scholarly journals Effects of Post Heat Treatments on Microstructures and Mechanical Properties of Selective Laser Melted Ti6Al4V Alloy

Metals ◽  
2021 ◽  
Vol 11 (10) ◽  
pp. 1593
Author(s):  
Jianwen Liu ◽  
Jie Liu ◽  
Yixin Li ◽  
Ruifeng Zhang ◽  
Zhuoran Zeng ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Grain Boundary ◽  
Mechanical Performance ◽  
Grain Morphology ◽  
Cross Sectional ◽  
Treatment Processes ◽  
Property Anisotropy ◽  
History Of ◽  
Mechanical Performances ◽  
Non Equilibrium

The unique thermal history of selective laser melting (SLM) can lead to high residual stress and a non-equilibrium state in as-fabricated titanium alloy components and hinders their extensive use. Post heat treatment, as a classical and effective way, could transform non-equilibrium α’ martensite and achieves desirable mechanical performance in SLMed Ti alloys. In this study, we aimed to establish the correlation between the microstructure and mechanical performances of SLMed Ti6Al4V (Ti-64) by using different heat treatment processes. The columnar prior β grain morphology and grain boundary α phase (GB-α) after different heat treatment processes were characterized, with their influences on the tensile property anisotropy fully investigated. Scanning electron microscope (SEM) observation of the fracture surface and its cross-sectional analysis found that the tensile properties, especially the ductility, were affected by the GB-α along the β grain boundary. Furthermore, the discontinuous ratio of GB-α was firstly proposed to quantitatively predict the anisotropic ductility in SLMed Ti-64. This study provides a step forward for achieving the mechanical property manipulation of SLMed Ti-64 parts.

Microstructure of Al-Li Alloy Electron Beam Welding Joint after Post-Weld Heat Treatment

2012 ◽  
Vol 217-219 ◽  
pp. 1921-1927 ◽  
Author(s):  
Shao Gang Wang ◽  
Kuang Yu ◽  
Chuan Xiao Luo ◽  
Li Xing
Keyword(s):  
Heat Treatment ◽  
Electron Beam ◽  
Grain Boundary ◽  
Electron Beam Welding ◽  
Grain Morphology ◽  
Post Weld Heat Treatment ◽  
Joint Fracture ◽  
Δ Phase ◽  
Strengthening Phases ◽  
Weld Heat

Heat treatment was carried out to the 1420 Al-Li alloy electron beam welding (EBW) joints after welding, and the microstructures of welded joints are analyzed systematically before and after post-weld heat treatment (PWHT). The observation of joint microstructure demonstrates that the grain morphology of weldment changes from equiaxed dendrites in as-welded (AW) condition into equiaxed grains after PWHT, and that the fine strengthening phases precipitate within the grain. The XRD analysis of phase constituent and TEM observation of weldment indicate that the main strengthening phases in 1420 Al-Li alloy weldment are spheroidal δ′(Al3Li), β′(Al3Zr) and rod-like T(Al2MgLi) after PWHT. Furthermore, the δ′ phase precipitate free zone (PFZ) is found along the grain boundary. The scanning observation of joint fracture shows that Al-Li alloy EBW joint presents the characteristic of transgranular ductile fracture in AW condition. After PWHT, the Al-Li alloy welded joint presents the pattern of intergranular fracture. The variation of fracture mode is related to dispersed precipitation of δ′ phase and the formation of PFZ at the grain boundary in weldment after heat treatment.

Effect of Optimized Heat Treatments on the Tensile Behavior and Residual Stresses of Selective Laser Melted AlSi10Mg Samples

2019 ◽  
Vol 813 ◽  
pp. 364-369 ◽  
Author(s):  
Chiara Colombo ◽  
Carlo Alberto Biffi ◽  
Jacopo Fiocchi ◽  
Ausonio Tuissi ◽  
Laura Vergani
Keyword(s):  
Heat Treatment ◽  
Residual Stresses ◽  
Mechanical Performance ◽  
Heat Treatments ◽  
Critical Discussion ◽  
Thermal Treatments ◽  
Microstructure Modification ◽  
Main Dimension ◽  
Mechanical Performances ◽  
Plane Scanning

The use of additive manufacturing (AM) technique is recently increased due to its ability in producing complex-shaped components. AlSi10Mg alloy is largely employed for AM and, in particular, for selective laser melting (SLM). Hence, the interest on this alloy is growing, together with the studies to control its mechanical performances, which can be increased by microstructure modification. With this focus, low temperature heat treatments to enhance AlSi10Mg mechanical behavior have been proposed in the recent literature. The present work focuses on two post-additive thermal treatments, with temperatures specifically selected for SLMed AlSi10Mg alloy. The study investigates their effect on mechanical performances, with a particular attention to residual stresses. Experimental measurements of residual stresses obtained by an X-ray diffractometer (XRD) are presented, considering samples produced with their main dimension along the in-plane scanning directions (XY configuration) and the Z direction. Different conditions are accounted: 1) as-built; 2) after heat treatment at 244°C for 180 minutes; 3) after heat treatment at 290°C for 45 minutes. Tensile properties are correlated with the measurements of the residual stresses, allowing for a critical discussion and for a deeper insight on the correlation of the mechanical performance with the process parameters and the following thermal treatments.

Strain-induced martensite effects on transgranular carbide precipitation in type 304 stainless steels

1991 ◽  
Vol 49 ◽  
pp. 604-605
Author(s):  
A.H. Advani ◽  
L.E. Murr ◽  
D. Matlock
Keyword(s):  
Heat Treatment ◽  
Grain Boundary ◽  
Stress Corrosion Cracking ◽  
Stainless Steels ◽  
Deformation Twin ◽  
Austenitic Stainless Steels ◽  
Carbide Precipitation ◽  
Strain Induced Martensite ◽  
Type 304

Thermomechanically induced strain is a key variable producing accelerated carbide precipitation, sensitization and stress corrosion cracking in austenitic stainless steels (SS). Recent work has indicated that higher levels of strain (above 20%) also produce transgranular (TG) carbide precipitation and corrosion simultaneous with the grain boundary phenomenon in 316 SS. Transgranular precipitates were noted to form primarily on deformation twin-fault planes and their intersections in 316 SS.Briant has indicated that TG precipitation in 316 SS is significantly different from 304 SS due to the formation of strain-induced martensite on 304 SS, though an understanding of the role of martensite on the process has not been developed. This study is concerned with evaluating the effects of strain and strain-induced martensite on TG carbide precipitation in 304 SS. The study was performed on samples of a 0.051%C-304 SS deformed to 33% followed by heat treatment at 670°C for 1 h.

High-Temperature Instability of A Cr2Nb-Nb(Cr) Microlaminate Composite

1996 ◽  
Vol 54 ◽  
pp. 374-375
Author(s):  
M. Larsen ◽  
R.G. Rowe ◽  
D.W. Skelly
Keyword(s):  
Heat Treatment ◽  
Solid Solution ◽  
High Temperature ◽  
Elevated Temperatures ◽  
Aircraft Engine ◽  
Lattice Parameter ◽  
Microstructural Stability ◽  
Elevated Temperature Strength ◽  
Cross Sectional ◽  
Bcc Structure

Microlaminate composites consisting of alternating layers of a high temperature intermetallic compound for elevated temperature strength and a ductile refractory metal for toughening may have uses in aircraft engine turbines. Microstructural stability at elevated temperatures is a crucial requirement for these composites. A microlaminate composite consisting of alternating layers of Cr2Nb and Nb(Cr) was produced by vapor phase deposition. The stability of the layers at elevated temperatures was investigated by cross-sectional TEM.The as-deposited composite consists of layers of a Nb(Cr) solid solution with a composition in atomic percent of 91% Nb and 9% Cr. It has a bcc structure with highly elongated grains. Alternating with this Nb(Cr) layer is the Cr2Nb layer. However, this layer has deposited as a fine grain Cr(Nb) solid solution with a metastable bcc structure and a lattice parameter about half way between that of pure Nb and pure Cr. The atomic composition of this layer is 60% Cr and 40% Nb. The interface between the layers in the as-deposited condition appears very flat (figure 1). After a two hour, 1200 °C heat treatment, the metastable Cr(Nb) layer transforms to the Cr2Nb phase with the C15 cubic structure. Grain coarsening occurs in the Nb(Cr) layer and the interface between the layers roughen. The roughening of the interface is a prelude to an instability of the interface at higher heat treatment temperatures with perturbations of the Cr2Nb grains penetrating into the Nb(Cr) layer.

Suicidal Ideation Among Medical Students in Dammam, Saudi Arabia

Crisis ◽  
2020 ◽  
pp. 1-6
Author(s):  
Mohammed Madadin ◽  
Ritesh G. Menezes ◽  
Maha A. Alassaf ◽  
Abdulaziz M. Almulhim ◽  
Mahdi S. Abumadini ◽  
...  
Keyword(s):  
Saudi Arabia ◽  
Medical Students ◽  
Suicidal Ideation ◽  
General Health Questionnaire ◽  
Cross Sectional Study ◽  
Eastern Province ◽  
Cross Sectional ◽  
The Past ◽  
Depression Subscale ◽  
History Of

Abstract. Background: Medical students are at high risk of suicidal ideation. Aim: We aimed to obtain information on suicidal ideation among medical students in Dammam located in the Eastern Province of Saudi Arabia. Method: This cross-sectional study was conducted at the College of Medicine affiliated with Imam Abdulrahman Bin Faisal University in the Eastern Province of Saudi Arabia. Suicidal ideation in the past 12 months was assessed based on responses to four questions in the depression subscale of the General Health Questionnaire 28 (GHQ-28). In addition, data were collected to examine the association of suicidal ideation with various factors. Results: We found that 1 in 3 medical students in the study had suicidal ideation in the past 12 months, while around 40% had lifetime suicidal ideation. Suicidal ideation was associated with feelings of parental neglect, history of physical abuse, and dissatisfaction with academic performance. Limitations: The cross-sectional nature of this study limits its ability to determine causality regarding suicidal ideation. Conclusion: These rates are considerably high when compared with rates from studies in other countries around the world. This study provides a reference in the field of suicidology for this region of Saudi Arabia.

External Validity of SCORS-G Ratings of Thematic Apperception Test Narratives in a Sample of Outpatients and Inpatients

2015 ◽  
Vol 36 (1) ◽  
pp. 58-81 ◽  
Author(s):  
Michelle B. Stein ◽  
Jenelle Slavin-Mulford ◽  
Caleb J. Siefert ◽  
Samuel Justin Sinclair ◽  
Michaela Smith ◽  
...  
Keyword(s):  
Life Events ◽  
Psychiatric Hospitalization ◽  
Clinical Care ◽  
Thematic Apperception Test ◽  
Clinical Samples ◽  
Cross Sectional ◽  
Conduct Disordered ◽  
Global Ratings ◽  
Thematic Apperception ◽  
History Of

Abstract. The Social Cognition and Object Relations Scale-Global Ratings Method (SCORS-G; Stein, Hilsenroth, Slavin-Mulford, & Pinsker-Aspen, 2011 ) is a reliable system for coding narrative data, such as Thematic Apperception Test (TAT) stories. This study employs a cross-sectional, correlational design to examine associations between SCORS-G dimensions and life events in two clinical samples. Samples were composed of 177 outpatients and 57 inpatients who completed TAT protocols as part of routine clinical care. Two experienced raters coded narratives with the SCORS-G. Data on the following clinically relevant life events were collected: history of psychiatric hospitalization, suicidality, self-harming behavior, drug/alcohol abuse, conduct-disordered behavior, trauma, and education level. As expected, the clinical life event variable associated with the largest number of SCORS-G dimensions was Suicidality. Identity and Coherence of Self was related to self-harm history across samples. Emotional Investment in Relationships and Complexity of Representations were also associated with several life events. Clinical applications, limitations of the study, and future directions are reviewed.

DYSLIPIDEMIA IN THYROID DISORDERS

2020 ◽  
Vol 4 (7) ◽  
Author(s):  
Kashish Narula ◽  
Narendra Kumar Dara ◽  
Shyam Lal Meena
Keyword(s):  
Lipid Metabolism ◽  
Thyroid Dysfunction ◽  
Cross Sectional Study ◽  
Control Group ◽  
Thyroid Disorders ◽  
Cross Sectional ◽  
Carbohydrate And Lipid Metabolism ◽  
History Of ◽  
Thyroid Profile ◽  
Basal Energy Expenditure

Background: Thyroid hormones influence nearly all major metabolic pathways. Their most obvious and well-known action is the increase in basal energy expenditure obtained by acting on protein, carbohydrate and lipid metabolism. The lipid metabolism is more influenced by the thyroid hormone. Methods: A cross-sectional study was conducted on 100 patients with suspicion of thyroid disorders were taken as cases. One hundred patients with normal thyroid profile and no history of other chronic diseases were taken as control group. Results: The serum TC, TG and LDL levels in hypothyroid individuals (both overt and subclinical) were significantly higher than euthyroid subjects but the levels were comparable between hyperthyroid and euthyroid group. Conclusion: Dyslipidemias are associated with thyroid disorders, so biochemical screening for thyroid dysfunction in all dyslipidemic patients. Therefore, patients presenting with dyslipidemia are recommended for investigation to explore thyroid dysfunction. Keywords: Thyroid profile, Total cholesterol, Triglycerides and LDL

INFLUENCE THE QUENCHING AND TEMPERING ON THE MICROSTRUCTURE, MECHANICAL PROPERTIES AND SURFACE ROUGHNESS, OF MEDIUM CARBON STEEL

2018 ◽  
Vol 18 (1) ◽  
pp. 125-135
Author(s):  
Sattar H A Alfatlawi
Keyword(s):  
Mechanical Properties ◽  
Heat Treatment ◽  
Surface Roughness ◽  
Carbon Steel ◽  
Cold Water ◽  
Medium Carbon Steel ◽  
Medium Carbon ◽  
Heating And Cooling ◽  
Treatment Processes ◽  
Quenching And Tempering

One of ways to improve properties of materials without changing the product shape toobtain the desired engineering applications is heating and cooling under effect of controlledsequence of heat treatment. The main aim of this study was to investigate the effect ofheating and cooling on the surface roughness, microstructure and some selected propertiessuch as the hardness and impact strength of Medium Carbon Steel which treated at differenttypes of heat treatment processes. Heat treatment achieved in this work was respectively,heating, quenching and tempering. The specimens were heated to 850°C and left for 45minutes inside the furnace as a holding time at that temperature, then quenching process wasperformed in four types of quenching media (still air, cold water (2°C), oil and polymersolution), respectively. Thereafter, the samples were tempered at 200°C, 400°C, and 600°Cwith one hour as a soaking time for each temperature, then were all cooled by still air. Whenthe heat treatment process was completed, the surface roughness, hardness, impact strengthand microstructure tests were performed. The results showed a change and clearimprovement of surface roughness, mechanical properties and microstructure afterquenching was achieved, as well as the change that took place due to the increasingtoughness and ductility by reducing of brittleness of samples.

Microstructural and Mechanical Behaviour Evaluation of Mg-Al-Zn Alloy Friction Stir Welded Joint

2020 ◽  
Vol 17 (3) ◽  
pp. 8150-8159
Author(s):  
Kulwant Singh ◽  
Gurbhinder Singh ◽  
Harmeet Singh
Keyword(s):  
Heat Treatment ◽  
Friction Stir Welding ◽  
Magnesium Alloys ◽  
Mechanical Performance ◽  
Fuel Efficiency ◽  
Research Work ◽  
Grain Structure ◽  
Tensile Fracture ◽  
Friction Stir ◽  
The Impact

The weight reduction concept is most effective to reduce the emissions of greenhouse gases from vehicles, which also improves fuel efficiency. Amongst lightweight materials, magnesium alloys are attractive to the automotive sector as a structural material. Welding feasibility of magnesium alloys acts as an influential role in its usage for lightweight prospects. Friction stir welding (FSW) is an appropriate technique as compared to other welding techniques to join magnesium alloys. Field of friction stir welding is emerging in the current scenario. The friction stir welding technique has been selected to weld AZ91 magnesium alloys in the current research work. The microstructure and mechanical characteristics of the produced FSW butt joints have been investigated. Further, the influence of post welding heat treatment (at 260 °C for 1 h) on these properties has also been examined. Post welding heat treatment (PWHT) resulted in the improvement of the grain structure of weld zones which affected the mechanical performance of the joints. After heat treatment, the tensile strength and elongation of the joint increased by 12.6 % and 31.9 % respectively. It is proven that after PWHT, the microhardness of the stir zone reduced and a comparatively smoothened microhardness profile of the FSW joint obtained. No considerable variation in the location of the tensile fracture was witnessed after PWHT. The results show that the impact toughness of the weld joints further decreases after post welding heat treatment.

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