<PAGE>   1
                                                                      EXHIBIT 4b
      
            FIRST AMENDMENT TO AMENDED AND RESTATED CREDIT AGREEMENT
            --------------------------------------------------------

                  THIS FIRST AMENDMENT TO AMENDED AND RESTATED CREDIT AGREEMENT,
dated as of December 30, 1996 ("Amendment"), by and among Brush Wellman Inc., an
Ohio corporation ("Borrower"), the banks that are parties to this Amendment (the
"Banks"), and National City Bank, as agent for the Banks (in that capacity,
"NCB-Agent"),

                                WITNESSETH THAT:
                                ----------------

                  WHEREAS, Borrower, the Banks and NCB-Agent entered into an
Amended and Restated Credit Agreement, dated as of December 13, 1994 (together
with all Exhibits and Schedules thereto, the "Credit Agreement"), under which
the Banks, subject to certain conditions, agreed to lend to Borrower up to
$50,000,000 from time to time in accordance with the terms thereof; and

                  WHEREAS, the parties desire to amend the Credit Agreement as 
set forth herein;

                  NOW, THEREFORE, in consideration of the premises and the
mutual covenants and agreements contained herein, the parties hereto agree as
follows:

                  1.       Effect of Amendment; Definitions.
                           ---------------------------------
                  The Credit Agreement shall be and hereby is amended as
provided in Section 2 hereof. Except as expressly amended in Section 2 hereof,
the Credit Agreement shall continue in full force and effect in accordance with
its respective provisions on the date hereof. As used in the Credit Agreement,
the terms "Credit Agreement", "Agreement", "this Agreement", "herein",
"hereinafter", "hereto", "hereof", and words of similar import shall, unless the
context otherwise requires, mean the Credit Agreement as amended and modified by
this Amendment.

                  2.       Amendments.
                           -----------
                  (A) Subsection 3B.02 of the Credit Agreement shall be amended
by deleting the same and substituting in lieu thereof the following:

                  "3B.02 LEVERAGE. Borrower will not suffer or permit the
Companies' Funded Indebtedness at any time to exceed an amount equal to the
Leverage Multiplier (as hereinafter defined) times the Companies' EBITDA for the
four consecutive fiscal quarters most recently ended, all as determined on a
consolidated basis. As used herein, "Leverage Multiplier" means (i) from the
date of this Agreement to December 31, 1998, inclusive, 3.00, and (ii) on and
after January 1, 1999, 2.75."


<PAGE>   2

                  (B) Subsection 3B.03 of the Credit Agreement is hereby 
deleted and shall be left intentionally blank.

                  (C) Subsection 3B.04 of the Credit Agreement shall be amended
by deleting the same and substituting in lieu thereof the following:

                  "3B.04 INTEREST COVERAGE. Borrower will not at any time suffer
or permit the ratio (the "Interest Coverage Ratio") of (a) the aggregate of the
EBITDA of the Companies for the four consecutive fiscal quarters most recently
ended, to (b) the aggregate Interest Expense of the Companies for that period,
to be less than 5.00 to 1.00, all as determined on a consolidated basis."

                  (D) Subsection 3B.05 of the Credit Agreement shall be amended
by deleting the same and substituting in lieu thereof the following:

                  "3B.05 FUNDED INDEBTEDNESS. Borrower will not suffer or permit
the Funded Indebtedness of the Companies, at any time, to exceed an amount equal
to the Required Multiplier (as hereinafter defined) times the sum of the Funded
Indebtedness of the Companies plus the Tangible Net Worth of the Companies, all
as determined on a consolidated basis. As used herein, "Required Multiplier"
means (i) from the date of this Agreement to December 31, 2000, inclusive, 0.50,
and (ii) on and after January 1, 2001, 0.45 (provided, however, that Borrower
acknowledges and agrees that the inclusion in this Subsection of dates that are
beyond the current Expiration Date is not intended to supersede Subsection
2A.05, does not constitute an extension of the Expiration Date to or beyond
those dates, and does not obligate the Banks to extend the Expiration Date to or
beyond those dates).

                  (E) Subsection 3D.01(iv) of the Credit Agreement shall be
amended by deleting the same and substituting in lieu thereof the following:

                  "(iv)    any Guaranty by Borrower of Funded Indebtedness of 
                           any Company otherwise permitted by this Agreement,"

                  (F) Subsection 3D.02 of the Credit Agreement shall be amended
by deleting the same and substituting in lieu thereof the following:

                  "3D.02 BORROWINGS. No Company will create, assume or have
outstanding at any time any Indebtedness for Borrowed Money or any Funded
Indebtedness of any kind if after giving effect to such Indebtedness for
Borrowed Money or Funded Indebtedness, Borrower would be in non-compliance with
any of the 

                                      -2-


<PAGE>   3

financial standards set forth in Subsections 3B.01 to 3B.05, inclusive."

                  (G) Subsection 3D.03(vi) of the Credit Agreement shall be
amended by deleting the same and substituting in lieu thereof the following:

                  "(vi) any lease, other than any capitalized lease (it being
                  agreed that a capitalized lease is a lien rather than a lease
                  for the purposes of this Agreement) or the Master Lease
                  Agreement or the Port Authority Lease, so long as the
                  aggregate annual rentals under all such leases of all the
                  Companies do not exceed six million five hundred thousand
                  dollars ($6,500,000),"

                  (H) Subsection 3D.04 of the Credit Agreement shall be amended
by deleting the same and substituting in lieu thereof the following:

                  "3D.04   EQUITY TRANSACTIONS.  No Company will

                  (i)  be a party to any merger or consolidation, or

                  (ii) be or become a party to any joint venture or partnership,
         or make or keep any investment in any other stocks or other equity
         securities of any kind or otherwise acquire all or substantially all of
         the assets of another person, except that this clause (ii) shall not
         apply to (A) Borrower's existing investments in the stocks and other
         equity securities of existing or future Subsidiaries, (B) any other
         investment reflected in Borrower's Most Recent 4A.04 Financial
         Statements, or (C) acquisitions of assets of persons or equity
         investments made in persons, other than Subsidiaries, after the date of
         this Agreement in an aggregate amount, excluding investments permitted
         by Subsection 3D.01, not to exceed forty-five million dollars
         ($45,000,000) in the aggregate during any fiscal year of Borrower,
         provided, that of that amount not more than twenty million dollars
         ($20,000,000) in the aggregate is paid by the Companies in cash during
         any fiscal year, or

                  (iii) lease as lessor, sell, sell-leaseback or otherwise
         transfer (whether in one transaction or a series of transactions) all
         or any substantial part of its fixed assets (other than in respect of
         the Port Authority Lease and chattels that shall have become obsolete
         or no longer useful in its present business with a fair market value
         not exceeding ten million dollars ($10,000,000) in the aggregate during
         any fiscal year), or the capital stock of any Subsidiary of 


                                      -3-
<PAGE>   4


          Borrower (other than the sale of all of the capital stock of one or
          more Subsidiaries of Borrower that own assets with a fair market value
          not exceeding ten million dollars ($10,000,000) in the aggregate
          during any fiscal year so long as no Bank, within ten (10) Banking
          Days of receipt of notice of the proposed sale, notifies Borrower in
          writing that such Bank believes the proposed sale could have a
          Material adverse effect on the consolidated financial condition of the
          Companies);

PROVIDED, that if no Default or Potential Default shall then exist and if none
would thereupon begin to exist, this Subsection 3D.04 shall not apply (A) to any
merger or consolidation of any Subsidiary of Borrower with any other Subsidiary
of Borrower so long as a Subsidiary of Borrower is the surviving entity or to
any merger or consolidation of any wholly owned Subsidiary of Borrower with
Borrower so long as Borrower is the surviving corporation, or (B) to any
dissolution and liquidation of a Subsidiary of Borrower, or any transfer of
assets between Subsidiaries of Borrower or from any Subsidiary of Borrower to
Borrower."

                  (I) Subsection 5A.04 of the Credit Agreement shall be amended
by deleting the same and substituting in lieu thereof the following:

                  "5A.04 CROSS-DEFAULT. If, in respect of any existing or future
Indebtedness for Borrowed Money (regardless of maturity) or Funded Indebtedness
now owing or hereafter incurred by Borrower or any Subsidiary of Borrower, there
should occur or exist under its original provisions (except for any amendment
made prior to the date of this Agreement but without giving effect to any
amendment, consent or waiver after the date of this Agreement) any event,
condition or other thing which constitutes, or which with the giving of notice
or the lapse of any applicable grace period or both would constitute, a default
which accelerates (or permits any creditor or creditors or representative
thereof to accelerate) the maturity of any Indebtedness for Borrowed Money or
Funded Indebtedness; or if any Indebtedness for Borrowed Money (regardless of
maturity) or Funded Indebtedness (other than any payable on demand) shall not be
paid in full at its stated maturity; or if any Indebtedness for Borrowed Money
or Funded Indebtedness payable on demand shall not be paid in full on demand
therefor."

                  (J) Section 9 of the Credit Agreement shall be amended as
follows:

                  (1) The definition of "Funded Indebtedness" is amended by
deleting the same and inserting the following in lieu thereof:

                                      -4-
<PAGE>   5

                  "FUNDED INDEBTEDNESS of a person shall mean, without 
duplication:

                  (a)      all Indebtedness for Borrowed Money of such person
                           and all other obligations of such person for the
                           deferred purchase price of property or services
                           (including, without limitation, all obligations
                           contingent or otherwise of such person in connection
                           with acceptance, letter of credit or similar
                           facilities and in connection with any agreement to
                           purchase, redeem or otherwise acquire for value any
                           capital stock of such person, or agreement to
                           purchase, redeem or otherwise acquire for value any
                           rights or options to acquire such capital stock, now
                           or hereafter outstanding);

                  (b)      all indebtedness created or arising under any sale
                           and leaseback arrangement, conditional sale or other
                           title retention agreement with respect to property
                           owned or acquired by such person (whether or not the
                           rights and remedies of the seller or lender under
                           such agreement in the event of default are limited to
                           repossession or sale of such property);

                  (c) All obligations secured by a Lien on property owned by
         such person (whether or not assumed) (without regard to any limitation
         of the rights and remedies of the holder of such Lien or the lessor
         under any lease to repossession or sale of such property); and

                  (d) All obligations of such person under a product financing
         or similar arrangement described in paragraph 8 of FASB Statement of
         Accounting Standards No. 49 or any similar requirement of GAAP;"

                  (2)  The definition of "Guarantor" is amended by deleting the
same and inserting the following in lieu thereof:

                  "GUARANTOR means any person that is liable for any Contingent
                  Obligation; and Guaranty or guaranty means the obligation of a
                  Guarantor; provided, however, that the amount of any Guaranty
                  shall be deemed to be equal to the outstanding amount of the
                  obligation that is guaranteed thereby or such lesser amount to
                  which the maximum exposure of the Guarantor may be
                  contractually limited in writing;"

                  (3) The definition of "Tangible Net Worth" is amended by
deleting the same and inserting the following in lieu thereof:

                  "TANGIBLE NET WORTH means (a) book net worth, less (b) such
                  assets of the Companies, on a consolidated basis, 


                                      -5-

<PAGE>   6

                    as consist of good will, costs of businesses over net assets
                    acquired, patents, copyrights, trademarks, mailing lists,
                    catalogues, bond discount, underwriting expense,
                    organizational expenses and intangibles (except that
                    intangibles such as treasury stock which shall have already
                    been deducted from book net worth shall not be deducted
                    again), all as determined on a consolidated basis in
                    accordance with GAAP;"

                  (4)  The following definitions shall be inserted in 
alphabetical order:

                  "CONTINGENT OBLIGATION means any direct or indirect liability,
contingent or otherwise, with respect to any Funded Indebtedness, lease,
dividend, letter of credit, banker's acceptance or other obligation of another
person incurred to provide assurance to the obligee of such obligation that such
obligation will be paid or discharged, that any agreements relating thereto will
be complied with, or that the holders of such obligation will be protected (in
whole or in part) against loss in respect thereof;

                  EBIT means for any period, with respect to Borrower and its
                  Subsidiaries, the sum of (a) the Net Income for such period,
                  plus (b) the Interest Expense for such period, plus (c)
                  charges against income for taxes for such period, all on a
                  consolidated basis;

                  EBITDA means for any period, with respect to Borrower and its
                  Subsidiaries, the sum of (a) EBIT plus (b) the charges against
                  income for depreciation for such period plus (c) the charges
                  against income for amortization for such period, plus (d)
                  other non-cash charges for such period, minus (e) any and all
                  non-cash credits to Net Income, all as determined on a
                  consolidated basis in accordance with GAAP;

                  INDEBTEDNESS FOR BORROWED MONEY OR INDEBTEDNESS FOR BORROWED
MONEY of a person shall mean at any time, all indebtedness required by GAAP to
be reflected as indebtedness on such person's balance sheet, including as
appropriate, all indebtedness (i) in respect of any money borrowed; (ii) under
or in respect of any Contingent Obligation (whether direct or indirect) of any
money borrowed; (iii) evidenced by any loan or credit agreement, promissory
note, debenture, bond, or other similar written obligation in respect of
borrowed money; or (iv) arising under any lease that is, or is required under
GAAP to be, capitalized on the balance sheet of such person at such time or any
lease that is a Synthetic Lease;

                  INTEREST EXPENSE means, for any period, with respect to
                  Borrower and its Subsidiaries, the aggregate amount of
                  interest expense for such period on the aggregate principal
                  amount of any Funded Indebtedness, including capitalized
                  interest, as determined on a consolidated basis in accordance
                  with GAAP;

                                      -6-
<PAGE>   7

                  MASTER LEASE AGREEMENT means the Master Lease Agreement, dated
                  as of December 30, 1996, between Borrower and National City
                  Bank, for itself and as agent for certain participants,
                  relating to the lease of certain items of equipment, as the
                  same may be amended or modified from time to time;

                  PORT AUTHORITY LEASE means the Lease, dated as of October 1,
                  1996, between the Toledo-Lucas County Port Authority, as
                  lessor, and Borrower, as lessee, relating to certain real and
                  personal property located at 14710 West Portage River S. Road,
                  Harris Township, Ohio 43416, as the same may be amended or
                  modified from time to time;

                  SYNTHETIC LEASE means any lease that is considered a financing
                  for federal income tax purposes, but is considered an
                  operating lease for purposes of GAAP, including, without
                  limitation, the Master Lease Agreement;"

                  3.       Representations and Warranties.
                           -------------------------------
                  (A) Borrower hereby represents and warrants to the Banks and
NCB-Agent that all representations and warranties set forth in the Credit
Agreement, as amended hereby, are true and correct in all material respects, and
that this Amendment and the subject notes have been executed and delivered by a
duly authorized officer of Borrower and constitute the legal, valid and binding
obligation of Borrower, enforceable against Borrower in accordance with their
respective terms.

                  (B) The execution, delivery and performance by Borrower of
this Amendment and its performance of the Credit Agreement and the subject notes
have been authorized by all requisite corporate action and will not (1) violate
(a) any order of any court, or any rule, regulation or order of any other agency
of government, (b) the Articles of Incorporation, the Code of Regulations or any
other instrument of corporate governance of Borrower, or (c) any provision of
any indenture, agreement or other instrument to which Borrower is a party, or by
which Borrower or any of its properties or assets are or may be bound; (2) be in
conflict with, result in a breach of or constitute, alone or with due notice or
lapse of time or both, a default under any indenture, agreement or other
instrument referred to in (1)(c) above; or (3) result in the creation or
imposition of any lien, charge or encumbrance of any nature whatsoever.

                  4.       Miscellaneous.
                           -------------
                  (A) This Amendment shall be construed in accordance with and
governed by the laws of the State of Ohio, without 

                                      -7-
<PAGE>   8

reference to principles of conflict of laws. Borrower agrees to pay on demand
all costs and expenses of the Banks and NCB-Agent, including reasonable
attorneys' fees and expenses, in connection with the preparation, execution and
delivery of this Amendment.

                  (B) The execution, delivery and performance by the Banks and
NCB-Agent of this Amendment shall not constitute, or be deemed to be or
construed as, a waiver of any right, power or remedy of the Banks or NCB-Agent,
or a waiver of any provision of the Credit Agreement. None of the provisions of
this Amendment shall constitute, or be deemed to be or construed as, a waiver of
any "default under this Agreement" or any "event of default," as those terms are
defined in the Credit Agreement.

                  (C) This Amendment may be executed in two or more
counterparts, each of which shall constitute an original, but all of which, when
taken together, shall constitute but one instrument.

                  IN WITNESS WHEREOF, the parties have caused this Amendment to
be duly executed as of the day and year first above written.

Address:                                 BRUSH WELLMAN INC.
         17876 St. Clair Avenue
         Cleveland, Ohio 44110
                                         By:
                                            -----------------------------------

                                         Title:
                                               --------------------------------

Address:                                 NATIONAL CITY BANK,
   Deliveries:                           for itself and as Agent
         Metro/Ohio Division
         1900 East Ninth Street
         Cleveland, Ohio 44114-3484      By:
         Fax:  (216) 575-9396               -----------------------------------
                                         Title:
                                               --------------------------------
         Mail:
         Metro/Ohio Division
         P.O. Box 5756
         Cleveland, Ohio 44101


Address:                                 KEYBANK NATIONAL ASSOCIATION

         127 Public Square
         Cleveland, Ohio 44114           By:
                                            -----------------------------------

                                         Title:
                                               --------------------------------

                                      -8-
<PAGE>   9

Address:                                  THE BANK OF NOVA SCOTIA
         600 Peachtree St., NE
         Suite 2700
         Atlanta, Georgia 30308            By:
                                              ---------------------------------
                                           Title:
                                                 ------------------------------


Address:                                   FIRST CHICAGO NBD BANK, N.A.

         611 Woodward
         Detroit, Michigan 48226            By:
                                               --------------------------------

                                            Title:
                                                  -----------------------------