Modifications of the Extrusion Process of Magnesium Alloys for Improved Mechanical Properties

2008 ◽  
Vol 367 ◽  
pp. 9-16 ◽  
Author(s):  
Sören Müller ◽  
Klaus Mueller ◽  
Walter Reimers
Keyword(s):  
Mechanical Properties ◽  
Magnesium Alloys ◽  
Differential Effect ◽  
Cold Deformation ◽  
Compressive Loading ◽  
Extrusion Process ◽  
Detailed Knowledge ◽  
Strength Differential Effect ◽  
Strength Differential ◽  
Structural Applications

In the course of the increasing discussions about a reduction of the CO2 emissions magnesium has gained importance since it is the lightest metal for structural applications. Currently magnesium alloys are almost exclusively used as cast parts in the automotive industry because due to their microstructure extruded magnesium profiles exhibit a strong asymmetry in the mechanical properties under tensile and compressive loading (strength differential effect). In order to improve the mechanical properties a detailed knowledge about the influence of the different extrusion parameters on the microstructure of the extrudates is necessary. Therefore, the parameters extrusion method, billet temperature, product speed, extrusion ratio and cooling condition were varied for the extrusion of the magnesium alloys AZ31, AZ61 and AZ80. Subsequently the microstructure was analyzed and the mechanical properties determined. With an additional analysis of the deformation modes of the extruded and cold deformed products it could be discovered that an improvement of the mechanical properties can be achieved by a modification of the extrusion process. Since the strength differential effect in caused by twinning which due to the texture of the extrudates is only active under a compressive loading along the extrusion direction the modification of the extrusion process aims at a suppression of this twinning. Because on the one hand compared to that for dislocation glide the Hall-Petch-Constant for twinning is bigger a grain refinement of the extruded products could be achieved by a predeformation using ECAE similar processes. On the other hand a process has been developed where the profiles are extruded into a hydrostatic counter pressure in order to alter the texture during the extrusion. Thereby the twinning is already activated during the extrusion. Both modifications of the extrusion process result in an increase of the critical resolved shear stress for twinning during the subsequent cold deformation and thus in improved mechanical properties.

Modification in Texture of Magnesium by the Addition of Rare Earth Elements and its Influence on Mechanical Properties

2012 ◽  
Vol 736 ◽  
pp. 307-315 ◽  
Author(s):  
Murugavel Suresh ◽  
Satyam Suwas
Keyword(s):  
Mechanical Properties ◽  
Rare Earth ◽  
Magnesium Alloys ◽  
Aluminium Alloys ◽  
Room Temperature ◽  
Main Obstacle ◽  
Rare Earth Addition ◽  
Structural Applications ◽  
Re Elements ◽  
The Relationship

Mg alloys show limited room temperature formability compared to its lightweight counterpart aluminium alloys, which is a main obstacle in using this metal for most of the structural applications. However, it is known that grain refinement and texture control are the two possibilities for the improvement of formability of magnesium alloys. Amongst the approaches attempted for the texture weakening, additions through of rare-earth (RE) elements have been found most effective. The relationship between the texture and ductility is well established. In this paper, the effect of rare earth addition on texture weakening has been summarized for various magnesium alloys under the two most common modes of deformation methods.

scholarly journals Novel grain refinement of AZ91E magnesium alloy and the effect on hot tearing during solidfication

2021 ◽  
Author(s):  
Abdallah Elsayed
Keyword(s):  
Mechanical Properties ◽  
Grain Size ◽  
Magnesium Alloy ◽  
Grain Refinement ◽  
Magnesium Alloys ◽  
Hot Tearing ◽  
Grain Refining ◽  
Grain Refiner ◽  
Structural Applications ◽  
Hot Tearing Susceptibility

For the A1-5Ti-1B grain refiner, the addition of 0.1 wt.% provided a 68 % reduction in grain size as compared to the unrefined AZ91E alloy at a holding time of five minutes. Grain growth restriction by TiB₂ particles was the source of grain refinement. With the addition of A1-5Ti-1B, only a small reduction in hot tearing susceptibility ws observed because large TiA1₃ particles bonded poorly with the eutectic and blocked feeding channels.The addition of 1.0 wt.% A1-1Ti-3B provided a grain size reduction of 63% as compared to the unrefined AZ91E alloy at a holding time of five minutes. The grain refinement with A1-1Ti-3B addition was attributed to a combination of TiB₂ grain growth restriction and A1B₂ nucleating sites. A significant reduction in hot tearing susceptibility was observed with A1-1Ti-3B addition as a result of a higher cooling rate and shorter local soldification time as compared to the AZ91E alloy. The reduction in hot tearing susceptibility was attributed to the good interface between eutectic and TiB₂ particles. Both grain refiners demonstrated a good resistance to fading during the holding times investigated. In addition, the AZ91E + A1-5Ti-1B and AZ91E + A1-1Ti-3B castings showed much fewer dislocation networks as compared to the untreated AZ91E casting.The development of efficient A1-Ti-B refiners can also improve castability of magnesium alloys. In addition, the fade resistant A1-Ti-B grain refiners can reduce operating costs and maintain productivity on the foundry floor. Thus, magnesium alloy with A1-Ti-B treatment have the potential for more demanding structural applications in the automobile and aerospace industries. Vehicle weight in the aerospace and automotive industries directly impacts carbon emissions and fuel efficiency. An increase in the use of lightweight materials for structural applications will result in lighter vehicles. Low density materials, such as magnesium (1.74 g/cm³) are a potential alternative to aluminium (2.70 g/cm³), to reduce component weight in structural applications.However, current magnesium alloys still do not have adequate mechanical properties and castability to meet the performance specifications of the automotive and aerospace industries. Grain refinement can significantly improve mechanical properties and reduce hot tearing during permanent mould casting. Recently, Al-Ti-B based grain refiners have shown potential in grain refining magnesium-aluminum alloys such as AZ91E. This study investigates the grain refining efficiency and fading of A1-5Ti-1B and A1-1Ti-3B in AZ91E magnesium alloy and their subsequent effect on hot tearing.The grain refiners were added at 0.1, 0.2, 0.5 and 1.0 wt.% levels. For the grain refinement and fading experiments, the castings were prepared using graphite moulds with holding times of 5, 10 and 20 minutes. For the hot tearing experiments, castings were produced representing the optimal addition level of each grain refiner. The castings were prepared using a permanent mould with pouring and mould temperatures of 720 and 180 ºC, respectively. The castings were characterized using SEM, TEM, optical microscopy and thermal analysis.

scholarly journals Strength differential effect in age hardened aluminum alloys

2017 ◽  
Vol 99 ◽  
pp. 144-161 ◽  
Author(s):  
Jens Kristian Holmen ◽  
Bjørn Håkon Frodal ◽  
Odd Sture Hopperstad ◽  
Tore Børvik
Keyword(s):  
Aluminum Alloys ◽  
Differential Effect ◽  
Strength Differential Effect ◽  
Strength Differential

scholarly journals Cold-Sprayed Aluminum-Silica Composite Coatings Enhance Antiwear/Anticorrosion Performances of AZ31 Magnesium Alloy

2018 ◽  
Vol 2018 ◽  
pp. 1-8
Author(s):  
Lijia Fang ◽  
Yuting Xu ◽  
Li Gao ◽  
Xinkun Suo ◽  
Jianguo Gong ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Surface Modification ◽  
Magnesium Alloys ◽  
Cold Spray ◽  
Protective Coatings ◽  
Composite Coatings ◽  
Silica Content ◽  
Protective Layers ◽  
Structural Applications ◽  
Enhanced Surface

Extensive efforts devoted in recent years to booming structural applications of lightweight magnesium alloys are usually undermined by their insufficient surface properties. Surface modification is therefore necessarily required in most cases for enhanced surface integrity of the alloys. Here, we report construction of aluminum-silica protective layers by cold spray on AZ31 magnesium alloys, and the effect of the silica additives on microstructure and mechanical properties of the coatings was examined. The ceramic particles were dispersed evenly in the coatings, and increased silica content gives rise to enhanced adhesion, antiwear performances, and microhardness of the coatings. The even distribution of silica in the coatings altered the wear regimes from adhesive to abrasive wear. The cold spray fabrication of the aluminum-silica protective coatings would facilitate structural applications of the magnesium alloys.

Sign in / Sign up

Export Citation Format

Share Document