Effect of Ti addition on microstructure and mechanical properties of Zn-22Al alloy after ECAP

The effect of Ti addition on microstructure and mechanical properties of Zn-22Al eutectoid alloy with 0.15 wt%Ti was investigated.It was observed that the presence of Ti changes the morphology of n phase in the alloy.Addition of Ti to Zn-Al alloy caused the formation of Ti(Zn,Al)_(3);phase.Before applying equal channel angular pressing(ECAP),two times of homogenization treatment were conducted on the alloy.After secondary homogenization,the microstructure consisted of a homogeneous and fine mixture ofαand n phases and the as-cast lamellar structure removed.After homogenization,ECAP was carried out on Ti-containing Zn-22Al alloy.The fraction of high angle grain boundaries increased with increasing the number of ECAP passes.The average grain size reduced from 930 nm after secondary homogenization to 380 nm after 8 passes of ECAP.The texture of the alloy also changed by applying ECAP.Maximum elongation to failure of the homogenized alloy was 135%at a strain rate of 10^(-5)s^(-1)which enhanced to a maximum of 405%at a strain rate of 10^(-3)s^(-1)after 8 passes of ECAP.It was also observed that by conducting ECAP and increasing the number of passes the hardness decreases,which indicates work-softening behavior due to dynamic recovery/recrystallization.

Hot deformation behavior of TC11/Ti-22Al-25Nb dual-alloy in isothermal compression

The high-temperature flow behavior of TCll/Ti-22Al-25 Nb electron beam（EB） weldments was investigated by the isothermal compression tests at the temperature of 900-1060℃ and the strain rate of 0.001-10 s-（-1）.Based on the experimental data,the constitutive equation that describes the flow stress as a function of strain rate and deformation temperature is obtained.The apparent activation energy of deformation is calculated,which decreases with increasing the strain and the value is 334 kJ/mol at strain of 0.90.The efficiency of power dissipation η changes obviously with the variation of deformation conditions.Under the strain rates of 0.01,0.1 and 1 s-（-1）,the value of η increases with increasing the true strain for different deformation temperatures.While the value of η decreases with increasing the strain under the strain rates of 0.001 and 10 s-（-1）.The optimum processing condition is（t（opi）=1060℃,ε（opi）=0.1 s-（-1）） with the peak efficiency of 0.51.Under this deformation,dynamic recrystallization（DRX） is observed obviously in the microstructure of welding zone.Under the condition of 1060℃ and 0.001 s-（-1）,the deformation mechanism is dominated by dynamic recovery（DRV） and the value of η decreases sharply（η=0.02）.The flow instability is predicted to occur since the instability parameter ξ（ε）becomes negative.The hot working process can be carried out safely in the domain with the strain rate of 0.001-0.6 s-（-1） and the temperature of 900-1060℃.

Effect of pre-deformation on microstructures and mechanical properties of high purity Al-Cu-Mg alloy

The effects of pre-deformation following solution treatment on the microstructure and mechanical properties of aged high purity Al-Cu-Mg alloy were studied by tensile test, micro-hardness measurements, transmission electron microscopy and scanning electron microscopy. The micro-hardness measurements indicate that compared with un-deformed samples, the peak hardness is increased and the time to reach peak hardness is reduced with increasing pre-strain. Additionally, a double-peak hardness evolution behavior of cold-rolled （CR） samples was observed during aging. The results of TEM observation show that the number density of S′（Al2CuMg） phase is increased and the size is decreased in CR alloy with increase of pre-strain. The peak hardness and peak strength of the CR alloy are increased because of quantity increasing and refinement of S′ phase and high density dislocation.

Effects of T9I6 thermo-mechanical process on microstructure, mechanical properties and ballistic resistance of 2519A aluminum alloy

The effects of T916 thermo-mechanical process on microstructures, mechanical properties and ballistic resistance of 2519A aluminum alloy were investigated by optical microscopy （OM）, transmission electron microscopy （TEM）, tensile tests and ballistic resistance test. After T916 treatment, the yield strength, tensile strength and elongation rate of 2519A aluminum alloy reach 501 MPa, 540 MPa and 14%, respectively. And the ballistic limit velocity of 2519A-T916 alloy （30 mm in thickness） is 715 rn/s. The microstructure varies near the sidewalls of crater. The interrupted ageing contributes to these excellent properties of the alloy. During T916 process, the precipitation of Guinier Preston （GP） zone is finer and denser during the interrupted ageing, thus resulting in well precipitated strengthening phase.

按动情感的快门——《特别送行》采访前后

现场新闻《特别送行》,摘取的是全国著名劳动模范吕鸿宾的乡亲们为他的遗产外出展览悲壮送行的特写镜头。记下这个永恒的瞬间,不是本人一时的灵感或冲动,乃是长久对主人翁透彻的了解和特定环境的启迪所进发的一束火花。吕鸿宾生前是山东省莒县爱国村党支部书记,全国一至六届人大代表,著名劳动模范。1948年,他响应解放区政府的号召,在本村组织起生产变工组,解决了劳力缺乏的困难,获得显著增产效果。1950年,他被评为劳动模范,参加了全国工农兵劳动模范战斗英雄代表大会。1951年,他在村里组织起合作社。1952年4月,他作为中国农民代表参观团团员赴苏联访问4个月,记下6本、13万字的访苏日记。

High temperature deformation behavior and optimization of hot compression process parameters in TC11 titanium alloy with coarse lamellar original microstructure

The high temperature deformation behaviors of α＋β type titanium alloy TC11 （Ti-6.5Al-3.5Mo-1.5Zr-0.3Si） with coarse lamellar starting microstructure were investigated based on the hot compression tests in the temperature range of 950-1100 ℃ and the strain rate range of 0.001-10 s-1. The processing maps at different strains were then constructed based on the dynamic materials model, and the hot compression process parameters and deformation mechanism were optimized and analyzed, respectively. The results show that the processing maps exhibit two domains with a high efficiency of power dissipation and a flow instability domain with a less efficiency of power dissipation. The types of domains were characterized by convergence and divergence of the efficiency of power dissipation, respectively. The convergent domain in a＋fl phase field is at the temperature of 950-990 ℃ and the strain rate of 0.001-0.01 s^-1, which correspond to a better hot compression process window of α＋β phase field. The peak of efficiency of power dissipation in α＋β phase field is at 950 ℃ and 0.001 s 1, which correspond to the best hot compression process parameters of α＋β phase field. The convergent domain in β phase field is at the temperature of 1020-1080 ℃ and the strain rate of 0.001-0.1 s^-l, which correspond to a better hot compression process window of β phase field. The peak of efficiency of power dissipation in ℃ phase field occurs at 1050 ℃ over the strain rates from 0.001 s^-1 to 0.01 s^-1, which correspond to the best hot compression process parameters of ,8 phase field. The divergence domain occurs at the strain rates above 0.5 s^-1 and in all the tested temperature range, which correspond to flow instability that is manifested as flow localization and indicated by the flow softening phenomenon in stress-- strain curves. The deformation mechanisms of the optimized hot compression process windows in a＋β and β phase fields are identified to be spheroidizing and dynamic recrystallizing controlled by self-diffusion mechanism, respectively. The microstructure observation of the deformed specimens in different domains matches very well with the optimized results.

睹物思人 见微知著——现场新闻《特别送行》评析

现场新闻《特别送行》,写的是全国著名劳动模范吕鸿宾的乡亲们为他的遗物外出展览送行的场面。伟大出自平凡。在一篇800多字的现场新闻中要表现出一位平凡人的伟大来,自然要写他的生动事迹。而吕鸿宾这位中国农民的优秀代表,其一生的事迹是不胜枚举的。1948年,他响应政府的号召,在村里组织起生产变工组,解决了劳力缺乏的困难,获得了显著的增产效果。1950年,

Research progress on microstructure evolution and hot processing maps of high strength β titanium alloys during hot deformation

High strength β titanium alloys are widely used in large load bearing components in the aerospace field. At present, large parts are generally formed by die forging. Different initial microstructures and deformation process parameters will significantly affect the flow behavior. To precisely control the microstructures, researchers have conducted many studies to analyze the microstructure evolution law and deformation mechanism during hot compression. This review focuses on the microstructure evolution of high strength β titanium alloys during hot deformation, including dynamic recrystallization and dynamic recovery in the single-phase region and the dynamic evolution of the α phase in the two-phase region. Furthermore, the optimal hot processing regions, instability regions,and the relationship between the efficiency of power dissipation and the deformation mechanism in the hot processing map are summarized. Finally, the problems and development direction of using hot processing maps to optimize process parameters are also emphasized.

Hot working behavior of near alpha titanium alloy analyzed by mechanical testing and processing map

The hot deformation characteristics of the Ti-5.7Al-2.1Sn-3.9Zr-2Mo-0.1Si(Ti-6242S)alloy with an acicular starting microstructure were analyzed using processing map.The uniaxial hot compression tests were performed at temperatures ranging from 850 to 1000℃and at strain rates of 0.001-1 s-1.The developed processing map was used to determine the safe and unsafe deformation conditions of the alloy in association with the microstructural evolution by SEM and OM.It was recognized that the flow stress revealed differences in flow softening behavior by deformation at 1000℃compared to the lower deformation temperatures,which was attributed to microstructural changes.The processing map developed for typical strain of 0.7 in two-phase field exhibited high efficiency value of power dissipation of about 55%at 950℃and 0.001 s-1,basically due to extensive globularization.An increase in strain rate and a decrease in temperature resulted in a decrease in globularization ofαlamellae,whileαlamellar kinking increased.Eventually,the instability domain of flow behavior was identified in the temperature range of 850-900℃and at the strain rate higher than 0.01 s-1 reflecting the flow localization and adiabatic shear banding.By considering the power efficiency domains and the microstructural observations,the deformation in the temperature range of 950-1000℃and strain rate range of 0.001-0.01 s-1 was desirable leading to high efficiencies.It was realized that(950℃,0.001 s-1)was the optimum deformation condition for the alloy.

Hot workability and dynamic recrystallization mechanisms of pure nickel N6

The hot workability and dynamic recrystallization(DRX)mechanisms of pure nickel N6 were systematically investigated using hot compression tests.Based on hot compression data,the constitutive equation of N6 was developed and its reliability was verified.Its hot processing map was constructed,and combined with microstructural observations,a semi-quantitative response relationship between hot deformation parameters and microstructure was established.The DRX process of N6 is a thermally activated process and particularly sensitive to the strain rate.The optimal hot processing parameters for N6 were determined to be 950−1050℃ and 0.1−1 s^(−1).Furthermore,it was proven that the dominant nucleation mechanism is discontinuous DRX characterized by grain boundary bulging and twins assisting nucleation,while the continuous DRX characterized by subgrains combined with rotation is an inactive nucleation mechanism.

Influence of multipass high rotating speed friction stir processing on microstructure evolution,corrosion behavior and mechanical properties of stirred zone on AZ31 alloy

The influence of multipass high rotating speed friction stir processing(FSP)on the microstructure evolution,corrosion behavior,and tensile properties of the stirred zone(SZ)was investigated by EBSD,TEM,SEM,electrochemical workstation and electronic universal testing machine.The mean grain size of the SZ is significantly refined,and it increases with the increase of the processing pass.In addition to an obvious increase in the number,the distribution ofβ-Al12Mg17 precipitates also becomes more uniform and dispersed with increasing the processing pass.Compared with the as-received AZ31 alloy,the tensile properties of the SZ are hardly improved,but the corrosion resistances are significantly enhanced.The corrosion potential of the SZ prepared by 4-pass FSP is increased from−1.56 V for the unprocessed AZ31 alloy to−1.19 V,while the corrosion current is decreased from 1.55×10^−4 to 5.47×10^−5 A.

Hot deformation behaviors and processing maps of Mg-Zn-Er alloys based on Gleeble-1500 hot compression simulation

The hot deformation behaviors of as-solution Mg?xZn?yEr alloys (x/y=6, x=3.0, 4.5 and 6.0; y=0.50, 0.75 and 1.00) wereinvestigated on Gleeble?1500 thermal simulator in a temperature range of 200?450 °C at a strain rate of 0.001?1 s?1. The truestress?strain curves showed the dynamic competition between the working hardening and working softening mainly due to thedynamic recrystallization (DRX) occurring during hot compression. The constitutive equations were constructed which couldaccurately predict the peak stress of the alloys. The addition of Zn and/or Er resulted in higher deformation activation energy forMg?3Zn?0.5Er (alloy A). The processing maps were constructed as function of the temperature and the strain rate, providing theoptimum hot working conditions (i.e., at strain of 0.3, Mg?3Zn?0.5Er (alloy A): 380?430 ?C, <0.1 s?1; Mg?4.5Zn?0.75Er (alloy B):380?450 ?C, 0.01?0.1 s?1; Mg?6Zn?1Er (alloy C): 390?440 ?C, 0.01?0.1 s?1). The as-solution treated Mg?4.5Zn?0.75Er (alloy B)demonstrated more optimum hot working window comparing with Mg?3Zn?0.5Er (alloy A) and Mg?6Zn?1Er (alloy C).

Could Acceptance Predict Commitment in Organisational Change？ Impact of Changes Caused by Succession From the Viewpoint of Non-family Employees in Small Family Firms

Family business predecessor announced to staff that with his son, he is going to commence a succession process in the family firm. Two of the key employees rose and announced their intention to leave the company after the predecessor passed leadership of the firm to successor. In a firm with a total number of nine employees, such a situation can prove catastrophic. Why did these employees react that way？ What is behind their motivation？ Using these two employees as examples, this study discusses the elements which influence the development and continuance of employees＇ organisational commitment. Inspired by the example, this study gives answers by means of qualitative research methods to the following research questions： Could acceptance predict the development and continuation of organisational commitment during a process of organisational change and how do the concepts of psychological acceptance adaptation and organisational commitment link together in employee cognitive processing during organisational change？ The empirical setting of this study includes seven small family fLrms and the study has carded out an overview of family business succession （FBS） from the viewpoint of non-family employees in Finnish and Irish family firms. Results of the study indicate how employees＇ commitment forms and changes during a certain change process. A key element for development and the continuance of commitment is acceptance. As an outcome of this paper, a new model will be developed where acceptance, adaptation, and commitment （AAC-model） are combined, in essence, three dimensions （functional, legal-economic, and psychological） of changes in FBS.

Influence of rheo-diecasting processing parameters on microstructure and mechanical properties of hypereutectic Al-30%Si alloy

The effects of pouring temperature,vibration frequency,and the number of curves in a serpentine channel,on themicrostructure and mechanical properties of Al-30%Si alloy processed by rheo-diecasting(RDC)were investigated.The semisolidAl-30%Si alloy slurry was prepared by vibration serpentine channel pouring(VSCP)process in the RDC process.The results showthat the pouring temperature,the vibration frequency,and the number of the curves strongly affect the microstructure and mechanicalproperties of Al-30%Si alloy.Under experimental conditions of a pouring temperature of850°C,a twelve-curve copper channel anda vibration frequency of80Hz,the primary Si grains are refined into fine compact grains with average grain size of about24.6μm inthe RDC samples assisted with VSCP.Moreover,the ultimate tensile strength(UTS),elongation and hardness of the RDC sample are296MPa,0.87%and HB155,respectively.It is concluded that the VSCP process can effectively refine the primary Si grains.Therefinement of primary Si grains is the major cause for the improvement of the mechanical properties of the RDC sample.

Evolution of microstructure in semi-solid slurries of rheocast aluminum alloy

Semi-solid metal processing is being developed in die casting applications to give several cost benefits. To efficiently apply this emerging technology, it is important to understand the evolution of microstructure in semi-solid slurries for the control of the theological behavior in semi-solid state. An experimental apparatus was developed which can capture the grain structure at different times at early stages to understand how the semi-solid structure evolves. In this technique, semi-solid slurry was produced by injecting fine gas bubbles into the melt through a graphite diffuser during solidification. Then, a copper quenching mold was used to draw some semi-solid slurry into a thin channel. The semi-solid slurry was then rapidly frozen in the channel giving the microstructure of the slurry at the desired time. Samples of semi-solid 356 aluminum alloy were taken at different gas injection times of 1, 5, 10, 15, 20, 30, 35, 40, and 45 s. Analysis of the microstructure suggests that the fragmentation by remelting mechanism should be responsible for the formation of globular structure in this rheocasting process.

Microstructure and mechanical behavior of Ti−Cu alloys produced by semisolid processing

The mechanical properties of Ti−Cu alloys processed via thixoforming were evaluated.Ti−Cu(25,27,and 29 wt.%Cu)ingots were produced via arc melting,homogenization at 950℃ for 24 h,and hot-forging at 900℃,followed by thixoforming at a speed of 8 mm/s after isothermal heat treatment at 1035℃ for 300 s.The thixoformed alloys exhibited good mechanical strength,limited plasticity under tensile loading,and reasonable plasticity under compressive loading.The mechanical strength and plasticity decreased as the Cu content increased as a result of the increasing volume fraction of the peritectic Ti_(2)Cu phase(transformed liquid),which exhibited a lower strength and plasticity than theα+Ti_(2)Cu regions(transformed solid).These findings indicated that the trade-off between the mechanical properties and semisolid processability is largely governed by the Cu content.

Microstructure and mechanical properties evolution of 65Cu-35Zn brass tube during cyclic rotating−bending process

The cyclic rotating−bending(CRB)processes under different deformation conditions were carried out to refine the microstructure and improve the mechanical properties of the 65Cu−35Zn brass tubes.The microstructure and the mechanical properties in the axial direction of the tubes after the CRB process were studied with the OM,EBSD and conventional tensile test.To obtain the accumulated effective plastic strain of the tube during the CRB process,the FEM simulation was also executed.The results show that the average grain size decreases with the increase of rotation time at RT,and with the decrease of bending angle at 200℃.With the increase of accumulated effective plastic strain during the CRB process,the reduction rate of average grain size of the brass tube increases,the tensile strength of the brass tube increases in wave shape and the elongation increases first and then sharply decreases.

Application of Wind Generation on Weak Networks Considering Potential System Limitations Due to Transients and Faults

Limited resources are available on the application of wind generation systems interconnected to weak powemetworks. With the need to further interface DG （distributed generation） including WG （wind generation） to weak networks, it is necessary to establish a means of determining what is the most efficient quantity of WG that can be applied in order to maintain stability in the network. This paper establishes a concept that can be applied to weak networks. The aim is to estimate how much WG can be installed on weak networks as well as establishing characteristic responses to generation loss without and with faulted conditions. The main contribution is a thorough understanding of weak network limitation proved to be the most critical parameter in these calculations.

Regenerative medicine technology applied to gastroenterology:Current status and future perspectives

This special issue of World Journal of Gastroenterology has been conceived to illustrate to gastroenterology operators the role that regenerative medicine(RM) will have in the progress of gastrointestinal(GI) medicine.RM is a multidisciplinary field aiming to replace,regenerate or repair diseased tissues or organs.The past decade has been marked by numerous ground-breaking achievements that led experts in the field to manufacture functional substitutes of relatively simple organs.This progress is paving the ground for investigations that aims to the bioengineering and regeneration of more complex organs like livers,pancreas and intestine.In this special issue,the reader will be introduced,hand-in-hand,to explore the field of RM and will be educated on the progress,pitfalls and promise of RM technologies as applied to GI medicine.

Structural Changes That Generate Competitive Ability to the Metal Working Industry

This article presents the results of a study conducted in a Metallurgical industry located in the town of Santa Rosa--Rio Grande do Sul State, Brazil. Its central goal was to obtain a better understanding of the structural changes in the organization and identify its working practices through both case and bibliographic studies, taking into consideration the technological advances and the new management being implemented in the company, due to its acquisition by a multinational company. The proposal of a new organizational structure which has brought inevitable changes to the organizations but the structure needs to be well defined to lead to the company under study and its employees the best way, through continuous improvement and competitive entrepreneurship. The results obtained enable a better understanding of the history and nature of changes in the organization, considering it as a living and changing system.