Microstructural evolution and mechanical properties of multi-directionally forged Si P /ZA22 composite
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(2020) 20:118
ORIGINAL ARTICLE
Microstructural evolution and mechanical properties of multi‑directionally forged SiP/ZA22 composite D. Yousefi1 · R. Taghiabadi1 · M. H. Shaeri1 · I. Ansarian1 Received: 11 May 2020 / Revised: 31 August 2020 / Accepted: 18 September 2020 © Wroclaw University of Science and Technology 2020
Abstract The effect of multi-pass multi-directional forging (MDF) on the microstructure and mechanical properties of Zn–22Al– xSi (X = 4 and 8 wt. %) alloy, also known as SiP/ZA22 composite, was investigated. MDF process was applied at 100 °C for one, three, and five passes with the strain of 0.47 per pass. According to the results, MDF refined and homogenized the composites microstructure so that the average size of primary Si ( SiP) particles reduced from 25.0 µm and 30.4 µm in as-cast ZA22-4Si and ZA22-8Si composites to about 6.2 µm and 7.3 µm in five-pass MDFed condition, respectively, and their distribution shifted to the smaller size range. Mechanical properties tests revealed that multi-pass MDF has softened the investigated composite. For instance, the hardness, tensile strength, and shear strength of ZA22-4Si composite reduced from 83 HV, 280 MPa, and 165 MPa in as-cast condition to about 58 HV, 160 MPa, and 118 MPa in the five-pass MDFed sample, respectively. This is while its fracture strain increased from 15% to about 40% with the strain rate of 1.2 × 10–3 s−1. Keywords Multi directional forging (MDF) · Severe plastic deformation · Zn–22Al · Silicon · Composite
1 Introduction Due to their high strength, high corrosion resistance, high load-bearing capacity, good fatigue strength, low melting point, excellent castability, appropriate tribological properties, and low-cost, Zn–Al based alloys (ZA series) and in particular the eutectoid ZA22 alloy have been widely used in the applications requiring high mechanical and tribological properties in automotive and aerospace industries [1]. However, due to the coarse dendritic microstructure in ascast condition, ZA alloys exhibit low ductility, low fracture toughness, and heterogeneous mechanical properties [2]. Moreover, their strength is not generally high enough to meet the requirements of some engineering fields [3]. * R. Taghiabadi [email protected] D. Yousefi [email protected] M. H. Shaeri [email protected] I. Ansarian [email protected] 1
Department of Materials Science and Metallurgy, Imam Khomeini International University (IKIU), Qazvin, Iran
On this basis, many efforts have been undertaken to overcome the undesired properties of binary ZA alloys the most important of which are heat treatment [2], alloying addition [3, 4], grain refinement [5, 6], and mechanical/thermomechanical processing [1, 7, 8]. However, it seems that adding alloying elements is the most common approach to improve the basic properties of ZA alloys. Among the investigated elements, Cu is the most common one that is used within the range of 1–3 wt. % to improve the strength, hardness, fracture energy, creep strength, fatigue strength,
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