问题 问答题 简答题

简述影响再结晶退火组织晶粒大小的因素。

答案

参考答案:

①预变形量。预变形量增大,则晶核的形成速率N和其随后的长大线速度G同时都增大,但由于N增大率大于G增加率,其结果将使N/G加大(G/N减小),可取得细化晶粒的效果。

②原始晶粒尺寸。当预变形量一定时,原始晶粒越小,则再结晶后晶粒便越细。

③退火温度。再结晶晶粒度受温度的影响很小。

④杂质。杂质可以起细代晶粒的作用。

⑤形变瘟度。预形变时温度越高,则回复程度越大,储存能减小,N与G的驱动力下降,晶粒尺寸也就随之而增大。

阅读理解

阅读理解。

     Everything has a name. All people, places and things have names. For example, Jenny is the name of a

student from England. England is the name of her country. Cities and towns have names, too. Schools and

office building also have names. All things have names. Names are important.

     Names are different all over the world. In Jenny's class, Jenny must learn the names of students from all

over the world. This is very difficult because the names are different.

     In the USA, most people have a first name, a middle name, and a last name. Parents choose the first and

middle names for their baby. There are names for boys and names for girls. For example, John, Peter, Tom

and Mike are all names for boys. Elizabeth, Betty, Susan, and Mary are all names for girls. The last name is

the family name. Usually it is the father's family name. In a family, the mother, the father, and the children

usually have the same last name.

     Names are different all over the world. They can be long or short, but they are always very important.

1. Why does everything have a name? Because _____. [ ]

A. it is very interesting to have a name

B. it is very easy to be remembered

C. it is very easy to be told from others

D. both B and C

2. It is difficult to learn names all over the world because _____. [ ]

A. there are many different languages

B. the names in different countries are different

C. some names are very short, some are very long

D. there are many names all over the world

3. Which of the following is true? [ ]

A. It's difficult to learn the names because they are different.

B. There is no difference between girls' names and boys' names.

C. Jenny doesn't want to learn the names very well.

D. It's easy for Jenny to learn the names of her classmates.

4. What names are for girls? [ ]

A. George, Linda, Susan

B. Tom, Jill, Candy

C. Elizabeth, Betty, Mary

D. Peter, Jeff, Jack

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