Abstract
Due to their low density and high specific strength, magnesium alloys offer great potential as a design material for lightweight construction. An economical and energy-efficient method for the production of magnesium wire is the technology of twin-roll casting. In this work, the deformation behaviour of twin-roll cast and heat-treated AZ31 wire pre-profile is investigated for the first time during the compression test at different temperatures (250–400 °C) and forming speeds (0.01–10 s−1). To obtain optimal parameters, a processing map is created, and the microstructural changes during the hot forming processes are determined by accompanying microstructure characterization through an optical microscope and scanning electron microscope. The heat treatment causes a reduction in segregation and a homogeneous microstructure. The average activating energy for plastic deformation of twin-roll cast and heat-treated magnesium alloy AZ31 is 159.008 kJ·mol−1. The instability region of the process map starts at a forming temperature of 250 °C and extends into the range of high forming speeds (1–10 s−1). In this area, cracks in the microstructure can be detected during hot forming. At high temperatures (300–350 °C), dynamic recrystallization at the grain boundaries is observed as the main forming mechanism. Based on these results and observations, existing models for describing the hot forming behaviour of magnesium alloys can be extended and validated.
Highlights
A central approach for solving the global environmental and climate problem is lightweight design
In the present work, the deformation behaviour of an AZ31 wire pre-profile produced at the pilot plant for magnesium twin-roll casting wire of the Institute for Metal Forming (IMF) was investigated for the first time
The central area was embossed with a fine-grained microstructure; a coarser grain appeared in the peripheral area
Summary
A central approach for solving the global environmental and climate problem is lightweight design. The pilot plant to produce twin-roll cast magnesium wire pre-profiles was put into service at the end of 2017. Taacbolre2re.1sM)paoarnteedfiriirnaslgtsmcaanesdlttienMdgealtenhvdoedlt.hsTehnetr7a1n0s◦feCrrheodt through a heated pipe into the headbox to melt is poured through a preheated nozzle into t2h.1e.wTawtienr--RcooollleCdasctlionsged groove (see Figure 1a below). 3T1hieng7o1t0s°iCn whot.%t m[9e]l.t is poured through a preheated nozzle iEnlteomtehnetwater-cooledAcllosed groove (seZenFigure 1a belowM) An t this point, theMmgelt solidifies qAuviecrkalgyewithout any r2e.6lease agent at a tw1.1in-roll casting sp0e.4ed of 4.9 m/min.9T5h.9e oval crosssection of the groove is 20.0 mm × 9.2 mm. Cylindrical speci2m.2e.nHseoatf T5rmeamtmdeniatmanedteCryalnindde1r0Cmommphreesisgiohnt (TFeisgture 1b) were mechanically manufactured from the heat-treated wire pre-profile. These cylindrical compression test specimens were testeTdhseehveearat ltrteimatemsewntitihs tchaerrqieudenocuhtiantg4a6n0d°Cfofromr 1in5gmdiinlaatcocmoredteinr gBÄtoHMRoDseIsLe8t0a5l.D(2019) (com[p1a0n],yinBÄwHhiRch-Tthheertmwoinan-raollylscea)sattwteirme pperera-pturorefsileofis2p50la,c3e0d0,in35a0parnedhe4a0t0ed◦Cinadnudstsrpiaelefdusrnace of 0.0a1n, d0.1ra, p1iadnlyd c1o0osl−e1duinp wtoaatelorg(raoriotmhmtiecmfopremraintugrde)egafrteeerφthoefh0o.4l.dAintgfitrismt,ew. The MTEX MATLAB toolbox was used to analyze the EBSD data [11]
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