Papers by Author: Xin Sheng Huang

Abstract: A new ECAP process method called rotary-die ECAP (RD-ECAP) was developed to form fine-grained bulk materials such as aluminium alloys, magnesium alloys, aluminium composites, and titanium, all of which can be processed under conditions of 573-773K, at an approximately 0.9-2.4 mm/s punch speed of 300MPa or lower. By the RD-ECAP method, ECAP processing of up to 2 passes can be done without sample removal and samples processed over 30 cycles were obtained.

Abstract: The AZ61 magnesium alloy was subjected to the differential speed rolling at different rolling conditions including reduction per pass, rotation speed ratio and rolling temperature, and the influences of the rolling conditions on microstructure, texture, mechanical properties and formability of the as-rolled sheets were investigated. Increasing the reduction per pass results in a more homogeneous microstructure and a relatively weaker basal texture. With increasing the rotation speed ratio, the inclination angle of basal pole toward the rolling direction increases and the stretch formability enhances correspondingly. Increasing the rolling temperature has an effect on weakening the basal texture intensity and leads to the enhancement of stretch formability.

Abstract: It was reported that the cold and warm press formability of the magnesium alloy was improved by the application of a differential speed rolling (DSR). However, it can be considered that the microstructure and the texture of the DSR processed sheets greatly change with the rolling conditions. In this study, commercial AZ31B magnesium alloy extrusions were processed by DSR at a differential speed ratio of 1.167 and a reduction per pass of 10% or less, and the effects of the rolling temperature, the number of rolling passes and reversal of the rolling direction on texture and mechanical properties were examined. As a result, it was found that the optimal rolling temperature in terms of the workability and formability of the material was 573 K. And the elongation and formability were maximal in sheets processed by 4–6 passes of DSR. Moreover, reversing the shear direction made the microstructure more homogeneous and finer than unidirectional shear, and improved the mechanical properties and formability. This improvement was greater in samples where the shear direction was reversed once in the middle than where it was reversed for each pass.

Abstract: The mechanical properties of the AZ31B alloy sheets processed by differential speed rolling (DSR) from the cast ingots homogenized at two different conditions were investigated. There still existed the uneven distribution of Al and Zn in the ingot homogenized at 673 K for 6 h, while it was homogeneous for the ingot homogenized at 723 K for 24 h. Compare with the sheet rolled from the ingot homogenized at 673 K for 6 h, the sheet rolled from the ingot homogenized at 723 K for 24 h exhibited a lower proof stress, a larger elongation, and a lager strain hardening exponent. The improvement in the ductility can be attributed to the elimination of the microsegregation of Al and Zn in the matrix.

Abstract: Possibilities of the consolidation process using hot extrusion and subsequent hot rolling were investigated in order to recycle the cutting chips of the aluminum alloy efficiently. For the rolling process, differential speed rolling (DSR) was also applied in addition to normal rolling. Several kinds of cutting chips with different size and cleanliness were collected through turning 6061 aluminum alloy round bars. From these cutting chips, recycled material sheets were produced under various processing conditions via hot extrusion and subsequent hot rolling. Non-recycled material sheets were also prepared for comparison. All samples were characterized by optical microscopy, SEM(EBSP), X-ray texture analysis, tensile test and corrosion test. As a result, it was found that the recycled material sheets produced under optimum processing conditions had smaller grain sizes than those of the non-recycled ones, therefore the mechanical properties and the corrosion resistance of the recycled material sheets were almost comparable to those of the non-recycled ones. Moreover, concerning the DSR processed sheets, the traces of the chip interface, which were clearly observed in the normally rolled ones, almost disappeared, and the appearances were remarkably improved. Then the DSR processed sheets significantly surpassed the non-recycled ones in the tensile properties and the corrosion resistance.

Abstract: Noncombustible Mg-8Al-2Ca rods were processed by RD-ECAP. The magnesium alloy rod had Mg matrix and Al2Ca second phase. Grains with about 20 μm in diameter were observed in the matrix of the raw materials. The grains in matrix had no anisotropy. On the other hand, positions of second phase particles had anisotropy and the second phase particles formed lines. The samples processed by RD-ECAP had no crack and the samples had 20mm diameter. Grains in matrix of the 4 pass RD-ECAP sample had no anisotropy and the grains had under about 5 μm in diameter. The second phase particles had round shapes and were uniformly distributed as compared with the raw material rod. Therefore, the RD-ECAP is useful for forming noncombustible Mg-8Al-2Ca alloy with fine-grains.

Abstract: An AZ31 (Mg-3Al-1Zn-0.35Mn in mass%) alloy sheet exhibiting the inclination of the basal plane from the rolling plane at about 15º, was fabricated by a DSR processing with a roll speed ratio of 1.167. Compared with the normal rolled sheets, the DSR processed sheets showed a lower 0.2% proof stress, a larger elongation, a smaller r-value and a larger n-value. The Erichsen value at room temperature significantly increased from 2.2 to 3.1, and the deep drawability also improved.

Abstract: A DSR processing with a roll speed ratio of 1.08 was carried out on an AZ31 alloys with Mn additions of 0, 0.2, 0.4 and 0.6 wt.% for investigating the effects of Mn on the microstructural evolution and mechanical properties. The amount of the Al-Mn compounds increased with increasing the Mn content. Compare with the DSR processed sheet without Mn addition with a homogeneous grain size, those with Mn additions exhibited an inhomogeneous microstructure due to the appearance of the shear bands comprising the small grains around 5 μm. The Mn addition exhibited a significant effect in grain refinement even for a low content of 0.2 wt.%, which reduced the average grain size from about 25 μm to 10 μm. The Mn addition resulted in the significant increases in the tensile strength and the 0.2% proof stress by about 25 MPa and 40 MPa, respectively.

Abstract: A differential speed rolling (DSR) processing with a roll speed ratio of 1.167 was carried out on an AZ31 alloy for investigating the effects of DSR on microstructure, texture and mechanical properties. The DSR processed sheet showed unidirectional shear bands with a small grain size of 5.5 μm inclining to the rolling direction, and the basal plane tended to incline at about 15º from the rolling plane toward the rolling direction. Compared with the normal rolled sheet, the DSR processed sheets showed a lower proof stress and a larger elongation with an increase from 21% to 26% in the rolling direction. The proof stress increased and the elongation decreased with the angle between the tensile direction and the rolling direction.