Spark plasma sintering and hot compression behaviour of AZ91 Mg alloy

Abstract

In the present investigation, the microstructural characterisation of the AZ91 Mg alloy produced by spark plasma sintering (SPS), as well as the evaluation of its hot compression behaviour, has been performed. Based on the differential scanning calorimetry analyses of the starting powders, three SPS cycles are investigated, using temperatures of 400 and 450°C, and at 450°C with previous solubilisation soaking at 420°C. Despite different microstructural and hardness characteristics, the three alloys display similar hot compression behaviour. At 200°C, the formation of an unstable crack, which propagates at 45° with respect to the loading axis, is observed after the occurrence of the peak load. At higher testing temperatures, after reaching the peak stress, the flow stress decreases slowly with increased strain of ∼0·51. Such behaviour corresponds with the observation of an accelerated cracking due to the propagation of decohesions at the interparticle regions. Ultimately, SPS allowed for attainment of high relative density; however, the sintering degree of the materials was quite low.

Effect of Short Attritor-Milling of Magnesium Alloy Powder Prior to Spark Plasma Sintering

“…UCS of ~380 MPa was achieved regardless of the sintering temperature. As mentioned in the Introduction, poor deformability of samples sintered from the gas-atomized magnesium has been reported in several studies and was directly associated with the MgO layer present along the former powder boundaries [ 7 , 8 , 10 , 11 ]. Concerning the powder metallurgy technique, a decrease in the ductility is often associated with the residual porosity and coalescence of pores and microcracks during the loading [ 29 ].…”

“…Consequently, 3D net-like MgO phase distribution is usually present in consolidated samples along the former powder particles’ boundaries [ 7 , 8 , 9 ]. It was shown in several studies that such distribution of MgO has a negative effect on the ductility of bulk samples [ 7 , 8 , 10 , 11 ].…”

Microstructure and Mechanical Properties of Spark Plasma Sintered Mg-Zn-Ca-Pr Alloy

“…SPS allows fast densification at lower temperature in contrast to conventional sintering techniques, resulting in the retention of nanocrystalline structures and non-equilibrium alloys produced by HEMA, and associated properties [34,35]. SPS is advantageous for sintering metallic powders due to its ability to produce a sample with an ultra-fine microstructure without defects and pores [36,37]. This process also helps in retaining the refined grain size, which is obtained after significant refinement through milling [38].…”

Sıcak Presleme Yöntemi ile AZ91 Magnezyum Alaşımının Üretimi

“…Toz metalürjisi yöntemleri ile üretilebilen küçük taneli yapı daha iyi dayanım değerleri sağlarken, ikincil işlemlere olan gereksinimin çok az ya da hiç olmaması ve üretim için daha düşük sıcaklıklara ihtiyaç duyulması daha düşük maliyet avantajını beraberinde getirmektedir. Literatürde AZ91 alaşımlarının toz metalurjisi ile üretilmelerini konu edinen son derece sınırlı sayıda yayın bulunmaktadır [10][11][12][13]. AZ91 matrisli kompozitlerin üretilmesinde ise dökümde karşılaşılan sorunlar yüzünden toz metalurjisi yöntemlerinin sıklıkla kullanıldığı görülmektedir [14][15][16][17][18].…”