High-pressure sliding using rod samples for grain refinement

Abstract

High-pressure sliding (HPS) is a process of severe plastic deformation (SPD) for significant grain refinement and it is similar to high-pressure torsion (HPT) as both processes are operated under high pressure. Whereas the HPT process uses disk or ring samples, the HPS process is applicable to rectangular sheet samples. In this study, it is demonstrated that the HPS process is also applicable to rod samples. To achieve a homogeneous microstructure throughout the cross section of the rod, the sample is rotated along the longitudinal axis after each processing. The HPS process is carried out on pure Al, Al alloys (Al-3%Mg-0.2%Sc, A2024 and A7075) and a Mg alloy (AZ61) under a pressure in the range of 1-2 GPa. It is shown that a homogeneous microstructure is developed in all samples through rotation along the longitudinal axis by 60 degrees after each processing. The Al alloys and the Mg alloy exhibit grain sizes well less than 500 nm and superplastic elongation well more than 400% for the A2024 and A7075 alloys and well more than 1000% for the Al-3%Mg-0.2%Sc alloy and the AZ61 alloy. It is thus antgicipated that the HPS process provides good potential for scaling-up the sample size through not only sheets but also rods.

Extra Strengthening and Superplasticity of Ultrafine-Grained A2024 Alloy Produced by High-Pressure Sliding

“…The intense shear strain introduced in the samples results in ultra ne grains. One advantage of the HPS process is that it can be applied to samples with practical shapes such as sheets and rods; so far, it has been applied to sheets of pure Al (99.99%), Al-Mg alloy, AZ61 Mg alloy, and 7000 series Al alloy [18][19][20] , as well as rods of pure Al (99.99%), Al-Mg alloy, AZ61 Mg alloy, 2000 series Al alloy, and 7000 series Al alloy [21][22][23] . The ca-pacity of the HPS machine was recently increased to 500 tons 24,25) , which allows the samples to be scaled up 24,25) .…”

Scaling up of High-Pressure Sliding (HPS) for Grain Refinement and Superplasticity

“…[32,33] However, the direct application to sheet or rod samples should be feasible when sliding under high pressure, called high-pressure sliding (HPS), is used as schematically illustrated in Figure 1. [34] This process was developed such that two samples of sheets [34] or rods [35] were placed between the anvils and plunger. The plunger was then pushed for shearing while applying a load on the samples between the anvils.…”

高圧スライド法を用いたTi同素変態のその場放射光X線解析

“…(HPS: High-Pressure Sliding) 加工 55) と呼ばれ，粉末の固化 60) をはじめ，多くの金属材料 [56][57][58][59] に利用されている．この HPS プロセスは棒状試料 [61][62][63][64] やパイプ状試料 65) にも適用可能であ ることが示されている．さらに，試料の逐次送りと組み合わ V i e w せることで，SPD 処理面積が拡大できることも示されてい る 66,67) ．このような開発は，SPD プロセスの実用化を目指し たもので，最近のレビュー論文 68) でも詳しく解説されてい る．本研究では，HPS プロセス装置はむしろ小型にして，シ ンクロトロン光施設における高圧高温下でのその場 X 線解析 に使用する． HPT や HPS プロセスによる特性向上は，プロセス中に発 生する高密度の格子欠陥に起因している [69][70][71] ．このような格 [72][73][74] やマルチアンビル装置 75,76) を用いて行われ ることが多い．これらは主に静水圧条件下で使用されるが， DAC の場合，Bridgman のアイデアに沿って，一方のダイヤ モンドアンビルを他方に対して回転させることで意図的に塑 性変形を導入できる 13) ．Blank らは DAC を用いてせん断ひず みを導入した最初であり 77,78) ，Levitas らは DAC でひずみ導 A d v a n c e…”