scholarly journals Micro-Shear Bands and Their Enhancement on High Temperature Strength of Mg-Gd-Y-Zr Alloy

Materials ◽  
2021 ◽  
Vol 14 (12) ◽  
pp. 3262
Author(s):  
Hongchao Xiao ◽  
Zhengjiang Yang ◽  
Jie Li ◽  
Yingchun Wan
Keyword(s):  
Mechanical Properties ◽  
Fracture Behavior ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
Shear Bands ◽  
Aging Treatment ◽  
Deformation Mode ◽  
High Temperature Strength ◽  
Subsequent Aging ◽  
Zr Alloy

When Mg-Gd-Y-Zr alloy is cold forged, a large number of nano-micro shear bands are formed inside the grains. It is observed that micro-shear bands hinder the sliding of dislocations, resulting in an increase in tensile strength at elevated temperatures. The subsequent aging treatment further strengthens the alloy. Compared with unforged aged alloys, aged samples with pre-generated micro-shear bands exhibit higher strength at room temperature to 250 °C, but exhibit similar properties at higher temperatures. Microstructure characterization and fracture behavior analysis indicate that the transformation of deformation mode from dislocation sliding to grain boundary activity is mainly due to the change of mechanical properties with temperature. In addition, the alloy precipitates with the aid of dislocations during tension, and exhibits higher strength at 200 °C than that at room temperature.

Influence of aging on mechanical properties of equal channel angular pressed aluminum alloy 7075

2015 ◽  
Vol 231 (10) ◽  
pp. 1803-1811 ◽  
Author(s):  
Seyed Mahmoud Ghalehbandi ◽  
Alireza Fallahi Arezoodar ◽  
Hossein Hosseini-Toudeshky
Keyword(s):  
Mechanical Properties ◽  
Aluminum Alloy ◽  
Equal Channel Angular Pressing ◽  
Room Temperature ◽  
Solution Treatment ◽  
Aging Treatment ◽  
Subsequent Aging ◽  
Good Ductility ◽  
Angular Pressing ◽  
Aluminum Alloy 7075

Effect of aging treatment on mechanical properties of an age-hardenable aluminum alloy after equal channel angular pressing at room temperature has been investigated using hardness, stress–strain behavior and surface fractography. Aluminum alloy 7075 was pressed after solution treatment. Yield stress, ultimate stress and hardness of pressed samples have increased significantly compared with those of coarse grain, but the elongation to failure has decreased. Also the pressed specimens were subjected to aging treatment at room temperature and temperatures of 80 °C, 100 °C, 120 °C and 140 °C to obtain the optimized strength and ductility. The results indicated that post–equal channel angular pressing aging at 80 °C has resulted in the maximum strength, and natural aging has resulted in good ductility and acceptable strength. It confirmed the fact that there is a potential in obtaining high strength and good ductility in age-hardenable alloys employing severe plastic deformation and subsequent aging.

Mechanical Properties and Microstructure of the Newly Developed Steel (Low C 18Cr-11Ni-3Cu-Mo-Nb-B-N) After Aging Treatment

2020 ◽  
Author(s):  
Nao Otaki ◽  
Tomoaki Hamaguchi ◽  
Takahiro Osuki ◽  
Yuhei Suzuki ◽  
Masaki Ueyama ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
High Temperature ◽  
Vickers Hardness ◽  
Elevated Temperatures ◽  
Rupture Strength ◽  
Aging Treatment ◽  
High Strength ◽  
High Temperature Strength ◽  
Short Term ◽  
Rich Phase

Abstract In petroleum refinery plants, materials with high sensitization resistance are required. 347AP has particularly been developed for such applications and shows good sensitization resistance owing to its low C content. However, further improvement in high temperature strength is required for high temperature operations in complex refineries, such as delayed cokers. Recently, a new austenitic stainless steel (low C 18Cr-11Ni-3Cu-Mo-Nb-B-N, UNS No. S34752) with high sensitization resistance and high strength at elevated temperatures has been developed. In this study, the mechanical properties and microstructures of several aged specimens will be reported. By conducting several aging heat treatments in the range of 550–750 °C for 300–10,000 h on the developed steel, it was revealed that there were only few coarse precipitates that assumed sigma phase even after aging at 750 °C for 10,000 h. This indicates that the newly developed steel has superior phase stability. The developed steel drastically increased its Vickers hardness by short-term aging treatments. Through transmission electron microscopy observations, the fine precipitates of Cu-rich phase were observed dispersedly in the ruptured specimen. Therefore, the increase in Vickers hardness in short-term aging is possibly owing to the dispersed precipitation of Cu-rich phase. There was further increase in Vickers hardness owing to Z phase precipitation; however, the increment was smaller than that caused by Cu-rich phase. The newly developed alloy demonstrated excellent creep rupture strength even in the long-term tests of approximately 30,000 h, which is attributed to these precipitates.

Effect of Pre-Aging on the Microstructure and Strength of Supersaturated AlZnMg Alloys Processed by ECAP

2008 ◽  
Vol 584-586 ◽  
pp. 501-506 ◽  
Author(s):  
Nguyen Q. Chinh ◽  
Jenő Gubicza ◽  
Tomasz Czeppe ◽  
Janos Lendvai ◽  
Zoltán Hegedűs ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Solution Heat Treatment ◽  
Room Temperature ◽  
Shear Bands ◽  
Natural Aging ◽  
Al Alloys ◽  
Interesting Application ◽  
Subsequent Aging ◽  
Angular Pressing ◽  
Time Periods

This work is focused on the effect of the combination of natural aging and severe plastic deformation (SPD) produced by Equal-Channel Angular Pressing (ECAP) on the microstructure and strength of supersaturated AlZnMg alloys. Following a solution heat-treatment and quenching into water at room temperature, samples were naturally aged for different time periods and then processed by ECAP. The microstructure and mechanical properties of these samples are described and discussed. This investigation leads to proposing an interesting application of ECAP for supersaturated alloys. Using the shear bands created by ECAP in only one pass and applying appropriate subsequent aging treatments, composite-like microstructures can be achieved in conventional age-hardenanble Al alloys.

scholarly journals Deformation Mechanism, Microstructure, and Mechanical Properties Evolution of Mg–Gd–Y–Zr Alloy during Cold Torsion

Materials ◽  
2021 ◽  
Vol 14 (8) ◽  
pp. 2067
Author(s):  
Hongchao Xiao ◽  
Zhengjiang Yang ◽  
Jie Li ◽  
Yingchun Wan
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Basal Slip ◽  
Room Temperature ◽  
Deformation Mode ◽  
Equivalent Strain ◽  
Mechanical Tests ◽  
Fiber Texture ◽  
Basal Pole ◽  
Zr Alloy

Mg–Gd–Y–Zr alloy was subjected to torsion of various strain levels at room temperature. Obvious traces of basal slip were observed in the twisted alloy. Dislocations of <c+a> were also observed, but there were no signs of significant sliding. Even in the sample whose equivalent strain became 0.294, 101¯0 twinning and 101¯2 twinning were rarely seen. The deformation mode with predominant basal <a> dislocations and subordinate <c+a> dislocations resulted in a modified Y fiber texture with a basal pole slightly dispersed at about 70° from the twist axis. Mechanical tests revealed that the tensile strength and compressive strengths increased simultaneously after twisting.

Mechanical Properties and Dislocation Structure of Single Crystal Cdte Deformed in Compression at 300°C

1976 ◽  
Vol 34 ◽  
pp. 592-593
Author(s):  
Ernest L. Hall ◽  
J. B. Vander Sande
Keyword(s):  
Mechanical Properties ◽  
Single Crystal ◽  
Dislocation Structure ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
Strain Curve ◽  
Optical Devices ◽  
Semiconductor Compound ◽  
Wide Range ◽  
Sample Orientation

The present paper describes research on the mechanical properties and related dislocation structure of CdTe, a II-VI semiconductor compound with a wide range of uses in electrical and optical devices. At room temperature CdTe exhibits little plasticity and at the same time relatively low strength and hardness. The mechanical behavior of CdTe was examined at elevated temperatures with the goal of understanding plastic flow in this material and eventually improving the room temperature properties. Several samples of single crystal CdTe of identical size and crystallographic orientation were deformed in compression at 300°C to various levels of total strain. A resolved shear stress vs. compressive glide strain curve (Figure la) was derived from the results of the tests and the knowledge of the sample orientation.

On the use of Ozawa/Flynn/Wall method to determine aging activation energy for elastomers

2021 ◽  
pp. 009524432110203
Author(s):  
Sudhir Bafna
Keyword(s):  
Mechanical Properties ◽  
Activation Energy ◽  
Weight Loss ◽  
Oxygen Consumption ◽  
Dwell Time ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
Degradation Mechanism ◽  
Kinetics Of ◽  
Wall Method

It is often necessary to assess the effect of aging at room temperature over years/decades for hardware containing elastomeric components such as oring seals or shock isolators. In order to determine this effect, accelerated oven aging at elevated temperatures is pursued. When doing so, it is vital that the degradation mechanism still be representative of that prevalent at room temperature. This places an upper limit on the elevated oven temperature, which in turn, increases the dwell time in the oven. As a result, the oven dwell time can run into months, if not years, something that is not realistically feasible due to resource/schedule constraints in industry. Measuring activation energy (Ea) of elastomer aging by test methods such as tensile strength or elongation, compression set, modulus, oxygen consumption, etc. is expensive and time consuming. Use of kinetics of weight loss by ThermoGravimetric Analysis (TGA) using the Ozawa/Flynn/Wall method per ASTM E1641 is an attractive option (especially due to the availability of commercial instrumentation with software to make the required measurements and calculations) and is widely used. There is no fundamental scientific reason why the kinetics of weight loss at elevated temperatures should correlate to the kinetics of loss of mechanical properties over years/decades at room temperature. Ea obtained by high temperature weight loss is almost always significantly higher than that obtained by measurements of mechanical properties or oxygen consumption over extended periods at much lower temperatures. In this paper, data on five different elastomer types (butyl, nitrile, EPDM, polychloroprene and fluorocarbon) are presented to prove that point. Thus, use of Ea determined by weight loss by TGA tends to give unrealistically high values, which in turn, will lead to incorrectly high predictions of storage life at room temperature.

Microstructure Evolution and Mechanical Properties of the Ni/Ni Soldered Joints

2011 ◽  
Vol 172-174 ◽  
pp. 863-868
Author(s):  
Anna Sypień ◽  
Andrzej Piątkowski ◽  
Paweł Zięba
Keyword(s):  
Mechanical Properties ◽  
Shear Strength ◽  
Chemical Composition ◽  
Microstructure Evolution ◽  
Fracture Behavior ◽  
Bulk Solder ◽  
Subsequent Aging ◽  
Brittle Phase ◽  
Edx Microanalysis ◽  
Solder Interface

The paper presents the results of studies on the microstructure, chemical composition and mechanical properties of the Ni/SnAuCu/Ni interconnections obtained due to the conventional soldering at 300 °C for different times and subsequent aging at 150 °C. The EDX microanalysis allowed to detect at the Ni/solder interface the (Ni,Cu,Au)3Sn4phase which transformed to (Cu,Ni,Au)6Sn5after longer time of soldering. In the central part of the interconnection AuSn4brittle phase was present. This phase was responsible for the significant decrease of the shear strength in the joints subjected to aging at 150 °C for 1000h, 1500 hours. The fracture behavior of such joints appeared to be caused partly by the coalescence of the microvoids in the bulk solder, cleavage of η-phase grains and decohesion at the interface.

Martensite decomposition during post-heat treatments and the aging response of near-α Ti–6Al–2Sn–4Zr–2Mo (Ti-6242) titanium alloy processed by selective laser melting (SLM)

2021 ◽  
pp. 2050018
Author(s):  
Haiyang Fan ◽  
Yahui Liu ◽  
Shoufeng Yang
Keyword(s):  
Titanium Alloy ◽  
High Temperature ◽  
Titanium Alloys ◽  
Selective Laser Melting ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
Aging Treatment ◽  
Water Quenching ◽  
Laser Melting ◽  
Aging Response

Ti–6Al–2Sn–4Zr–2Mo (Ti-6242), a near-[Formula: see text] titanium alloy explicitly designed for high-temperature applications, consists of a martensitic structure after selective laser melting (SLM). However, martensite is thermally unstable and thus adverse to the long-term service at high temperatures. Hence, understanding martensite decomposition is a high priority for seeking post-heat treatment for SLMed Ti-6242. Besides, compared to the room-temperature titanium alloys like Ti–6Al–4V, aging treatment is indispensable to high-temperature near-[Formula: see text] titanium alloys so that their microstructures and mechanical properties are pre-stabilized before working at elevated temperatures. Therefore, the aging response of the material is another concern of this study. To elaborate the two concerns, SLMed Ti-6242 was first isothermally annealed at 650[Formula: see text]C and then water-quenched to room temperature, followed by standard aging at 595[Formula: see text]C. The microstructure analysis revealed a temperature-dependent martensite decomposition, which proceeded sluggishly at [Formula: see text]C despite a long duration but rapidly transformed into lamellar [Formula: see text] above the martensite transition zone (770[Formula: see text]C). As heating to [Formula: see text]C), it produced a coarse microstructure containing new martensites formed in water quenching. The subsequent mechanical testing indicated that SLM-built Ti-6242 is excellent in terms of both room- and high-temperature tensile properties, with around 1400 MPa (UTS)[Formula: see text]5% elongation and 1150 MPa (UTS)[Formula: see text]10% elongation, respectively. However, the combination of water quenching and aging embrittled the as-built material severely.

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