pairs in automobile and aircraft construction and for oil and gas nines that are subject to large temperature gradients and aggressive media.