Improvement of Mechanical Properties of Semi-Solid Alloys by ECAP Processing

Abstract

Recently, semi-solid processing is paid to attention in the field of the light alloys. By this method, it is improved ductility and fatigue strength. Although, because of those mechanical properties of the elongation and toughness is not excellent, the range that can be the application to parts is limited. On the other hand, it is reported that grain refinements cause improvement of ductility and appearance of super plasticity. Then, Equal-Channel Angular Pressing (ECAP) method is reported to be effective to the sample making of a bulk and ultra fine grain in various alloys in recent years. In this study, it tried to improve ductility and durability due to making ultra fine grain in AC4CH alloys by the ECAP method, and the influence of ECAP processing on the mechanical property of AC4CH was investigated. As the result, the ductility of AC4CH has improved by ECAP processing. However, the tensile strength of AC4CH declined along with the increase in the number of passes. So, for the purpose of additional improvement of tensile strength, ECAP-Back Pressure (ECAP-BP) method that was reported to be more effective for grain refinements than ECAP method was applied to semi-solid AC4CH and compared with ECAP method. As the result, the tensile strength of AC4CH was maintained by use of ECAP-BP. Moreover, both ductility and toughness of that have been also improved.

Development of the continuous process method for ECAP using a tri-axis rotary die and microstructural evolution of semi-solid aluminium alloy

“…We have plotted additionally the evaluation result of a sample processed at 473K using the other conventional die (φ=90°, ψ=15°) reported in ref. [11] in fig. 5.…”

“…Particularly, the size of ψ is the parameter regarding the processing strain as is obvious from equation (1), and many researches have been investigated the effect of it on ECAP processing workpiece. There are past findings that deformation behavior is less related it if ψ is lower than 20° [12,13]; this can be explained by investigations that the dependence of strain distribution on ψ is decreased with a higher work hardening material [14] and that an apparent angle of ψ becomes 22° on a quasi-perfect 90°, ψ15° [11] Continuous ECAP at 573K Conventional ECAP at 573K Conventional ECAP at 473K Conventional ECAP at 473K Figure 5: Influence of ECAP process on impact properties. Material toughness is improved by ECAP without depending on processing method, processing temperature, and configuration of die corner.…”

Improvement in toughness of semi-solid light metal by the ECAP process

“…Flemings [1] of MIT began research on casting in the semi-solid state for the reduction of solidification shrinkage, compositional segregation, and cavities in the early 1970s. It was observed in our papers [2,3] that semi-solid casting, i.e., the homogenization of heating distribution by means of a stirring operation and high cooling rate, provides a reduction in micropores, spheroidizing of the primary phase, and grain refinement. Several investigations have been conducted on semisolid casting using both aluminum cast and wrought alloys.…”

The Microstructural Refinement of the A356 Alloy Using Semi-Solid and Severe Plastic-Deformation Processing

“…A few limited studies have applied the combination of semi-solid and ECAP processes to improve the mechanical properties [17,18]. Subjecting the A356 alloy to heat treatment (annealing) together with ECAP results in the improved hardness and wear-resistance of the alloy [19]. The aim of this study was to achieve the following objectives: First, investigate the microstructural refinement of the A356 alloy using a semi-solid process before and after T6 heat treatment.…”