Effect of Process Parameters on Distortion and Residual Stress of High-Pressure Die-Cast AZ91D Components

Abstract

This paper presents a study of distortion and residual stress within a high-pressure die-cast AZ91D component, cast under different processing conditions. The influence of process parameters, i.e., die temperature, cooling time, intensification pressure and first-phase injection speeds, was examined. Distortions were measured using the inhouse standard analog quality control fixture. Residual stress depth profiles were measured using a prism holedrilling method. It was found that the most important process parameter affecting the distortion was intensification pressure and the second most important was temperature difference between the two die halves (fixed and moving side). Tensile residual stresses were found very near the surface. Increasing the intensification pressure resulted in an increased level of tensile residual stresses.

Effect of Process Parameters on Distortion and Residual Stress in High-Pressure Die Cast AZ91D Components After Clean Blasting and Painting

“…It should be mentioned that the distortion and residual stress values at the as-cast state were reported earlier. 9…”

“…Figures 5 and 6 show the SVM stresses profiles for all conditions evaluated at points R1 and R2. The residual stress data at an as-cast state were provided from previous work 9 as a baseline for the changes incurred by the subsequent post-processing. To quantitatively describe residual stresses, different characteristic measures of the residual stress were reported: r rs s , the residual stress at the surface (MPa.…”

“…7 Besides, there is a possibility that at high temperatures, residual stress may relax, resulting in part distortion. 8 In the recent work by the authors, 9 the effect of HPDC process parameters on both distortion and residual stress response of an AZ91D component was studied. It was understood that the application of intensification pressure significantly reduced the component's distortion, but significantly increased the residual stress near the surface.…”

“…However, increasing the moving side temperature decreased the residual stress near the surface, suggesting that stress relaxation may take place. 9 It has been well established that the state of the surface roughness obtained at the final stage of the cast component has a great effect on fatigue strength. This knowledge is vital as-clean blasting (using cut wire grit) is a common form of surface conditioning before painting and has strong similarities to shot peening resulting in significant compressive stress generation.…”

“…This study was made as a continuation of a previous study on the influence of HPDC processing parameters in the as-cast state on the distortion, and residual responses were of the main interest. 9 The current study focuses on four different HPDC process parameters found relevant (a) first phase injection speed, (b) the temperature difference between the two die halves through variation of the temperature of fixed half of the die, (c) cooling time, and (d) intensification pressure. The most crucial understanding to generate was to understand how the HPDC processing parameters can be traced through the post-processing sequence as residual stress and distortion.…”