【導(dǎo)讀】：本文研究和報(bào)道了關(guān)于AZ31B鎂合金商業(yè)片在高溫下的成形行為。第一階段是分析自由脹形實(shí)驗(yàn)，第二階段是分析板材填充封閉模具的能力。變速率敏感指數(shù)。二階段中，在帶有棱形空腔的密閉模具中進(jìn)行成形實(shí)驗(yàn)。同時(shí)分析了相關(guān)的過程參數(shù)對成形。結(jié)果中壁厚填充、最終樣品上圓角半徑及分布的影響。擇適當(dāng)，所研究的商業(yè)鎂板可成形復(fù)雜的幾何形狀。最低的密度，在輕量化上也有很高的潛力，尤其是在移動(dòng)正在使用運(yùn)動(dòng)部件的領(lǐng)域。合金，使得超塑性成形成為一種有吸引力的成形方法。的輕量化部件可以由具有超塑性的單層板通過超塑性成形制造。該氣體可完全替代傳統(tǒng)。目前，BF的原理已被廣泛應(yīng)用到塑料的制造上。在這項(xiàng)工作中，分析了在高溫下通過BF技術(shù)的裝置一塊商業(yè)鎂板的成形行為。過數(shù)字采集的位置傳感器信號(hào)檢測試樣的圓拱高度。整個(gè)試驗(yàn)期間，每個(gè)階段的圓拱高度使用之前的位。置傳感器來測定。圖2顯示了試驗(yàn)試樣，破裂

　　

【正文】 g by the sheet. Fig. 6 Closed die forming tests. a The experimental plan with two pressure levels and two forming time with a central point. b Fillet radius along the square median on the sheet after forming as a function of the forming time for the explored pressure levels In order to quantify the filling, three geometrical parameters have been measured: (i) the contact area between the sheet and the bottom of the die cavity, (ii) the fillet radius on the formed sheet along the median axis and (iii) the fillet radius on the formed sheet along the diagonal of the squared section. Comparing the radius along the median axis and along the diagonal, it can be seen that generally the value along the diagonal axis is larger than the value along the median axis. The difference between these two parameters decreases with forming time: at MPa after 50 s their difference is about 11% and after 2020 s it drops to 4%. In spite of the material was not prepared for superplastic forming purposes, closed die tests has confirmed its great ductility in hot conditions: the sheet after 2020 s at a constant pressure of MPa reaches the smallest fillet radius of about mm (along the median axis of the square) without rupture. Even if the forming time appears to be not cost effective for conventional industrial applications, these results denote a great attitude of this process and of this material in obtaining plex shapes. All the geometrical parameters that have been analyzed put in evidence the non linear relationship between the die filling and the two investigated factors (temperature and pressure): looking at tests performed at MPa the radius variation between 50 and 500 s is much higher than the one that can be measured between 500 and 2020 s (Fig. 6b). Results in the central point denote non linearity between the die filling and the forming pressure: paring the result at MPa it is much more similar to the ones obtained at MPa than to the ones at MPa. Analogous results have been obtained in free bulging tests confirming that the strain rate the sheet is subjected to grow more than linearly with the forming pressure. At constant pressure is well known that, when the sheet contacts the bottom of the die cavity, the mean strain rate in the blank suddenly drops down. In optimized pressure cycles of mon SPF applications, after the contact between sheet and cavity bottom, the pressure bees greater and greater to keep the strain rate around the target value [19]. In constant pressure test, the sheet quickly contacts the bottom of the die cavity, as it can be seen in the test with MPa after 50 s where the sheet has already touched the die bottom, but needs much more time to calibrate and touch die walls (Fig. 6b). In these conditions, the strain rate the sheet undergoes after contacting the cavity bees extremely low even if the higher pressure level is applied Conclusions. The forming behaviour of a mercial AZ31 Mg alloy sheet has been analyzed at elevated temperature both in free bulging and in closed die tests. Results from the experimental activities highlighted that: – even if the material is not pretreated in order to have a superplastic behaviour, it shows large equivalent elongation to failure in the asreceived conditions。 – the biggest elongation to failure can be recorded for the highest temperature and the lowest pressure。 among temperature levels that have been explored, at 460176。C a good promise between elongation to failure, strain rate sensitivity index and material postforming conditions can be achieved。 – decreasing the forming temperature the influence of pressure on the dome height to failure is reduced。 strong non linearities can be found when analyzing the strain rate as a function of pressure, at a constant temperature, or as a function of temperature, at a constant pressure。 – in closed die forming, the material can achieve very small fillet radii, denoting a big ductility at elevated temperature。 – in the examined range of temperature and pressure, the die filling increases more than linearly with pressure and less than linearly with forming time. Further investigations are needed to better understand the effectiveness of forming Mg alloys at elevated temperature with the BF technique. Post forming characteristics, due to microstructural changes and cavitation have to be deeper analyzed. Considering that pressure can be managed during the process to speed up the forming cycle and to optimize thickness distribution along the sheet, the BF process can be considered a good petitor in manufacturing thin walled Mg alloys ponent with plex shapes. Acknowledgements Authors wish to thank the Italian Institution ―Ministero dell’Istruzione, dell’Universit224。 e della Ricerca‖ and ―Fondazione Cassa di Risparmio di Puglia‖ for financing and supporting the present research activity. References 1. Vulcan M, Siegert K, Banabic D (2020) The Influence of Pulsating Strain Rates on the Superplastic Deformation Behaviour of AlAlloy AA5083 Investigated by Means of Cone Test. Mater. Sci. Forum Vols. 447–448:139–144 2. Krajewski PE, Schroth JG (2020) Overview of Quick Plastic Forming Technology. Mater. Sci. Forum Vols. 551–552:3–12 3. Wu X, Liu Y, Hao H (2020) High strain rate superplasticity and microstructure study of a magnesium alloy. Mater. Sci. Forum Vols. 357–359:363–370 4. Jin Q, Wu H (2020) An Experimental Study on Superplastic Behaviors of Magnesium Alloy Sheet. Mater. Sci. Forum Vols. 475–479:2913–2918 5. Watanabe H, Fukusumi M (2020) Mechanical properties and texture of a superplastically deformed AZ31 magnesium alloy. Mater. Sci. Eng., A 477:153–161 6. Blandin JJ (2020) Superplastic Forming of Magnesium Alloys: Production of Microstructures, Superplastic Properties, Cavitation Behaviour. Mater. Sci. Forum Vols. 551–552:211