Mg-Ca基合金研究

1．Mg-Ca二元合金相图：

Ca在镁中的溶解度在515oC时是1.34%（重量），但是到200oC时几乎为0。 铸态相结构：α-Mg+(α-Mg, Mg2Ca)共晶

1. A Study of Homogenization and Precipitation Hardening Behaviour of

Mg-Ca-Zn Alloys

A thesis presented to the University of Waterloo in fulfillment of the thesis requirement for the degree of Master of Applied Science

In Mechanical Engineering Waterloo, Ontario, Canada, 2008 Ashkan Shadkam

一．合金成分：

二．

Mg-Ca binary alloy: heat treatment:

Mg-Ca-Zn ternary alloy: heat treatment:

组织腐蚀剂：

One etchant however, acetic glycol（醋酸乙二醇）（1ml，20ml醋酸，60ml乙二醇和20ml水）(1 ml HNO3, 20 ml acetic acid, 60 ml ethylene glycol and 20 ml water)

reveals grain boundaries and is suitable for revealing more

microstructural details. Dilute HNO3 is also used [Levi et al. 2006]. Although two etchants do not differ much in terms of revealing microstructural characteristics, HNO3 reveals needle-shaped features not exposed by acetic glycol etchant.

一、 Mg-2.5Ca 铸态、固溶及时效组织

铸态组织

铸态组织

固溶态组织 腐蚀 抛光

时效1750C6小时

Mg-2.5Ca 时效硬化曲线

铸态Mg-2.5Ca XRD

二、 Mg-2Ca-1Zn 铸态、固溶及时效组织、时效硬化曲线

Mg-2Ca-1Zn 时效硬化曲线

三、

Mg-2Ca-2Zn 铸态、固溶及时效组织、时效硬化曲线

Mg-2Ca-2Zn 铸态组织，所有的为

抛光

三个合金硬化曲线比较 (a) Mg-2.5Ca, (b) Mg-2Ca-1Zn, ( c) Mg-2Ca-2Zn

a b c

结论：加Zn之后，大大增强了Mg-Ca合金的时效硬化效应。

7.2 Suggestions for the Future Work

The recommendations to further study microstructural characteristics and aging response of the alloys are summarized as follows: TEM investigations of the as-cast and homogenized alloys are recommended. In the binary alloy it will help determine

microstructural changes in the eutectic mixture. In the case of ternary alloys, studying grain boundary particles after homogenization heat treatment with the aid of diffraction patterns, will determine how zinc participate in the Laves phases in these particle.

For each alloy of the present investigation, with aid of presented hardness evolution during DSC, shape and orientation relationships of the hardening phase can be determined by TEM investigations.

The sample used for the isothermal calorimetry trace of the binary Mg-3Ca at 220°C, is suggested be studied by the TEM to investigate whether precipitation occurs homogeneously within _-Mg grains or the large exothermic heat effect at this temperature is due to precipitation on already available Mg2Ca particles. It will also help determine number density of precipitates and orientation relationship of Mg2Ca with the magnesium matrix. Either IC samples of the ternary alloys at 200°C or 220°C is suggested be studied by TEM to investigate precipitates evolved during the IC test. This will shed light on the number density and types of precipitates and that evolve during aging. The role of calcium in the precipitation response of the ternary alloys can be determined by studying the hardness evolution in the alloys containing higher percentages of calcium, i.e. higher calcium content than 2.5 wt%.

Tensile tests on the homogenized and aged samples are suggested be performed to study effect of aging on the mechanical behavior of the alloys of the present investigation.

2. The Effect of Zn Additions on Precipitation Hardening of Mg-Ca Alloys

Brian Langelier, Shahrzad Esmaeili

University of Waterloo; 200 University Avenue West; Waterloo, Ontario, N3L 3G1, Canada

一、合金成分：

二．热处理：固溶分两段式，二元合金为315oC 5小时，然后505oC 24小时；

三元合金：315oC 5小时然后480oC24小时。 时效：200oC 0到7小时

三、硬化曲线

这一硬化曲线似乎与上一文献（文献一与文献二为同一个工作）的曲线相矛盾，文献一中的Mg-2Ca-1Zn的最高硬度在200oC时为70HV，而此文献中为83HV。

四．计算的相图

Mg-Ca二元相图

Zn含量为0.9时的Mg-Ca-Zn三元相图

Zn含量为1.8%时的Mg-Ca-Zn三元相图

结论：在所研究的合金中的硬化效应主要是由Ca2Mg6Zn3，及Mg2Ca所提

供。

3. Trans．Nonferrous Met．Soc．China 18(2008)s101一s106 Microstructures and properties ofrapidly solidified Mg--Zn--Ca alloys

ZHOU Tao(盾J涛)，CHEN Ding(陈鼎)，CHEN Zhen．hua(陈振华) 材料：Rapidly solidified Mg-6Zn-xCa (x=3，5，7.5,10)

200oC72小时时效后与200oC 退火1小时具有同样的相组成

4. Precipitation Hardening in Mg-Ca-Zn Alloys

M. BAMBERGER, G. LEVI, and J.B. VANDER SANDE METALLURGICAL AND MATERIALS TRANSACTIONS A VOLUME 37A, FEBRUARY 2006—481

合金成分选择依据（标准）：

（1） 在相图上低于镁合金的熔点温度（650°C ）的150 °C to 200 °C之间存在

一个相对较大的单相区

（2） 在室温时相比较少，这样可以保证时效硬化的条件 根据上述标准，设计的合金成分为：

热处理：（1）固溶：为了不使晶界的低熔点晶间共晶相在固溶过程中溶解，固溶采用两段式，

首先在300 °C保温48小时，然后以0.02 °C/min 的速度加热到465 °C保温96小时，（2）时效：175 °C， 2 to 144 hours

采用ThermolCalc 计算的Mg-Ca-Zn在465oC时的等温面三元相图。

本试验中的合金设计。从此相图中可以看出A,B合金在465oC时为-Mg与Mg2Ca两相合金，C和D为-Mg单相合金

XRD 测试结果显示：A合金固溶之后为-Mg与Mg2Ca两相共存 在D合金中只有极少量的Mg2Ca相，几乎是-Mg单相

对于A合金，计算的相重量分数与温度的关系，可以看出在465oC时组织是-Mg与Mg2Ca两相共存，而对于D合金，465oC时是-Mg单相。

固溶组织显示：A合金为两相共存，D合金为单相，以上设计结果，计算结果，组织分析结果及XRD分析结果都表明A合金为两项共存，D合金为单相。

经过计算得知在A,B,D三种合金中175oC的沉淀析出相为Ca2Mg6Zn3, 同时A ，B中还有Mg2Ca，而在C合金中仅有Mg2Ca沉淀析出，说明A,B,D三种合金的硬化反应得益于Ca2Mg6Zn3，而Mg2Ca的硬化效应就要弱一些。

结论：在本试验中所设计的合金中的硬化相为Ca2Mg6Zn3，而非Mg2Ca。

5. Solidification, solution treatment and age hardening of a Mg–1.6 wt.%

Ca–3.2 wt.% Zn alloy

G. Levi S.Avraham, .Zilberovand M. Bamberger Acta Materialia

Volume 54, Issue 2, January 2006, Pages 523-530

Abstract

Based on thermodynamic calculations, a die-cast Mg–1.6 wt.% Ca–3.2 wt.% Zn alloy was solution treated at 465 °C and aged at 150, 175, 200 and 225 °C for 1–96 h. In

addition, cast samples were exposed to 200 and 225 °C for up to 32 days. The microstructures of the as-cast,

solution-treated and aged alloys are in good agreement with the thermodynamic calculations. A typical age hardening and softening response was obtained during the aging treatment, as well as during the exposure to elevated temperatures. The alloy hardening correlates to the precipitation of Ca2Mg6Zn3.

6. Scripta Materialia 51 (2004) 193–197

Enhanced age-hardening behaviour in Mg–4 wt.% Zn micro-alloyed with Ca

C.J. Bettles, M.A. Gibson *, K. Venkatesan

一．合金成分：

Mg–4 wt.% Zn- 0.35 wt.% Ca- 0.5 wt.% Zr

（a）的热处理工艺：618K（345oC）保温2小时，然后用2小时升温

到803K保温12小时，

（b）的热处理工艺: 618K（345oC）保温14小时，然后用2小时升

温到803K, 淬入冷水中， 时效温度为450K

方框为Mg-4Zn，Mg-4Zn-Zr（菱形），Mg-4Zn-0.35Ca（十字） Mg-4Zn-0.35Ca-Zr（三角形），Mg-0.35Ca（圆形）

在Mg-Zn二元合金中析出的四方棒状1’（长轴平行于0001方向）和六角盘状的2’（大面平行于镁基体的基面）具有相同的成分

Another classic precipitation-hardenable system is the Mg-Zn system in the composition range of the 3-8 wt% zinc

新合金设计：

首先研究Mg-Ca-Zn合金，初步确定合金成分：

Mg-2Ca-5Zn

此合金中可能产生的相：-Mg，Mg2Ca，Ca2Mg6Zn3， 还有可能会析出Mg-Zn二元系沉淀相（β1’, β2’） 同时考虑Zn含量对合金热裂性的影响。

采用ThermoCalc 软件计算此合金的平衡相同及各相析出的体积分数。 采用Material Studio 计算相稳定性及各相的析出顺序